Category: 2nd PUC

You can Download 2nd PUC Kannada Workbook Answers Pallava Chapter 2 Samanarthaka Galu, 2nd PUC Kannada Textbook Answers, Karnataka State Board Solutions help you to revise complete Syllabus and score more marks in your examinations.

Karnataka 2nd PUC Kannada Workbook Answers Pallava Chapter 2 Samanarthaka Galu

You can Download Chapter 16 Chemistry in Everyday Life Questions and Answers, Notes, 2nd PUC Chemistry Question Bank with Answers Karnataka State Board Solutions help you to revise complete Syllabus and score more marks in your examinations.

Karnataka 2nd PUC Chemistry Question Bank Chapter 16 Chemistry in Everyday Life

2nd PUC Chemistry Chemistry in Everyday Life NCERT Textbook Questions

Question 1.
Why do we need to classify drugs in different ways?
Answer:
The classification of drugs and the reason for classification are as follows:
1. On the basis of pharmacological effect: This classification provides doctor the whole range of drugs available for the treatment of a particular type of problem Hence, such a classification is very useful to doctors.

2. On the basis of drug action: This classification is based on the action of a drug on a particular biochemical process Thus, this classification is important.

3. On the basis of chemical structure: This classification provides the range of drugs sharing common structural features and often having similar pharmacological activity.

4. On the basis of molecular targets: This classification provides medicinal chemists the drugs having the same mechanism of action on targets Hence, is the most useful to medicinal chemists.

Question 2.
Explain the term, target molecules or drug targets as used in medicinal chemistry
Answer:
In medicinal chemistry, drug targets refer to the key molecules involve in certain metabolic pathways that result in specific diseases Carbohydrates, proteins, lipids, and nucleic acids are example of drug targets.

Drugs are chemical agents designed to inhibit these target molecules by binding with the active sites of the key molecules.

Question 3.
Name the macromolecules that are chosen as drug targets
Answer:
The macromolecules chosen as drug targets are carbohydrates, lipids, proteins and nucleic acids.

Question 4.
Why should not medicines be taken without consulting doctors?
Answer:
A medicine can bind to more than one receptor site, thus a medicine may be toxic for some receptor site Further, in most cases, medicines cause harmful effects when taken in higher dose than recommended As a result, medicines may be poisonours in such cases Hence, medicines should not be taken without consulting doctors.

Question 5.
Define the term chemotherapy
Answer:
The use of chemicals for therapeutic effect is called chemotherapy For example the use of chemicals in the diagnosis, prevention, and treatment of diseases.

Question 6.
Which forces are involved in holding the drugs to the active site of enzymes?
Answer:
Either of the following forces can be involved in holding drugs to the active sites of enzymes.

• Ionic bonding
• Hydrogen bonding
• Dipole-dipole interaction
• Van der Waals forces

Question 7.
While antacids and antiallergic drugs interfere with the function of histamines, why do these not interfere with the function of each other ?
Answer:
Specific drugs affect particular receptors Antacids and anti-allergic drugs work at different receptors This is the reason why antacids and anti-allergic drugs do not interfere with each others functions, but interfere with the functions of histamines.

Question 8.
Low level of noradrenaline is the cause of depression What type of drugs are needed to cure this problem? Name two drugs
Answer:
Anti-depressant drugs are needed to counteract the effect of depression These drugs inhibit enzymes catalysing the degradation of the neurotransmitters, nor adrenaline As a result, the important neurotransmitters is slowly metabolised and then it can activate its receptor for longer periods of time.
Two anti-depressant drugs are:

1. Iproniazid
2. Phenelzine

Question 9.
What is meant by the term ‘broad spectrum antibiotics? Explain
Answer:
Antibiotics that are effective against a wide range of gram-positive and gram-negative bacteria are known as broad spectrum antibiotics, chloramphenicol is a broad spectrum antibiotics.

It can be used for the treatment of typhoid, dysentery, acute fever, pneumonia, meningitis, and certain forms of urinary infections Two other broad spectrum antibiotics are vancomycin and ofloxacin Ampicillin and amoxycillin-synthetically modified from penicillin – are also broad spectrum antibiotics

Question 10.
How do antiseptics differ from disinfectants ? Give one example of each
Answer:
Antiseptics and disinfectants are effective against micro-organisms However antiseptics are applied to the living tissues such as wounds, cuts, ulcers, and diseased skin surfaces, while disinfectants are applied to inanimate objects such as floors, drainage system, instruments, etc Disinfectants are harmful to the living tissues.

Iodine is an example of a strong antiseptic Tincture of iodine (2-3 percent of solution of iodine in alcohol – water mixture) is applied to wounds 1 percent solution of phenol is used as a disinfectant.

Question 11.
Why are cimetidine and ranitidine better antacids than sodium hydrogen carbonate or magnesium or aluminium hydroxide ?
Answer:
Antacids such as sodium hydrogen carbonate, magnesium hydroxide, and aluminium hydroxide work by neutralising the excess hydrochloric acid present in the stomach However, the root cause for the release of excess acid remains untreated.

Cimetidine and ranitidine are better antacids as they control the root cause of acidity These drugs prevent the interaction of histamine with the receptors present in the stomach walls Consequently there is a decrease in the amount of acid release by the stomach This is why cimetidine and ranitidine are better antacids than sodium hydrogen carbonate, magnesium hydroxide, and aluminium hydroxide.

Question 12.
Name a substance which can be used as an antiseptic as well as disinfectant
Answer:
Phenol can be used as an antiseptic as well as a disinfectant 0.2 percent solution of phenol is used as an antiseptic, while 1 percent of its solution is used as a disinfectant.

Question 13.
What are the main constituents of dettol?
Answer:
The main constituents of dettol are chloroxylenol and α -terpineol

Question 14.
What is tincture of iodine? What is its use?
Answer:
Tincture of iodine is a 2-3 percent solution of iodine in alcohol-water mixture It is applied to wounds as an antiseptic.

Question 15.
What are food preservatives ?
Answer:
Food preservatives are chemicals that prevent food from spoilage due to microbial growth Table salt, sugar, vegetable oil, sodium benzoate (C₆H₃ COONa), and salts of propanoic acid are some examples of food preservatives.

Question 16.
Why is use of aspartame limited to cold foods and drinks?
Answer:
Aspartame becomes unstable at cooking temperature This is the reason why its use is limited to cold foods and drinks.

Question 17.
What are artificial sweetening agents ? Give two examples
Answer:
Artificial sweetening agents that sweeten food However, unlike natural sweeteners, they do not add calories to our body They do not harm the human body Some artificial sweeteners are aspartame, saccharin, sucralose, and alitame.

Question 18.
Name the sweetening agent used in the preparation of sweets for a diabetic patient
Answer:
Artificial sweetening agents such as saccharin, alitame, and aspartame can be used in preparing sweets for diabetic patients.

Question 19.
What problem arises in using alitame as artificial sweetener ?
Answer:
Alitame is a high potency sweetener It is difficult to control the sweetness of food while using alitame as an artificial sweetener.

Question 20.
How are synthetic detergents better than soaps?
Answer:
Soaps work in soft water, they are not effective in hard water In contrast synthetic detergents work both in soft water and hard water Therefore, synthetic detergents are better than soaps.

Question 21.
Explain the following terms with suitable examples
(i) cationic detergents
(ii) anionic detergents and
(iii) non-ionic detergents
Answer:
(i) Cationic detergents:
Cationic detergents are quarternary ammonium salts of acetates, chlorides, bromides This are called cationic detergents because the

Question 22.
What are biodegradable and non- biodegradable detergents ? Give one example of each
Explain the cleansing action of soaps
Answer:
Detergents that can be degraded by bacteria are called biodegradable detergents Such detergents have straight hydrocarbon chains For example: Sodium Lauryl sulphate.

Detergents that cannot be degraded have highly branched hydrocarbon chains For example: Sodium – 4- (1, 3, 5,7 – tetra methyl octyl) benzene sulphonate.

Soap molecules form micelles around an oil droplet (dirt) in such a way that the hydrophobic parts of the stearate ions attach themselves to the oil droplet and the hydrophilic parts project outside the oil droplet Due to the polar nature of the hydrophilic parts, the stearate ions (along with the dirt) are pulled into water, thereby removing the dirt from the cloth.

Question 23.
Why do soaps not work in hard water?
Answer:
Soaps are sodium or potassium salts of long-chain fatty acids Hard water contains calcium and magnesium ions When soaps are dissolved in hard water, these ions displace sodium or potassium from their salts and form insoluble calcium or magnesium salts of fatty acids The insoluble salts separate as scum.

this is the reason why soaps do not work in hard water.

Question 24.
Can you use soaps and synthetic detergents to check the hardness of water?
Answer:
Soaps get precipitated in hard water, but not in soft water Therefore, soaps can be used for checking the hardness of water However, synthetic detergents do not get precipitated either cationic part of these detergents contains a long hydrocarbon chain and a positive charge on the N atom
For example:

1. Anionic detergents: Anionic detergents are of two types
(a) Sodium alkyl sulphates: These detergents are sodium salts of long chain alcohols, they are prepared by first treating these alcohols with concentrated sulphuric acid and then with sodium hydroxide Examples of these detergents include sodium lauryl sulphate (C₁₁H₂₃CH₂OSO₃ Na⁺) and sodium stearyl sulphate (C₁₇H₃₅CH₂OSO₃ Na⁺)

(b) Sodium alkyl benzene sulphonates: These detergents are sodium salts of long chain alkyl benzene sulphonic acids They are prepared by Friedd-crafts alkylation of benzene with long chain alkyl halides or alkenes The obtained product is first treated with concentrated sulphuric acid and then with in sodium hydroxide Sodium 4 – (1 – dodecy) benzene sulphonate (SDS) is an example of anionic detergents.

2. Non-ionic detergents Molecules of these detergents do not contain any ions These detergents are esters of alcohols having high molecular mass They are obtained by reacting polyethylene glycol and stearic acid.

Question 25.
If water contains dissolved calcium hydrogen carbonate, out of soaps and synthetic detergents which one will you use for cleaning clothes?
Answer:
Synthetic detergents are preferred for cleaning clothes When soaps are dissolved in water containing calcium ions, these ions form insoluble salts that are of no further use, however when synthetic detergents are dissolved in water containing calcium ions, these ions from soluble salts that act as cleaning agents.

Question 26.
Label the hydrophilic and hydrophobic parts in the following compounds

Answer:

Question 27.
Sleeping pills are recommended by doctors to the patients suffering from sleeplessness but it is not advisable to make its dose without consultation with the doctor, Why?
Answer:
Most drugs when taken in doses higher than recommended may carry harmful effects and sometimes, may even lead to death Hence, a doctor should always be consulted before taking any medicine.

Question 28.
With reference to which classification has the statement, “ranitidine is an antacid” been given?
Answer:
The given statement refers to the classification of pharmacological effects of the drug This is because any drug that is used to counteract the effects of excess acid in the stomach is called an antacid.

Question 29.
Why do we require artificial sweetening agents
Answer:
A large number of people are suffering from diseases such as diabetes and obesity These people cannot take normal sugar ie sucrose as it is harmful for them Therefore artificial sweetening agents that do not add to the caloric intake of a person are required, Saccharin, aspartame, and ulitame are a few examples of artificial sweeteners.

Question 30.
Write the chemical equation for preparing sodium soap from glyceryl oleate and glyceryl palmitate Structural formulas of these compounds are given below
1. (C₁₅H₃₁COO)₃C₃H₅ – Glyceryl Palmitate
2. (C₁₇H₃₃COO)₃C₃H₅ – Glyceryl oleate
Answer:
1.

2.

Question 32.
Following type of non-ionic detergents are present in liquid detergents, emulsifying agents and wetting agents Label the hydrophilic and hydrophobic parts in the molecule Identify the functional group (s) present in the molecule
Answer:

Functional groups present in the molecule are:

• Ether, and
• primary alcoholic group.

 2nd PUC Chemistry Chemistry in Everyday Life Additional Questions

Question 1.
In order to wash clothes with water containing dissolved calcium hydrogen carbonate, which cleaning agent will you prefer and why: Soaps or synthetic detergents? Give one advantage of soaps – over synthetic detergents
Answer:
Water containing calcium hydrogen carbonate is hard water Detergents are preferred over soaps for cleaning clothes in hard water because calcium salts of detergents are soluble in water while calcium salts of soaps are insoluble As a result, lot of soap is wasted

Disadvantage of using detergents: Soaps are biodegradable while detergents having branched hydrocarbon chains are not biodegradable and hence cause water pollution in rivers and waterways.

Question 2.
Account for following
(i) Aspirin drug helps in prevention of heart attack
Answer:
Most of the heart attacks are due to blood clotting in the coronary arteries Aspirin helps to make the blood thinner and thus prevents the formation of blood clots in the coronary arteries thereby preventing heart attacks.

Question 3.
What are antihistamine? Give two examples
Answer:
Antihistamines are drugs which either reduce or inhabit the action of histamine in the body thereby preventing allergy Two important antihistamines are brompheniramine and terfenadine

Mode of action: Histamines interact with the binding sites of receptor in the body to produce allergy Antihistamines compete with histamines for these binding sites of receptor and thus do not allow histamine to produce allergy.

Question 4.
How does aspirin act as analgesic?
Answer:
Aspirin inhibits the synthesis of erostaglandis which stimulate inflammation of the tissue and cause pain.

Question 5.
What are barbiturates? To which class of drugs do they belong?
Answer:
55 derivatives of barbituric acid are called barbiturates They belong to class of tranquilizers.

Question 6.
What is salvarsan? To which class of drugs do they belong?
Answer:
Salvarsan is an antimicrobial agent It is used for the treatment of disease called syphillis

Question 7.
Give one example of artificial sweetner used by diabetic patients
Answer:
Saccharin (in form of sodium salt) is taken as artificial sweetner by diabetic patients.

Question 8.
Define a tranquilizer
Answer:
Tranquilizers are drugs which act on central nervous system to help in reducing anxiety.

Question 9.
What is the nature of an antacid?
Answer:
Substances which reduce the release of excess HCl by preventing the interaction of histamine with the receptors present in the stomach wall are called antacids Examples cimetidine and ranitidine.

Question 10.
Which alkaloid is used for
1. hypertension
2. malaria fever?
Answer:
1. Reserpine
2. Quinine

You can Download 2nd PUC Kannada Workbook Answers Pallava Chapter 1 Padyagala Bhavartha Rachane, 2nd PUC Kannada Textbook Answers, Karnataka State Board Solutions help you to revise complete Syllabus and score more marks in your examinations.

Karnataka 2nd PUC Kannada Workbook Answers Pallava Chapter 1 Padyagala Bhavartha Rachane

You can Download Chapter 1 Electric Charges and Fields Questions and Answers, Notes, 2nd PUC Physics Question Bank with Answers, Karnataka State Board Solutions help you to revise complete Syllabus and score more marks in your examinations.

Karnataka 2nd PUC Physics Question Bank Chapter 1 Electric Charges and Fields

2nd PUC Physics Electric Charges and Fields NCERT Text Book Questions and Answers

Question 1.
What is the force between two small charged spheres having charges of
2× 10^-7 and 3 x 10^-7 C placed 30cm apart in air?
Answer:

Question 2.
The electrostatic force on a small sphere of charge 0.4 µ C due to another small sphere of charge – 0.8 µ C in air is 0.2 N.
(a) What is the distance between the two spheres ?
(b) What is the force on the second sphere due to the first?
Answer:

Question 3.
Check that the ratio ke²/Gm_e m_p is dimensionless. Look up a table of Physical constants and determine the value of this ratio. What does the ratio signify?
Answer:

This value represents the ratio of electrostatic force of gravitational force between an electron and a proton.

Question 4.
(a) Explain the meaning of the statement ‘electric charge of a body is quantised’,
(b) Why can one ignore quantisation of electric charges when dealing with macroscopic i.e large scale charges?
Answer:
(a) The magnitude of charge on a proton or an electron (e = 1.6 x 10¹⁹c) is called elementary charge. Since protons and electrons are only basic charged particles in a matter, the charge on an object must be integral multiple of ±e(1.6×10¹⁹c),
i.e. the charge possessed by an object cannot be a fraction of + e. Mathematically, the charge on any matter must be equal to q = ±ne, where n is an integer.

(b) In practice, the charge on any charged body is very large. On the other hand, the charge on an electron is very small. When electrons are added to a body (negatively charged body) or removed from a body (positively charged body), the change taking place in the total charge on the body is so small that the charge seems to be varying in a continuous manner. Therefore quantisation of electric charge can be ignored, when dealing with a large scale charged body.

Question 5.
When a glass rod is rubbed with a silk cloth, charges appear on both. A similar phenomenon is observed with many other pairs of bodies. Explain how this observation is consistent with the law of conservation of charge.
Answer:
Before rubbing, both the glass rod and the silk cloth are electrically neutral. In other words, the net charge on the glass rod and the silk cloth is zero. When the glass rod is rubbed with silk cloth, a few electrons from the glass rod get transferred to the silk cloth. As a result, the glass rod becomes positively charged and the silk cloth negatively charged. Since the magnitude of positive charge on the glass rod is the same as that of negative charge on the silk, the net charge on the system is zero. Thus the appearances of charge on the glass rod and the silk cloth is in accordance with the law of conservation of charges.

Question 6.
Four point charges q_A = 2 µC, q_B = -5 µC, q_c = 2 µC and q_D = -5 µC are located at the corners of a square ABCD of side 10cm. What is the force of a charge of 1 µC placed at the centre of the square?
Answer:
Consider the square ABCD of each side 10cm and centre O. The charge of 1 µC is placed at point O. The charge of 1 µC is placed at point O.

equal and opposite forces due to the charges q_A and q_c. Similarly, the charges of 1 µC experiences equal and opposite forces F_fi and F_d due to the charges q_B and q_D.

Hence, the net force on the charge of 1 p C due to the given arrangement of the charges is zero.

Question 7.
(a) An electrostatic field line is a continuous curve. That is a Held line cannot have sudden breaks. Why not?
(b) Explain why two field lines never cross each other at any point?
Answer:
(a) The tangent at a point on the electric line of force tells the direction of electric field changes from point to point. Therefore the line of force are, generally, curved lines. Further, they are continuous curves and cannot have sudden breaks. For if it is so, it will indicate the absence of electric field at the breakpoints

(b) The tangents at a point on the line of force gives the direction of electric field at that point. If two lines of forces intersect each other at a point, then electric field at that point will have two directions. As the same cannot be true, two lines of force will never intersect each other.

Question 8.
Two point charges q_A = 3 µC and q_B = -3 µC are located 20 cm apart in vacuum.
(a) What is the electric field at the midpoint O of the line AB joining the two charges?
(b) If a negative test charge of magnitude 1.5×10^-9C is placed at this point, what is the force experienced by the test charge?
Answer:


The force on the negative charge acts in a direction opposite to that of the electric field.

Question 9
A system has two charges q_A = 2.5× 10^-7C and q_B = -2.5 x 10^-7C located at points
A: (0, 0, -15cm), respectively. What are the total charge and electric dipole moment of the system?
Answer:
The charges q_A and q_B are located at the points A (0,0, – 15cm) and B (0, 0, +15cm). B The points A and B lie on z-axis as shown.
It follows that,
AB = OA + OB = 30ci = 0.3m

Question 10.
An electric dipole with dipole moment 4×10^-9cm is aligned at 30° with the direction of a uniform electric field of magnitude 5 × 10⁴ NC¹. Calculate the magnitude of the torque acting on the dipole.
Answer:

Question 11.
A polythene piece rubbed with wool is found to have a negative charge of 3x 10 ⁷C
(a) Estimate the number of electrons transferred (from which to which ?)
(b) Is there a transfer of mass from wool to polythene?
Answer:
(a) The total charge transferred,
q = -3 x 10^-7C
charge on an electron, e = -1.6x 10¹⁹C From quantization of charge, q = ne Therefore, number of electrons transferred,

(b) Since electrons are transferred from wool to polythene, there is transfer of mass also. This is because electrons are material particles and possess mass (m_e = 9.1 x 10^-31kg).

Question 12
(a) Two insulated charged copper spheres A and B have their centres separated by a distance of 50 cm. What is the mutual force of electrostatic repulsion if the charge on each is 6.5 x 10^-7C ? The radii of A and B are negligible compared to the distance of separation.

(b) What is the force of repulsion if each sphere is charged double the above amount and the distance between them is halved?
Answer:
(a) Charge on sphere A, q₁, = 6.5 x 10^-7c
charge on sphere B, q₂ = 6.5 x 10 ⁷c
Distance between the spheres A and B, r = 50 cm= 0.5m

Question 13
Suppose the spheres A and B in exercise 1.12 have identical sizes. A third sphere of the same size but uncharged is brought in contact with the first, then brought in contact with the second, and finally removed from both. What is the new force of repulsion between A and B?
Answer:
The charge on A and B, q₁ = q₂ = 6.5x 10⁷C.
The distance between the spheres r = 0.5m. Since the spheres are same size, they will possess equal charges on being brought in contact. When uncharged sphere c (q₃ = 0) is bought in contact with A, charge left on A.

Question 14.
Fig 1.33 shows tracks of three charged particles in a uniform electrostatic field. Give the signs of the three charges. Which particle has the highest charge to mass ratio?

Answer:
Charges (1) and (2) are negative as they were attracted by the positive plate and charge (3) is positive as it is deflected towards negative plate.
Thus charge (3) has highest charge to mass ratio (as it would be a positive figure)

Question 15.
Consider a uniform electric Held \(\vec { E } =3\times { 10 }^{ 3 }\hat { i } { N }/{ C }\)
(a) What is the flux of this field through a spheres A and B, charges inside the box. Therefore, if the net outward flux is zero, we cannot conclude that the charge inside the box is zero. One can only say that the net charge inside the box is zero.

(b) A point charge +10 p C is a distance 5cm directly above the centre of a square of side 10cm, as shown in fig. 1.34. What is the magnitude of the electric flux through the square of 10cm on a side whose plane is parallel to the yz plane?
(b) What is the flux through the same square if the normal to its plane makes a 60° angle with the x-axis ?
Answer:

Question 16.
What is the net flux of the uniform electric field of exercise 1.15 through a cube of side 20cm oriented so that its faces are parallel to the coordinate planes?
Answer:


In each plane, there is a set two faces of the cube. Through one face, electric flux enters and through the other face, an equal flux leaves. Therefore, net flux through the cube,

Question 17.
Carefid measurement of the electric field at the surface of a black box indicates that the net outward flux through the surface of the box is 8.0 ×10³Nm²/C.
(a) What is the net charge inside the box?
(b) If the net outward flux through the surface of the box were zero, could you conclude that there were no charges inside the box? Why or why not?
Answer:

(b) If the net outward flux through the surface of the box is zero, it cannot be concluded that there is no charge inside the box. There may be equal amount of positive and negative charges inside the box. Therefore, if the net outward flux is zero, we cannot conclude that the charge inside the box is zero. One can only say that the net charge inside the box is zero.

Question 18.
A point charge +10 µ C is a distance 5cm directly above the centre of a square of side 10cm, as shown in fig. 1.34. What is the magnitude of the electric flux through the square?

Answer:

consider that the charge q is at a distance of 5 cm from the square ABCD of each side 10cm as shown. The square ABCD can be considered as one of the six faces of a cube of each side 10cm. Then according to Gauss’ theorem, total electric flux through all the six faces of the cube,

Question 19.
A point charge of 2 p C is at the centre of a cubic Gaussian surface 9cm on edge. What is the net electric flux through the surface?
Answer:
Here, q = 2µC = 2 × 10^-6C
side of cube, a = 9cm = 0.09 m
According to Gauss’ law, the net electric flux through all the six faces of the cube,

Question 20.
A point charge causes an electric flux of  1 x 10³Nm²/C to pass through a spherical Gaussian surface of a 10cm radius centred on the charge.
(a) If the radius of the Gaussian surface were doubted, how much flux would pass through the surface?
(b) What is the value of the point charge?
Answer:
Here φ = -1 x 10³Nm²C^-1
radius of Gaussian surface, r = 10cm = 0. 1m.
(a) If the radius of the gaussian surface is doubled, the electric flux through the new surface will still remain the same i.e. -1 x 10³Nm²C^-1
This is because the same charge is enclosed by the gaussian surface in the two cases.

(b) Let q be the charge inside the surface:

Question 21.
A conducting sphere of radius 10cm has an unknown charge. If the electric field 20cm from the centre of the sphere is 1.5 x 10³N/C and the points radially inward, what is the net change on the sphere?
Answer:
Consider a sphere of radius
R = (=10cm = 0.1 m) and centre O.
Let the charge on the sphere be ‘q’. Further, let ‘P’ be a point at a distance r = 20cm from the centre of the sphere.

The electric field E( = 1.510³NC^-1) is directed radially inward as shown. So as to enclose the charged sphere, draw a sphere (gaussian surface) with the point O as centre and r as the radius. As the electric field is radial, it is normal to the gaussian surface everywhere. Therefore, electric flux through the gaussian surface,

Question 22.
A uniformly charged conducting sphere of 2.4 m diameter has a surface charged density of 80 µ c/m²
(a) Find the charge on the sphere.
(b) What is the total electric flux leaving the surface of the sphere?
Answer:

Question 23.
An infinite line charge produces a field of 9 x 10⁴N/C at a distance of 2cm. Calculate the linear charge density.
Answer:

Question 24.
Two large thin metal plates are parallel and close to each other. On their inner faces, the plates have surface charge densities of opposite signs and of magnitude 17x 10^-22C/m². What is \(\vec { E } \)  :
(a) In the outer region of the first plate
(b) In the outer region of the second plate, and
(c) Between the plates?
Answer:
Here, σ= 17 x 10^-22 Cm^-2
(a) To the left of plates.
The electric field at this region is zero

(b) To the right of the plates
The electric field in this region is zero.

(c) Between the two plates
The electric field at this region is given by

2nd PUC Physics Electric Charges and Fields Additional Exercises

Question 25.
An oil drop of 12 excess electrons is hold stationery under a constant electric field of 2.55 x 10⁴ NC^-1 in is 1.26 g em^-3. Estimate the radius of the drop, (g = 9.81 ms^-2; e = 1.60×10 ¹⁹c)
Answer:

Question 26.
Which among the curves shown in Fig 1.35 cannot possibly represent electrostatic field lines?

Answer:
(a) It is not. Because field lines are not normal to the surfaces of the conductors.
(b) It is not, because, field lines cannot start from negative charge.
(c) It is correct representation of electric field lines.
(d) It is not because, field lines cannot intersect each other.
(q) It is not, because field lines cannot form closed loops without having touching the source or any charge.

Question 27.
In a certain region of space, electric field is along the z-direction throughout. The magnitude of the electric field is, however, not constant but increases uniformly along the positive z-direction, at the rate of 10⁵Nc¹ per meter. What are the force and torque experienced by a system having a total dipole moment equal to 10^-7cm in the negative z-direction?
Answer:
Suppose that a dipole consisting of charges – q at A and +q at B is placed along z-axis, such that it has dipole moment along the negative z-direction. The dipole moment of the dipole along z axis, P_Z= -10^-7Cm

The negative sign has been taken for they reason that dipole moment is along the x negative z-axis.

The electric field is applied along the positive direction of z-axis, such that (along z-axis) In a non – uniform electric field, the force on dipole is given by,

The negative sign shows that force on the dipole is along negative z-axis.
Since the elctric dipole moment is along negative z-axis and the electric field is along positive z-axis, 0 = 180°.
Hence, torque on the dipole, τ = pE sin 180° = 0.

Question 28.
(a) A conductor A with a cavity as shown in Fig. 1.36 (a) is given a charge Q. Show that the entire charge must appear on the outer surface of the conductor.
Answer:

(b) Another conductor B with charge q is inserted into the cavity keeping B insulated from A. Show that the total charge on the outside surface of A is Q + q [Fig. 1.36(b)].
(c) A sensitive instrument is to be shielded from the strong electrostatic fields in its environment. Suggest a possible way.
Answer:

Consider the gaussian surface (dotted) so as to enclose the cavity by lying wholly inside the conductor A. Since the electric field inside a conductor is zero, the part of the conductor within the cavity does not contain any net charge. By extending the same argument, no charge can be present inside the gaussian surface, which lies just within the conductor. Hence the entire charge A must appear on the outer surface of the conductor A.

consider the gaussian surface (dotted), it encloses the cavity and the conductor B with ^ charge q inserted in the cavity.

As such, the electric flux will cross the gaussion surface and it would imply that the electric field exists inside the conductor A. But the electric field inside the conductor A must be zero. It will be true, only if the charge q on conductor B induces charge-q on the inner surface and +q on the outer surface of the

Conductor A. As there is already a charge +Q on the outer surface of the conductor A, the total charge on its outer surface becomes Q+q.

(c) The electric field inside a metallic conductor is zero. Therefore, instrument can be shielded from the strong electrostatic fields by enclosing n it with a hollow metallic structure.

Question 29.
A hollow charged conductor has a tiny hole cut into its surfaces. Show that the electric field in the hole is \(\left( { \sigma }/{ { 2\epsilon }_{ 0 } } \right) \hat { i } \), where q is the unit vector in the outward normal direction and a is the surface charge density near the hole.
Answer:
Let \(\vec { E } \)be the electric field in the hole due to rest of the charged conductor. In order to find \(\vec { E } \) consider that the hole in the conductor is plugged. Let \(\vec { E } \) be the electric field due to the charged conductor at a point’ outside it then,

After plugging the hole, the conductor becomes a closed one, the electric field inside it must be zero. It implies that inside the conductor, electric field due to the rest of the conductor must be equal and opposite to that due to the small portion of the conductor, that plugs the hole. However, outside the conductor, the two fields are in the same direction i.e. along the outward normal to the surface of the conductor. It therefore, follows that the electric field in the hole due to the rest of the conductor,

Question 30.
Obtain the formula for the electric field due to a long thin wire of uniform linear charge density X, without using Gauss’ law
Answer:
Consider a long thin wire of uniform linear charge density λ  Let us find electric field due to the wire at the point P at a normal distance. PN = r from the wire Let AB = dx be a small elementary portion of the wire at a distance x from point N.

Then charge on the elementary portion AB, dq= λ dn

Therefore, electric field due to the small portion AB at the point P,

The component dE sin θdue to the different small portions, such as AB, will cancel each other. Therefore, effective electric field due to the small portion AB,

Question 31.
It is now believed that protons and neutrons are themselves built out of more elementary of charge \(+\frac { 2e }{ 3 } \) and then’ down quarks’ denoted by ‘d’ of charge \(-\frac { e }{ 3 } \) together with electrons build up ordinary matter. Suggest a possible quark composition of a proton and neutron.
Answer:
The charge on up quark (u) = \(+\frac { 2e }{ 3 } \)
The charge on down quark = \(-\frac { e }{ 3 } \)
The charge on proton is +e and it is made of three quarks. Therefore the possible quark composition of a proton is ‘uud

On the other hand, neutron is a neutral particle but it is also made of three quarks. For this, the possible composition of the neutron is ‘udd’.

Question 32.
(a) Consider an arbitrary electrostatic field configuration. A small test charge is placed at a null point of the configuration. Show that the equilibrium of the test charge is necessarily unstable.

(b) Verify the result for the simple configuration of two charges of the same magnitude and sign placed a certain distance apart.
Ans:
(a) To prove the result, let us assume that the test charge placed at the null point is in stable equilibrium. If it is so, then on being displaced slightly away from the null point, the test charge should return to its position., It implies that if a closed surface is drawn around the test charge, there will be a net inward flux of the electric field through its surface. According to Gauss law, there cannot be any electric flux through its surface as it does not enclose any charge. Hence our assumption is wrong and the test

(b) For the configuration of the two charges of the same magnitude and sign, the null point is the mid point of the line joining the two charges. If the test charge is displaced slightly from the null point along the line, it will return back due to the restoring force that comes into the day. But if the charge is displaced slightly from the null – point along normal to the line it will not return. This is because the resultant force due to the configuration of two charges will take it away from the null point. For the test charge to be in stable equilibrium restoring force must come into play, when it is displaced in any direction. Hence the test charge cannot be in stable equilibrium.

Question 33.
A particle of mass m and change -q enters the region between the two plates initially moving along X-axis with speed \({ V }_{ \lambda }\). The length The length of plate is L and a uniform electric field £ is maintained between the plates. Show that the vertical deflection of the particle at the far edge of the plate is \(-\frac { qE{ L }^{ 2 } }{ 2m{ v }_{ \lambda }^{ 2 } } \)
Answer:
Let y be the vertical deflection of the charged particle since the particle is initially moving along x-axis, its initial speed along the vertical.
The electric field E is directed along vertical. Therefore, acceleration of the particle along the vertical, \({ U }_{ y }=0\)
The time for which the force due to the electric field acts on the particle,
\({ a }_{ y }=\frac { qE }{ m } \)

Question 34.
Suppose that the particle in exercise 1.33 is an electron projected with velocity V_x = 2x 10⁶ms¹. If E between the plates separated by 0.5 cm is 9.1 x 10²Nc^_1, where will the electron strike the upper plate? Given, e = 1.6 x 10¹⁹C; and M_e = 1 x 10³¹ kg.
Answer:
Suppose that the electron strikes the upper plate at a distance x from the end, where it enters the electric field. Therefore the expression for vertical deflection becomes

2nd PUC Physics Electric Charges and Fields Additional Entrance Examination Questions and Answers

Question 1.
A charge Q is placed at each of the opposite corners of a square. A charge q is placed at each
of the other two corners. If the net electrical force on the Q is zero, then ~ equals
(A) -1
(B) 1
(C) \(-2\sqrt { 2 } \)
(D) \({ -1 }/{ \sqrt { 2 } }\)
Answer:
(C) \(-2\sqrt { 2 } \)

Question 2.
Four charge equals to -Q are placed at the four corners of a square and a charge q is at its centre. If the system is in equilibrium, the value of q is

Answer:
(A)

Question 3.
If the amounts of electric flux entering and leaving an enclosed surface respectively are \({ \phi }_{ 1 }\) and <\({ \phi }_{ 1 }\) the electric charge inside the surface will be

Answer:
(A)

Question 4.
A charged particle q is placed at the centre O of the cube (ABCDEFGH) of length L. Another same charge q is placed at a distance L from 0. Then, the electric flux through ABCD is.

Answer:
(C)

Question 5.
A thin spherical shell of radius R has charge Q spread uniformly over its surface. Which of the following graphs most closely represents the electric field E (r) produced by the shell in the range o≤ r < ∞ where r is the distance from the centre of the shell ?


Answer:
(B)

Question 6.
Two-point charge +8q and -2q are located at x = 0 and x = L respectively. The location of a point on z-axis at which the net electric field due to these two point charges is zero is (CET 2009)
(A) 2L
(B) L/4
(C) 8L
(D) 4L
Answer:
(D) 4L

Question 7.
If a charge q is placed at the centre of the line joining two equal charges Q such that the system is in equilibrium then the value of q is (CET 2010)
(A) Q/2
(B) -Q/2
(C) Q/4
(D) -Q/4.
Answer:
(D) -Q/4.

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Karnataka 2nd PUC Economics Question Bank Chapter 1 Introduction to Micro Economics

2nd PUC Economics Introduction to Micro Economics One Mark Questions and Answers

Question 1.
What do you mean by Economics?
Answer:
The term ‘Economics’ is derived from the Greek words ‘OIKOS” and “NOMOS which mean Household and management respectively. It studies the problem of choice at the individual social, national and international levels.

Question 2.
Define an economy.
Answer:
An economy is a mechanism through which the scarce resources are prioritized and organized for the production of goods and services. It also refers to a geographical-area where economic activities take place.

Question 3.
Why does an economic problem arise?
Answer:
An economic problem arises because of limited resources and unlimited wants and alternative uses of resources. While trying to allocate limited resources to satisfy unlimited wants, the problem of choice arises.

Question 4.
What is Planned economy?
Answer:
A Planned economy, also called as Socialistic economy is that economy where the economic activities are controlled by the central Government. Here, the Government takes decisions about the allocation of resources in accordance with objectives to attain economic and social welfare. Example, Russia, China, North Korea etc.

Question 5.
What is a Market economy?
Answer:
A Market economy also known as Capitalistic economy is that economy in which the economic decisions are undertaken on the basis of market mechanism by the private entrepreneurs It functions on demand and supply conditions. Example, USA.

Question 6.
What do you mean by mixed economy?
Answer:
A mixed economy is that economy in which we can see co-existence of both private and public sector enterprises. It is a combination of both Socialistic and Capitalistic features.

Question 7.
What is Positive economics?
Answer:
The Positive Economics is the study of ‘what was’ and ‘what is’ under the given set of circumstances. It deals with the scientific explanation of the working of the economy.

Question 8.
What is Normative Economics?
Answer:
The Normative Economics studies ‘what ought to be’. It explains about ‘what should be and should not be done’.

Question 9.
Define Micro Economics.
Answer:
Micro economics is the study of the economic actions of individuals and small groups of individuals. According to Boulding, “It is the study of particular firms, particular households, individual prices, wages, income, individual industries, particular commodities”.

Question 10.
Who first coined the terms ‘Micro’ and ‘Macro’ Economics?
Answer:
Prof.Ragner Frisch, the Nobel Prize winner in Economics (1920), coined the words Micro and Macro Economics for the first time.

Question 11.
Is the study of a sugar factory, a Micro-Economic study or a Macro-Economic study?
Answer:
The study of a Sugar factory is a Micro-Economic study.

Question 12.
What is Deductive Method of Economics?
Answer:
It is one of the methods of study of economics in which the conclusions are drawn from the general to the particular or from the universal to the individual.

2nd PUC Economics Introduction to Micro Economics Two Marks Questions and Answers

Question 1.
What is an economic problem and why does it arise?
Answer:
An economic problem is the problem of choice which arises because of limited resources and unlimited wants and the alternative uses of resources. The scarcity of resources is the main cause for this economic problem.

Question 2.
What are the basic functions of an economy?
Answer:
The basic functions of any economy are Production, Consumption, Distribution, Exchange, Economic planning and Social welfare.

Question 3.
Name the basic problems of an economy.
Answer:
The basic problems of an economy are What to produce, How to produce and for Whom to produce.

Question 4.
Name the types of economics.
Answer:
The types of economies are

1. Socialistic or Centrally planned Economy
2. Capitalistic or Market Economy and
3. Mixed Economy.

Question 5.
Give two examples of Centrally Planned economy.
Answer:
The Centrally planned or Socialistic economies are North Korea, Cuba, Russia, China and Vietnam.

Question 6.
Give two examples of a Capitalistic Economy.
Answer:
The examples for Capitalistic or Market Economy are USA, Japan, Australia, UK etc.

Question 7.
mention any two differences between Positive and Normative Economics.
Answer:

Positive Economics.	Normative Economics
The Positive Economics is the study of ‘what was’ and ‘what is’ under the given set of circumstances.	Here we study how the different mechanisms function.
It deals with the scientific explanation of the working of the economy.	Here we study how the different mechanisms function.
Here we study how the different mechanisms function.	Here we try to understand that whether the mechanisms are desirable or not.

Question 8.
Write any four practical importances of Micro-Economics.
Answer:

1. It helps in allocation of resources.
2. Provides solution to the problem of choice.
3. Helps in formulating various.economic policies.
4. Explains determination of the price.
5. Helps to know the working of an economy.

Question 9:
Mention any two limitations of Micro Economics.
Answer:

1. It has unrealistic assumptions.
2. It is based on unrealistic analysis.
3. Narrow in scope.

Question 10:
What is Inductive Method of Economics?
Answer:
It is the process of reasoning from a part to the whole, from particular to general or from individual to the universal.

2nd PUC Economics Introduction to Micro Economics Five Marks Questions and Answers

Question 1.
What is a centrally planned economy? How does it solve basic problems?
Answer:
A centrally planned economy also called as socialistic economy is that economy where the economic activities are controlled by the central Government. Here, the Government takes decisions about the allocation of resources in accordance with objectives to attain economic . and social welfare. Example, Russia, China, North Korea etc.

Here, the basic economic problems are solved as follows:
The Government takes decisions about the allocation of resources in accordance with the predetermined goals and objectives to attain maximum social welfare. Government decides what to produce, how to produce and what prices are to be fixed.

• Regarding what to produce, the Government may produce those goods and services which are most useful for its society.
• Regarding how to produce, the most suitable technique in production is adopted whether labour intensive or capital intensive in accordance with the situation in the economy.
• Regarding for whom to produce, the goods and services are produced to help those people who are suffering from hunger or shortage though there is a loss.
• It gives importance to the quality of life rather than quantity of production.
• It focuses the resources on rapid economic development.

Question 2:
Write a short note on Market Economy.
Answer:
A Market Economy also known as Capitalistic Economy is that economy in which the economic decisions are undertaken on the basis of market mechanism by the private entrepreneurs. It functions on demand and supply conditions. In USA, Japan, Australia, UK and other countries we can see Market Economic systems.

In market economy, private individuals own the factors of production. Here, profit is the sole motive. There is least intervention by the Government.

Price mechanism plays a major role in market economy. It is a balancing wheel of the market mechanism. Prices coordinate decisions of the producers and consumers. The price is determined by demand and supply in the market. No individual organization or Government is responsible for the production and distribution or pricing of goods. All depend on market mechanism).

Regarding the basic problems of an economy, the problem of “What to produce”, is solved on the basis of demand and profit. The producers produce those products which bring more income.

The problem of “How the goods are to be produced”, is determined by the competition among different entrepreneurs. They select the least cost combination of technology so that they can get more returns with less cost.

In Market Economy, the/problem of “For whom to produce”, is decided on the basis of purchasing power of consumers. The producers produce commodities for the rich as they can afford to pay more but poorer sections of the society get neglected.

In Market Economy, profits and losses play a predominant role in growth and development of every producer.

Question 3.
Explain the nature of Mixed Economy. How does it differ from Market Economy?
Answer:
A Mixed Economy is that economy in which we can see co-existence of both private and public sector enterprises. It is the combination of Socialistic and Capitalistic features. The best example for this is India.

In a Mixed Economic system, the resources are owned by both the Government and Private individuals. Here, some areas of economic activities are totally governed by the Government and other sectors are open to the private sector also.

The Government involves in those activities which promote maximum social and economic welfare without any profit motive. The Private sector functions with the intention of maximizing profits. Here we find dual pricing system. For example, the supply of Rice through Government Fair Price shojis is low when compared to the private provision stores.

In this type of economy, the Government takes the responsibility to run certain essential sectors like Railways, Printing of currency notes, Atomic energy, public parks etc. Here, the basic problems are solved both by Public and Private Sectors.

Regarding what to produce,-consumers play a main role. But, the Government also interferes by imposing tax or giving subsidy. The problem of how to produce, the private sector will follow the least cost effective technology to maximize profit and public sector will select , the technology on the basis of composition of resources. The problem of for whom to produce depends on both the purchasing power of consumers and the Government policy towards weaker sections of society.

Mixed Economy	Market Economy
(i) It is that economy where we can see both Public and Private Sector functioning.	(i)It is that economy where we can see only Private sector operating.
(ii)Price mechanism do not play much role	(ii)Price mechanism plays a major role.
(iii)It is a partially restricted economy	(iii)It is free economy
(iv)Both Private and Public Sector leads the economy.	(iv)Private sector leads the economy
(v)It is both profit motive and welfare motive.	(v)It is profit motive only

Question 4.
Is Economics Positive or Normative? Discuss.
Answer:
Positive Economics .

1. The positive economics is the study of ‘what was’ and ‘what is’ under the given set of circumstances. It is concerned with how the economy performs the basic functions of what to produce, how to produce and for whom to produce. It explains how the economy takes decisions about consumption, production and exchange of goods.

2. It deals with the scientific explanation of the working of the economy. It analyses every issue of economics from a positive perspective without passing any value judgments. It deals with the cause and effect relationship of economic variables.

Normative Economics:

1.The Normative economics studies ‘what ought to be’. It explains about ‘what should be and should not be done’. Here we try to understand that whether the mechanisms are desirable ornot. The normative economic statements are sometime called matters of op.nion or statements of value.

2. The advice given by various economists are mostly as per normative economics.
In India, Economic Advisers who are appointed by the Government are responsible for advising the Prime Minister as to which of the policies are good and beneficial to the country’s economy and which are bad and detrimental on the whole.

Economics is both Positive and Normative:

1. But, Economics is both a positive and normative science. The study of economics involves both scientific investigation and policy analysis. Economists first use science to explain the world and understand how the economy works, later policies are explored for the economic development.

Question 5.
What method would you prefer to formulate an economic theory?
Answer:
Economic theories are statements of economic tendencies of people. While developing economic theories, the Economists formulate assumptions. So, economic theory derives generalizations of economic facts through two methods: They are as follows:

Deductive Method: This method was developed by David Recardo, J.S.Mill, T.R.Malthus, Alfred Marshall and others. This method is also called as Analytical method.

under this method, the conclusions are drawn from the universal to the individual or from general to the particular. This method derives new conclusions from assumptions. It is also called as ‘Scientific Method’. It includes four stages viz.,

• Identification of the hypothesis to be tested.
• Generations of predictions from the hypothesis.
• Conducting experiments to check whether the predictions are correct.
• Confirming the hypothesis.

Inductive Method: This method was advocated by Frederic List, Rosher and Hilde Brand. Inductive method is a process of reasoning from particular to general or from individual to the universal. It functions in four stages viz.,

•  Selection of an economic problem and defining the same clearly.
• Collection of data using statistical techniques.
• Analysing the data.
• Observation and generalization to establish a general truth.

The inductive method is also called as historical method or concrete method and realistic method. In this method, we investigate particular facts or historical events and try to generalize the findings of the observation for the entire economic system.

It is concluded that both Deductive and inductive methods are e^ntial for the proper development of economic laws. According to Alfred Marshall, “Induction and deduction are both needed for scientific thought just as the right and left foot are both needed for walking”.

Question 6.
Explain the various limitations of Micro Economics.
Answer:
Micro Economics is the study of the economic actions of individuals and small groups of individuals. According to Boulding, “ It is the study of particular firms, particular households, individual prices, wages, income, individual industries, particular commodities”.
The major limitations of Micro Economics are as follows:

(a) Assumptions are unrealistic: The study of Micro-Economics assumes that ‘other tilings being constant’, which is not realistic. In fact, all factors are subject to change and not constant.

(b) Micro Economics is an unrealistic analysis: Micro-Economics uses static analysis. The conclusions drawn from Micro Economic analysis are not valid. For example, individual savings is good since it promotes individual economic prosperity. But if many people indulge in savings, it may lead to a fall in demand leading to less investment and causing unemployment.

(c) The assumption of full employment is incorrect: The microeconomics is based on the assumption of full employment i.e., all the resources are completely employed in production process, which is just imaginary and not correct.

(d) Laissez-faire policy (Minimum intervention of Government): The assumption of laissez faire policy is not practical in real world, where we see intervention of Government in economic activities.

(e) Ignores Macro economic analysis: The knowledge of an entire economy is very essential to the people as it includes all the economic elements. But the micro economics concentrates only on a small part of the whole economy.

(f) It is limited in scope: The scope of micro economics is limited and narrow. It does not include income theory, inflation, monetary policies etc. which are very important for economic analysis.

2nd PUC Economics Introduction to Micro Economics Ten Marks Questions and Answers

Question 1.
Discuss the basic problems of an economy.
Answer:
An economic system or economy is a mechanism where the scarce resources are channelized . on priority to produce goods and services. These goods and services produced by all the sectors of the economy determine the national income.

Generally, human wants are unlimited and resources to satisfy them are limited. If there was a perfect match between human wants and availability of resources there would have been no scarcity, no problem of choice and no economic problems at all. So, one has to select the most essential want to be satisfied with limited resources. In economics, this problem is called ’Problem of Choice’.

The problem of choice arising out of limited resources and unlimited wants is called economic problem. In every economy whether developed or underdeveloped, Capitalistic, Socialistic or Mixed economy, there will be three basic economic problems viz., What to produce, How to produce and For whom to produce. Let us discuss them in detail.

(a)What to Produce: Every country has to decide which goods are to be produced and in what quantities. Whether more guns should be produced or more foodgrains should be grown or whether more capital goods like machines, tools, etc., should be produced or more consumer goods (electrical goods, daily usable products etc.) will be produced. What goods to be produced and in what quantity depends on the economic system of.the country. In Socialistic economy, the Government decides and in Capitalistic economy market forces decide and in Mixed economy, both the Government and market forces provide solutions to this problem.

(b) How to Produce: There are various alternative techniques of producing a product. For example, cotton cloth can be produced with either handloom or power looms. Production of cloth with handloom requires more labour and production with power loom use of more machines and capital. It involves selection of technology to produce goods and services.

There are two types of techniques of production viz., (a) Labour intensive technology and (b) Capital intensive technology.
The society has to decide whether production be based on labour intensive or capital intensive techniques. Obviously, the choice of technology would depend on the availability of different factors of production (land, labour, capital) and their relative prices (rent, wages, interest).

(c) For whom to produce: Another important decision with economy has to take is for whom to produce. The economy cannot satisfy all wants of an the people. Therefore, it has to decide who should get how much of the total output of goods and services. The society has to decide about the shares of different groups of people- poor, middle class and the rich, in the national output.

Apart from above, an economy also faces other problems: they are as follows:

(a) The problem of economic efficiency: The efficient utilisation of existing resources of an economy has also become a major problem. The Optimum use of both natural and human resources is needed to prevent the wastage of these resources.

(b) The problem of full employment: Full employment means utilisation of resources to the fullest extent. Under utilisation of human resources leads to unemployment, disguised unemployment etc. If the natural resources are not used to the maximum, there is a wastage of potentiality of an economy.

(c) The problem of economic growth: Every nation wants to increase its Gross Domestic Product to achieve economic growth. This in turn improves the standard of living and reduces poverty and unemployment. Every economy has to increase its ability to produce more goods and services with the help of existing resources in order to achieve economic growth. But many developing countries are facing this problem of economic growth. So, the above are the basic problems of an economy common to all the economic systems of the world.

Question 2.
Explain the main types of Economic Systems.
Answer:
The main types of economic system are:

1. Socialistic/Centrally Planned Economy
2. Capitalistic/Market Economy and.
3. Mixed Economy.

1. Centrally Planned Economy or Socialistic Economy.
A planned economy also called as socialistic.economy is that economy where the economic activities are controlled by the central Government. Here, the Government takes decisions about the allocation of resources in accordance with objectives to attain economic and social welfare. Example, Russia, China,
North Korea etc. Here, the basic economic problems are solved as follows:

Government takes decisions about the allocation of resources in accordance with the predetermined goals and objectives to attain maximum social welfare. Government decides what to produce, how to produce and what prices are to be fixed.

• Regarding what to produce, the Government may produce those goods and services which are most useful for its society.
• Regarding how to produce, the most suitable technique in production is adopted whether labour intensive or capital intensive in accordance with the situation in the economy.
• Regarding for whom to produce, the goods and services are produced with the welfare of people who are suffering from hunger in mind even though there may be a loss.
• It gives importance to the quality of life rather than quantity of production.
• It focuses the resources on rapid economic development.

2. Market Economy:
A Market Economy also known as Capitalistic Economy is that economy in which the economic decisions are undertaken on the basis of market mechanism by the private entrepreneurs. It functions on demand and supply conditions. In USA, Japan, Australia, UK and other countries we can see Market Economic systems.

In Market Economy, private individuals own the factors of production. Here, the profit is the main goal of business. There is the least intervention of Government.

Price mechanism plays a major role in Market Economy. It is a balancing wheel of the market mechanism. Prices coordinate decisions of the producers and consumers. The price is determined by demand and supply in the market. No individual organization or Government is responsible for the production and distribution or pricing of goods. All depend on market mechanism.

Regarding basic problems of an economy, the problem of what to produce is solved on the basis of demand and profit. The producers produce those products which bring more income.

The problem of how the goods are to be produced is determined by the competition among different entrepreneurs. They select least cost effective combination of technologies so that they can get more returns for their investment.

In Market Economy, the problem of for whom to produce is decided on the basis of the purchasing power of the consumers. The producers produce commodities for the rich who can afford to pay more but poorer sections of the society are neglected.

In Market Economy, profits and losses play a predominant role in the growth and development of every producer.

3. Mixed Economy:
A mixed economy is that economy in which we can see co-existence of both private and public sector enterprises. It is the combination of Socialistic and Capitalistic features. The best example is India.

In a mixed economic system, the resources are owned by both the Government and Private individuals. Here, some areas of economic activities are totally governed by the Government and other sectors are open to the private sector.

The Government involves in those activities which promote maximum social and economic welfare without any profit motive. The Private sector functions with the intention of maximizing profits. Here we find dual pricing system. For example, the supply of rice through Government Fair Price shops is low when compared to the private provision stores.

In this type of economy, the Government takes the responsibility to run certain essential sectors like Railways, Printing of currency notes, Atomic energy, public parks etc. Here, the basic problems are solved both by Public and Private Sectors.

Regarding what to produce, consumers play the main role. But, the Government also interferes by imposing tax or giving subsidy. The problem of how to produce, the private sector will decide the best cost effective technology to maximize profits and public sector will select the technology on the basis of composition of resources. The problem of for whom to produce depends on both the purchasing’power of the consumers and the Government policy towards weaker sections of the society.

Question 3.
Explain the uses of Micro-Economics.
Answer:
Micro Economics is the study of the economic actions of individuals and small groups of . individuals. According to Boulding, “The study of particular firm, particular household, individual price, wage, income, individual industry, particular commodity, is Micro Economics.”

Micro Economics is an important method of economic analysis. It has both theoretical and practical importance.

(a) Helpful in the efficient employment of resources-allocation of resources: Micro Economics deals with the economizing of scarce resources with efficiency. The principal problem faced by modern Governments is the allocation of resources among competing wants. In this sense, Micro Economics is used by the Government in the efficient employment of resources and achieving economic growth With stability.

(b) Helps in understanding the working of the economy: Micro Economics is of utmost importance in understanding the working of a free economy. In such an economy, there is no agency to plan and coordinate the working of the economic system. The decisions like how to produce, what do produce etc., are taken by producers mid consumers without any outside influence.

(c) Provide tools for economic policies: Micro economics provides analytical tools for evaluating the economic policies of an Economy. Price mechanism or market mechanism is the tool which helps us in this respect. Micro Economics thus helps in formulating correct price policies.

(d) Useful in understanding the problems of Taxation: The study of micro economics helps in understanding some of the problems of taxation. It is used to explain the welfare implications of a tax. It studies the distribution of incidence of a commodity tax (excise duty/sales tax) between sellers and consumers.

(e) Helpful in International Trade: In the field of international trade, it is used to explain the gains from international trade, balance of payments and the determination of the foreign exchange rate.

(f) Helps us to know Market structure: The study of Micro Economics is useful in understanding the different market conditions like perfect competitive market, monopoly, duopoly, oligopoly etc.

(g) Construction and use of economic models: Micro Economics constructs and uses simple models for understanding the actual economic phenomena. It helps not only to describe the actual economic situation, but also suggests policies that would bring in the desired results;

(h) The basis of predictions: Micro Economic theory can be used as the basis for prediction. This does not mean that it will enable us to predict the future. It will enable the user to make conditional predictions.

(i) Solution to the problem of choice: The study of Micro Economics helps to find solution to the problem of choice by providing various guidelines for proper allocation of scarce
resources.

(j) Helps business executives: Micro Economics helps the business executives in the attainment of maximum productivity with existing resources. It is with its help that one is able to know the consumer demands and calculate the cost of production.

(k) Helps in formulation of economic planning: In order to solve the basic problems of an economy, conscious planning is required. The knowledge of micro economics helps the members of National Planning Commission to frame aims and objectives based on the availability of resources.

(l) Expands intellectual capacity of Human mind:- The study of economics helps individuals to develop their thinking and intelligence to take appropriate decisions in their daily life.

(m) To examine the conditions of economic welfare: Micro Economics can be used to examine the conditions of economic welfare. Welfare economics is related to maximization of social welfare. The study of Micro Economics may be the greatest help in raising the standard of living of the population.

(n) Helps different sections of the society: The knowledge of Micro Economics is very important to know the different sections of the society like poor, middle class, rich, male and female population, skilled and unskilled labourers etc. It helps us to understand the problems of these sections and to arrive at proper Solutions.
Thus, Micro Economics is considered as an efficient method of problem solving.

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2nd PUC Biology Environmental Issues NCERT Text Book Questions and Answers

Question 1.
What are the various constituents of domestic sewage? Discuss the effects of sewage discharge on a river.
Answer:
Domestic waste – Waste that is produced from our homes and passed down into sewer system matter that floats . Effects of sewage on river.

Quality of water is decreased . So it becomes unsuitable for bathing, domestic uses etc.,

B.O.D- [Biological oxygen demand] – More waste in water, more decomposers come into action, much larger amount of O₂ utilized so, B.O.D. increases and dissolved oxygen becomes less.

Question 2.
List all the wastes that you generate, at home, school or during your trips to other places, which you could easily reduce? Which would be difficult or rather impossible to reduce?
Answer:

• At home – Kitchen wastes, food-left overs, old torn clothes, papers, carry bags, cotton, broken articles (glass, crockery), leather, plastic, cans etc.,
• At school – Pencil, pencil peels, rubbers, pens, chalk, paper, food, grit etc.,
• At trips – Food, carry bags, food wrappers, water bottles, cups, spoons, plate, faeces and urination in open air.
• Wastes which can be reduced – Biodegradable wastes e.g. papers, rags, food, leather articles, others which are recyclable ones in house or locality itself.
• Which cannot be reduced – Glass, tin, metals, plastics, polythene. They are recycled and reused. Also as land fills. So non biodegradable are to be sold to ragpickers.

Question 3.
Discuss the causes and effects of global warming. What measures need to be taken to control global warming?
Answer:

• Global warming is rise in mean temperature of lower atmosphere and earth’s surface.Causes – increase in quantity of radioactively active green house gases CO₂, CH₄, N₂O, CFCs. They allow heat waves to reach surface and prevents their escape.
• They are produced by combustion of fossil fuels, biomass [CO₂]; burning of nitrogen rich fuels [N₂O]; paddy fields, fermentation in cattle and wet lands [CH₄]; refrigerators, aerosols, drying, cleaning [CFCs].
• Effects: Heating of earth surface [mean temperature is increased] Climatic changes e.g.: El Nino effect.
• Increased melting of polar ice caps and Himalayan snow caps. Increased sea levels and coastal areas will submerge.
• Measures – Decreased use of fossil fuels, improve efficiency of energy usage, Reduce deforestation, plant trees Control of man made sources of green house gases like vehicles, aerosol sprays.

Question 4.
Match the items given in column A and B:

Column A Column B
(a) Catalytic converter – (i) Particulate matter
(b) Electrostatic – (ii) Carbon precipitator monoxide and nitrogen oxides
(c) Earmuffs – (iii) High noise level
(d) Landfills – (iv) Solid wastes
Answer:
(a) Catalytic converter – (i) Co & NO
(b) Electrostatic – precipitator (ii) Particulate matter
(c) Earmuffs – (iii) High noise level
(d) Landfills – (iv) Solid wastes

Question 5.
Write critical notes on the following:
(a) Eutrophication
(b) Biological magnification
(c) Groundwater depletion and ways for its replenishment.
Answer:
(a) Eutrophication :-
Natural aging process of lakes by nutrient enrichment of its water. In young lake water is cold and clear and supports only little life. With time, streams introduce nutrients into lake which increases lakes fertility and encourages aquatic growth. Over centuries silts and organic debris pile up, and lake becomes shallow and warmer. It supports plants and later gets converted into land. Lakes span depends on climate, size of lake.

(b) Biological magnification: Bio magnification is due to introduction of toxic substances from industrial and household waste into aquatic food chain. Concentration of toxic substance accumulated by organism increases at each trophic level – Bio magnification, eg: Toxic substances like mercury, DDT, etc.
They later lead to entrophication.

Birds (25 ppm)
↑
large fish (2ppm)
↑
small fish (0.5 ppm)
↑
zooplankton (0.04 ppm)
↑
water (0.003 ppm)
(DDT concentration showing bio magnificarion)

(c) Groundwater depletion and ways for its replenishment
Groundwater depletion – due to high demand of water in urban, hilly, arid areas where surface water is not available or polluted, ground water is the major source of water drawn using tube wells, pumps etc., [in Punjab, T.N, Rajasthan]

Replenishment –

• Reduced consumption or stop using groundwater for irrigation and cleaning etc.
• Rainwater harvesting – Collection of rainwater and diverting them into ground using pipes or into rivers or rainwater tanks. [As alternate source of water also].

Question 6.
Why ozone hole forms over Antarctica? How will enhanced ultraviolet radiation affect us?
Answer:
Ozone hole forms over Antarctica where no one lives and no pollution is present but not over Newyork, Bangalore etc., (polluted cities). It is because CFCs and ozone depleting substances (ODS) released world wide accumulates in stratosphere and drifts towards, Antartica in winters (July – August) when temperatures is -’85° C in Antartica.

In winters polar ice clouds are formed over Antartica. It provides catalytic surface for (CFCs and other ODS to release CL and other free radicals that breakdown ozone layer forming ozone hole during spring in presence of sunlight. In summer, ozone hole disappears due to mixing of air world wide.

Ozone holes allows UV radiations (UV_A & UV_B) to reach earth surface. Which was earlier reflected by ozone layer. UV_B damages DNA, skin cells and causes mutations and skin cancer’s respectively. UV_B even causes corneal damage (Snow Blindness).

Question 7.
Discuss the role of women and Communities in protection and conservation of forests.
Answer:
(i) Bishnois – are group of followers of Guru Janbeshwar Maharaj, a small community inhabiting a village near Jodhpur in Rajasthan. They are known for peaceful co-existence with nature. In 1731, once when king of Jodhpur, asked his fellow people to arrange wood for new palace, they reached Bishnois village. Effort of cutting trees was thwarted by Bishnois. A Bishnois women Amrita Devi hugged the trees and daring King’s men to cut her before cutting the trees. But, kings men cut the tree down along with her. Her 3 daughters and 100 other Bishnois followed her and all lost their lives saving trees. Now there is Amrita Devi Bishnoi Wildlife Protection Award given to individuals or communities from rural area who show courage and dedication to protect wildlife and trees.

(ii) Chipko movement – of Garhwal Himalayas. In 1974, local women showed extreme courage by hugging trees and protecting them from the axe of contractors.

(iii) Appiko movement – Conservation, plantation and Rational use is their belief.
(iv) Joint Forest Management (JFM) – Government of India in 1980s introduced concept of JFM so as to work closely with local communities for protecting and managing forests. In return their service, they were rewarded with various benefits and forest were conserved in. sustainable manner. Communities got benefit of various forest products like fruits, gum, rubber, medicine etc.

Question 8.
What measures, as an individual, you would take to reduce environmental pollution?
Answer:

• No biomass burning and minimal use of fossil fuels.
• Vehicles – use of minimum pollution vehicles fitted with catalytic converters.
• Smoking – No tobacco smoking and implementation of Kitchen chimneys
• Noise – Not using TV and other gadgets at louder pitch.
• Tree plantation -1 will plant trees around school, house and also in other places.
• Wastes -1 will dispose of waste property after segregation.

Question 9.
Discuss briefly the following:
(a) Radioactive wastes
(b) Defunct ships and e-wastes
(c) Municipal solid wastes
Answer:
Radioactive wastes – Nuclear energy
(source of non-polluting electricity) has 2 important problems

• Accidental leakage (Chernobyl incident);
• safe disposal is a problem for radioactive waste.

Radiations are extremely damaging to organisms, because of its mutations at very high rate. At high doses, it is lethal but at lower doses, creates various disorders like cancer, anomaly, etc. Their disposal is also a serious issue. Low level and intermediate level wastes do not produce – heat and other environment problems, so are safe dumping in process inside proper containers. But high level wastes which release lots of heat and cause environmental problems are put in suitable containers and buried 500 m deep inside rocks inside the earth.

(b) Defunct ships and e-wastes. Defunct ships – old ships are dismantled to obtain scrap and other useful materials mainly in developing countries , due to less labour charge and low tax. Workers engage in ship breaking are exposed to number of toxicants like asbestos, lead, mercury etc. Coastal area associated with ship breaking yard in also polluted.

e-wastes (electronic wastes) – They are increasing due to increase use of e – equipments and rapidly changing technologies. From it metals (copper, iron, silicon, nickel, gold) etc. are extracted. Dismantling also exposes them to toxic substances.

(c) Municipal solid wastes – Domestic waste office wastes, school, public sweeping, sludge from sewage treatment plants, vegetables, fruit markets. They may be bio-degradable or non¬bio-degradable. They consists of paper (40%), food waste (7%), glass, crockery, rubber,- leather, plastics etc. Their disposal is mainly done by: Pig and cattle feeding, salvage, Burning, incineration, land fills, pyrolysis (heat), composting, Biogas plants, Recycling etc.

Question 10.
What initiatives were Jtaken for reducing vehicular air pollution in Delhi? Has air quality improved in Delhi?
Answer:
Initiatives taken were:
A PIL (Public Interest Litigation) was filed before supreme court of India. Supreme court undertook time bound measures for reducing pollution by switching over to CNG is public transport, enforcement of Eura II norms, periodic pollution checkup, use of unleaded petrol, catalytic converters in vehicles and phasing out old vehicles. Air quality has improved significantly. A substantial fall in CO₂ and SO₂ has been found in Delhi between 1997 and 2005.

Question 11.
Discuss briefly the following :
(a) Greenhouse gases
(b) Catalytic converter
(c) Ultraviolet B
Question
Answer:
Green house gases – are those gases which allow short wave radiations to pass through but absorb long wave heat radiations: eg: CO₂, CH₂, N₂O, CFCs.
They cause green house effect and increases surface temperature making earth. Sustainable or life

Question Downward flux of long waves by green house gases is called green house reflux. It keep earth warm at 15°C, without it earths temperature would dropto-18°C.

But enhanced green house effect causes globalwarning that is leading to deleterious changes in environment and resulting in odd climate changes.

(b) Catalytic Converter : It is a method to reduce emissions from automobiles. The device has a platinum – palladium and Rhodium as catalyst. Exhaust emissions passes through it; nitric oxide splits into nitrogen and oxygen, Carbon monoxide into carbon dioxide, unburned hydrocarbons get burned to form CO₂ and H₂O. It is useful only is unleaded petrol because lead inactivates catalyst of the convertor.

(c) Ultraviolet B (UVB) – They normally do not reach earth surface as ozone layer reflects it back. But due to ozone hole, UVB reaches earth surface these days.
They cause:

• Skin cancer
• Blinding – Corneal damage .
• Immune system is partially suppressed
• Larval stages die
• Photosynthesis – is impaired so crop yield falls.
• Nucleic acids – Mutations
• Phytoplankton – their function is disturbed so productivity falls.
• Global warning.

2nd PUC Biology Environmental Issues Additional Questions and Answers

2nd PUC Biology Environmental Issues One Mark Questions

Question 1.
Name any 3 gases contributing to green house effect. (CBSE 2004)
Answer:
CO₂, methane (CH₄), Nitrous oxide (N₂O).

Question 2.
Which type of UV-radiations can be lethal to organisms. (CBSE 2005)
Answer:
The most harmful UV-radiation is UV- C have a range of 100-280 nm. They are absorbed by oxygen molecules of atmosphere. The next goes to UV-B with a range of 280-32 nm wavelength.

Question 3.
What are ODS. Give examples. (CBSE 2005)
Answer:
Certain substances react with ozone present in the stratosphere and destroy the ozone. They are called ozone depleting substances or ODS. The majors ODS are CFCs, halons (gases used in fire extinguisher i. e. like bromo chloride fluoro methane), N₂O, CH4, Cl etc.

Question 4.
What is ozone shield or ozone layer?
Answer:
The region in stratosphere where ozone is present in high concentration is called ozonosphere or ozone layer or ozone shield.

Question 5.
What is ozone hole?
Answer:
The thinning of ozonal layer over the Antarctic region is called ozone hole.

Question 6.
What is acid rain.
Answer:
It is the deposition of acidic chemicals of atmosphere over the earth by combining with rain droplets.

Question 7.
What constitute smog.
Answer:
It is opaque dark fog which is formed by smoke, dust, oxides of sulphur, nitrogen, H₂S, water vapour etc.

Question 8.
Expand the term PAN and BOD, PPN. (CBSE 2005, 2007, 2008)
Answer:

• PAN – Peroxy acyl nitrate
• BOD – Biological oxygen demand
• PPN – Peroxy – propional nitrate.

Question 9.
Many villagers near Industrial are a sufferer from “blue baby syndrome! How is this problem caused. (CBSE 2004)
Answer:
From the industries, nitrate containing impurities add to the water causes water pollution. When these people drink this water, nitrite changes into nitrate and passes into blood and oxidises ferrous of haemoglobin to ferric ion. This way formed hemoglobin is called methemoglobin. This reduces, oxygen carrying capacity of blood. This results in cyanosis in infants called blue baby syndrome.

Question 10.
What is Sonic Boom?
Answer:
It is a series of shock waves left behind by a supersonic Jet flying at a speed. It produced sudden rattling of windows and doors. Building many develop cracks.

Question 11.
Define biomagnification.
Answer:
It is the increase in the concentration of certain toxic chemicals like DDT at successive trophic levels through food chain is called biomagnfication.

Question 12.
What do you mean by entrophication?
Answer:
It is defined as the nutrient enrichment in the water bodies leading to the depletion of oxygen and deadening of the life supporting environment, due to slow ageing of water bodies.

Question 13.
What is meant by algal bloom?
Ans:
The excessive growth of certain phyto planktons, facilitated by the excess presence of nutrients in the water bodies is called algal bloom.

Question 14.
Name the world’s most problematic aquatic weed? What is the nature of water body in which this weed grow? (CBSE 2008)
Answer:
Eichhomia crassipes is the problematic aquatic weed grow in eutrophied water body.

Question 15.
Expand CPCB..
Answer:
Central Pollution Control Board.

Question 16.
Define Pollutants.
Answer:
Those agents which bring undesirable change in the physical chemical and biological characteristics of air, water and soil are called pollutants.

Question 17.
Write the main aim of Environment Act in 1986 (pollution).
Answer:
“Protect and improve the quality of our environment i.e. air, water and soil”.

Question 18.
What is meant by green house effect?
Answer:
Green house effect is a naturally occurring phenomenon, in which the short wave radiations of solar energy are absorbed and long wave radiations are reflected by the earth, but reabsorbed by certain gases and increases the, temperature of earth’s surface and atmosphere.

Question 19.
Between amphibians and birds, which will be able to cope with global warming? Give reason.
Answer:
Birds. Because they are warm blooded animal can adjust the body temperatures as per the changes in the environment.

Question 20.
What gases cause stratospheric ozone depletion? What is the result of this depletion? (CBSE 2004)
Answer:
N₂O, CH₄, CO₂, chlorine are some of the gases lead to the ozone depletion. The depletion leads to the ozone hole which allows the entry of UV-B radiation to the earth surface. This radiation causes skin cancer, blindness, global warming etc.

Question 21.
What will be the consequences if the electrostatic precipitator of a thermal power plant fails to function?
Answer:
In the absence of electrostatic precipitator the particulate pollulants and gaseous pollutants of the exhaust will get into the atmosphere.

Question 22.
What is Snow blindness.
Answer:
Snow blindness is the inflammation of cornea caused by a high dose of UV-B radiations.

Question 23.
Where did the Chipko movement start?
Answer:
In Garhwal Himalayas.

Question 24.
What is Chipko movement?
Answer:
The movement led by Gaura Devi along with Sunder Lai Bahuguna of Tehri region of Uttara Khand to prevent felling of trees by hugging the trees.

Question 25.
What JFM. What is its main objectives.
Answer:

• Joint Forest Management.
• Protection of Sal forest by local communities.

Question 26.
What ITS the main objective of Montreal Protocol?
Answer:
Limiting production and consumption of chlorofluro carbon to half the level.

2nd PUC Biology Environmental Issues Two Marks Questions

Question 1.
What are major causes of soil erosion?
Answer:

• Over Cultivation
• Poor irrigation practices
• Deforestation
• Unrestricted grazing.

Question 2.
What is Montreal Protocol? What is its aim?
Answer:
Montreal Protocol is an international treaty, that was signed at Montreal (Canada) in 1987 and become effective in 1989. The main .aim is to control the emission of a ozone depleting substances.

Question 3.
Waterlogging can increase the soil salinity. Discuss.
Answer:
Waterlogging draws salt to the surface of the soil. This salt is then deposited as a thin crust on the land surface and starts collecting roots of the plant.

Question 4.
Mention the harms caused by fine particulates in human.
Answer:

• They may be inhaled deep into the – lungs and cause breathing and respiratory problems.
• Irritation of lungs.
• Inflammation of lungs.
• Premature death.

Question 5.
How is letting of sewage into water bodies cause fish mortality?
Answer:

• As the sewage is discharged into water bodies, there is an increase in the biodegradable organic matter.
• The micro organisms multiply fast with the increase in organic matter, which Is used as its substrate for them.
• These microbes consume a lot of oxygen and there is a sharp decline in the dissolved oxygen content of the water body, this leads to fish mortality.

Question 6.
Differentiate between Biodegradable and non biodegradable waste.
Answer:

• Biodegradable: These are the waste which can be broken down into simpler harmless substances by the activity of decomposers. These substance are used as manures.
• Non-biodegradable: The substances which cannot be broken down into simpler substances by microbes and they start accumulating in the biosphere.
  This causes pollution and can lead to biomagnification.

Question 7.
Write an account on Ecosan -Ecological sanitation.
Answer:

• Ecological sanitation is a subtainable system for handling human excreta, using dry composition toilets.
• This is a practical, hygienic, efficient and cost effective solution to human waste disposal.
• In this method, human excreta an be recycled into manures that reduce the need for chemical fertilizers.
• There are working ecosans in Kerala and Srilanka.

Question 8.
How is organic farming advantageous?
Answer:

• This allows maximum utilization of resources.
• It increases the efficiency of production.
• There is no need for chemical fertilizers for crops, as cattle excreta, can be used as manures.
• Crop wastes are also decomposed and used as manures.
• Cattle dung and crop wastes are used to generate biogas, that is used for cooking and lighting.

Question 9.
How is the green house effect caused?
Answer:

• The atmospheric gases absorb half of the incoming solar radiations and heat the earth surface.
• Earth surface re-emits the heat in the form of infra red radiation.
  A large part of this is absorbed by the green house gases (CO₂, CH₄, N₂O, CFCs etc).
• The molecule of these gases radiate heat energy back into the atmosphere and the earth’s surface is heated up once again.
• This cycle is repeated a number of times and there is an increase in the global temperature.

Question 10.
Differentiate between “Good ozone” and “Bad ozone”.
Answer:

Good ozone	Good ozone
Good ozone refers to the ozone found in the stratosphers.	Bad ozone refers to the ozone found in the troposphere.
It absorbs UV radiations and protects the living organisms of the earth.	This is harmful to plants and animals.

Question 11.
Mention any 3 reasons for deforestation.
Answer:
Deforestation is caused due to human activation for following purposes.

• Forests are cleared for making homes and industries due to over population.
• Forests are converted into agricultural land to produce food for increasing population.
• Trees are fell for timber, firewood and other uses.

Question 12.
Thermal power plants are necessary to any country, but they cause harm to the environment and community. Mention how they are harmful to the environments and people. What precaution can be taken to avoid this effect?
Answer:

• Thermal power plants release both particulate and gaseous air pollutants from their smoke stakes.
• When they are inhaled, it cause breathing respiratory disorders, irritation and inflammation of lungs leading to premature death.
  Precausion
• By installing an electrostatic precipitator, more than 99% of the particulate matter will be absorbed.
• Scrubbers can be used to remove gaseous pollutants.

Question 13.
“Eutrophication can lead to the death of a lake” Discuss.
Answer:

• The main pollutants in sewage, industrial wastes and agricultural run off are nitrates and phosphorus.
• These pollutants stimulates the growth of algae which leads to the depletion of oxygen in water bodies, causes the death of aquatic organisms.
• Other toxic substances flowing into the lake can kill all the fishes and other animals in the water.
• Due to the decomposition of these bodies the oxygen level further decreases in the water body
• Ultimately this leads to the death of the lake.

Question 14.
What does BOD indicate? What is its relationship with the dissolved oxygen content of the water body?
Answer:
BOD is Bio logical oxygen demand which is measure of the oxygen required by aerobic decomposers for the degradation of biodegradable organic matters in the water bodies.
If BOD is higher, it indicates the high level of organic matter and viceversa.

2nd PUC Biology Environmental Issues Three Marks Questions

Question 1.
Mention the harmful effects of noise on human health.
Answer:

• Sleeplessness and headache
• Noise level of 150 dB or more than these can cause permanent hearing impairment
• Increased heart beating and blood pressure
• Difficultly in breathing
• Strees and strain

Question 2.
Describe the particular type of agriculture practised in north eastern states of India which has also contributed to deforestation. What is it commonly called as?
Answer:
Slash and Burn agriculture is practised in north-eastern states of India.
In this method the farmers cut down the trees of the forest and burn them and clear a certain area for farming.

The ash is used as manure and the land is used for cultivation of crops or grasses for cattle grazing. ‘After cultivation for a period of time, the land is left free for several years to allow its recovery The farmers move to a different areas in the forest and this process is repeated. This practise is commonly called as Jhum Cultivation.

Question 3.
What is meant by ozone hole? When does it develop every year? How are CFC’s responsible for this?
Answer:
Ozone hole is the thinning of ozone layer is stratosphere and it is marked over the Antartica region. It develops every year late August and early October.

In the stratosphere the VU rays act on the CFCs and release chlorine atoms. There chlorine atoms degrade the ozone layer by acting as a catalyst. Since the chlorine atom are not consumed in the reaction the CFCs have a permanent and continuing effect on ozone holes.

Question 4.
The figure given aside shows relative contributions of various green house gases to the total global warming.

Answer:
(i) Name the gases a and b.
(ii) Explain how increase in green house gases in earth’s atmosphere leads to melting of the caps.
Answer:
(i) (a) N₂O
(b) CH₄
(ii) Increase in green house gases (GHGs) results in increased green house flux or trapping long wave radiations and sending them back to earth. It increases atmospheric temperature called global warming. High atmospheric temperature results in melting of ice caps and glaciers.

Question 5.

The above diagram shows simplified biogeochemical cycle.
(a) Name the compound whose cycle is deposited
(b) In what way do vehicles add this compound to the atmosphere?
(c) What adverse effect does it excess have on the environment?
(d) Cite an event which depicts this effect in modern times.
(e) Suggest 2 ways of reducing this effect.
Answer:
(a) CO₂ cycle
(b) By burning fossil fuel
(c) Global Warming
(d) Melting of glaciers and slow rise in sea level, submerging of low lying islands.
(e)

• Limiting the use of fossil fuels
• Increase the vegetation cover

Question 6.

Study the graph and answer the following questions
(1) What is the relationship between dissolved oxygen and biochemical oxygen demand (BOD)
(2) Mention their effect on aquatic life of the river.
Answer:

1. The dissolved oxygen content is inversely proportional to BOD i.e. when BOD rises, the content of dissolved oxygen decreases and vice versa.
2. When BOD is high, the aerobic aquatic organism will die due to decreased availability of disolved oxygen. When BOD is low, the content of dissolved oxygen becomes high. In clear water, aerobic aquatic organisms reappear.

2nd PUC Biology Environmental Issues Five Marks Questions

Question 1.
Differentiate between Biological magnification and eutrophication. (CBSE2007)
Answer:

Biological Magnification	Eutrophication
(a) It is increasing concentration of a persistent pollutant With the rise in trophic level.	It is nutrient enrichment of a water body.
(b) It occurs both in terrestial and aquatic ecosystem	Occurs only in aquatic ecosystem
(c) There is no excessive growth	There is excessive growth of algae
(d) Organic loading is absent	Organic loading occurs in water body.
(e) The higher order consumers are harmed most.	The whole aquatic ecosystem is damaged.

Question 2.
Given below are the sources of pollution and their effects. Using this information, fill the spaces in the given box. Each pollutant may have more than one source and may show more than one effect. Pollutant source: Automobile exhaust, Burning of fossil fuels, refrigerant, agricultural field, lire extinguisher, paint solvents, Deforestation, plastic foam.
Effect: Photo-chemical smog, Acid deposition, global warming, Depletion of ozone.
Answer:

Name of pollutant	Source	Effect
CFC Suspended particulate matter (SPM) Oxides of nitrogen Sulphur dioxide Methane (CH4)

Answer:

• CFC: Sources – Refrigerant, Fire extinguisher, paint solvents, plastic foam.
  Effects: Depletion of ozone, global warming
• SPM: Sources – Automobile exhaust, Burning of fossil fuel
  Effect: Photochemical smog.
• Oxides: Source-Automobile exhaust, Burning of nitrogen of fossil fuel, Agricultural field.
  Effect: Photochemical smog, Acid-deposition, global warming.
• Sulphur dioxide: Source – Automobile exhaust, Burning of fossil fuel.
  Effect: Acid deposition.
• Methane Sources: Agricultural field, Burning of fossil fuel.
  Effect: global warming.

Question 3.
Differentiate between
(a) BOD and COD
(b) Montreal and Kyoto protocols.
Answer:
(a) BOD and COD

BOD	COD
(i) It is biochemical oxygen demand	It is chemical oxygen demand.
(ii) Its value is lower	Its value is higher
(iii) It measures oxygen demand for the completion of degradation of organic matter.	It measures oxygen demand for oxidising all the red­uced substances, whether organic or inorganic.
(iv) It employes decompose microbes	It employs potassium permanganate or potassium diehromate.

(b) Montreal and Kyoto protocols.

Montreal Protocol	Kyoto protocols
(i) It is related to a reduction  in the production and consumption of CFC and other ODS.	It is related to emission of CO2 and other greenhouse gases
(ii) The protocol was signed in 1987	(ii) This was signed in 1997
(iii) It was followed by Helsinki decla­ration to phase out CFCs and halons. The road map was prepared to help the actions to replace CFC and ODS.	(iii) It has been followed by Bati conference in 2007 Road map has been prepared to reduce emission of green house gases by 2012.

(a) What is meant by deforestation? Mention the cause of it.
(b) Why is CNG preferred to diesel/petrol
Answer:
It is the conversion of forest areas to non forest areas and ultimately to a desert.
(a) Causes of deforestation are

• Conversions of forest land to agricultural land to produce food for* increasing population.
• Cutting of trees for timber and wood
• Jhumcultivation in the north-eastern states of India
• Forest fires.

(b)

• CNG burns most efficiently in the automobiles and leaves very little of it unburnt.
• CNG cannot be adulterated like petrol/diesel
• It cannot be siphoned by thieves
• It is cheaper than petrol/diesel.

Question 5.
Why do you consider that integrated organic farming is more advantageous?
Answer:
Integrated organic farming is a cyilical, zero-waste process, in which the waste materials from one process are used as nutrients or raw materials for the other process. The resources are utilized to the maximum and the efficiency of production is increased. Since the process support one another, it is an extremely economical and sustainable procedure. There is no need to depend on chemical fertilizers and pesticides as cattle dung is used as manure. Crop residues are decomposed and they are used as manure.
Dung of animals and crop residues are used to produce biogas, which satisfies the energy needs of the farm.

You can Download Chapter 15 Biodiversity and Conservation Questions and Answers, 2nd PUC Biology Question Bank with Answers, Karnataka State Board Solutions help you to revise complete Syllabus and score more marks in your examinations.

Karnataka 2nd PUC Biology Question Bank Chapter 15 Biodiversity and Conservation

2nd PUC Biology Biodiversity and Conservation NCERT Text Book Questions and Answers

Question 1.
Name the three important components of biodiversity.
Answer:
(i) Genetic biodiversity
(ii) Species diversity
(iii) Ecological diversity

Question 2.
How do ecologists estimate the total number of species present in the world?
Answer:
Total number of species is estimated by:

• Rate of discovery of new species
• Determination of species richness is an area.

Question 3.
Give three hypotheses for explaining why tropics show greatest levels of species richness.
Answer:
In tropics:-

• No Catastrophes – In tropics, there has been no catastrophes but is temperate areas glaciations and other catastrophes have caused large scale of destruction.
• Non-seasonal Environment – In tropics, seasons are nearly uniform. It promotes rich and increases species diversity.
• Solar Energy – Tropics get lots of sunlight which enhances productivity.

Question 4.
What is the significance of the slope of regression in a species-area relationship?
Answer:
Slope of regression/regression co-efficient of species-area relationship indicates that species richness decreases with decrease in area.

• Regression coefficient is between 0.1 – 0.2 regardless of taxonomic group or region, eg: Plants in Britain, Birds is California.
• But in large areas like continents value is eg:- Frugivorous birds, mammals is tropical forests.

Question 5.
What are the major causes of species losses in a geographical region?
Answer:
Habits loss, Hunting, Habital fragmentation, Forest fires. Alien species, Co extinction, Pollutions/Disturbance, Intensive agriculture, etc.

Question 6.
How is biodiversity important for ecosystem functioning?
Answer:

• Biodiversity is important for productivity, stability, resilience and health of ecosystems.
• Biodiversity is important not only for ecosystem function but also for very survival of human race on earth.

Question 7.
What are sacred groves? What is their role in conservation?
Answer:

• Sacred grooves are places of worship where their exploitation or destruction is not allowed by worshipers. eg: Kumaon areas, Khasi hills (Meghalaya), Aravalli hills (Rajasthan), Western ghats (Kerala, Karnataka).
• They are the last refuges for a large number of rare and threatened plants and species only because of its freedom from exploitation.

Question 8.
Among the ecosystem services are control of floods and soil erosion. How is this achieved by the biotic components of the ecosystem?
Answer:
Ecosystem services regulate and protects ecosystem that are essential for maintaining climate and ecology of area.
Control of soil erosion

• Plant roots hold soil particles firmly.
• Plant cover protects soil from erosion by wind and water.
• Plants increases porosity and fertility of the soil.

Control of floods It is carried by retention of water and prevention of runoff. Litter and humus of plants acts as sponge to retain rainwater. Plants hold soil, so prevents soil erosion. Rainwater does not run – off, so prevents flood as they filter water into soil.

Question 9.
The species diversity of plants (22%) is much less than that of animals (72%). Give explanation.
Answer:

• Plants are fixed and need fewer adaptations and little competition to obtain optimum raw materials and sunlight. So little diversity.
• But in Animals, they are mobile, they converge on single piece of vegetation, so comes competition that leads to species variation, so has more diversity in animals.

Question 10.
Can you think of a situation where we deliberately want to make a species extinct? How would you justify it?
Answer:
Some species are harmful to human eg: HIV, Small pox vires etc. Such species are not part of any food chains or webs. So, their extinction will not effect ecosystem. And also their extinction can be beneficial to humans. eg:- HIV, small pox vires, plasmodium species etc.

2nd PUC Biology Biodiversity and Conservation Additional Questions and Answers

2nd PUC Biology Biodiversity and Conservation One Mark Question

Question 1.
What are endemic species?
Answer:
Those species which are confined to a particular region and are not found anywhere in the world are called endemic species.

Question 2.
Define biodiversity?
Answer:
The totality of genes, species and ecosystem of a given region i.e. the combined diversity at all the levels of biological organisation is called biodiversity.

Question 3.
Name some biodiversity hotspots in India
Answer:
Western Ghats, Himalayas, Indo-Burma region – Srilanka.

Question 4.
Which are three important components of biodiversity ?
Answer:
The three components or levels of biodiversity are

• Genetic diversity
• Species diversity and
• Ecological diversity. Ecological diversity has again 3 components – alpha diversity (with in community diversity), beta diversity (between community diversity) and gamma diversity (regional diversity).

Question 5.
Amazon rain forest has the greatest biodiversity on earth. List any two hypothesis that are proposed by the biologists to account for the greater biological diversity.
Answer:
In tropics:-

• No Catastrophes – In tropics, there has been no catastrophes but is temperate areas glaciations and other catastrophes have caused large scale of destruction.
• Non-seasonal Environment – In tropics, seasons are nearly uniform. It promotes rich and increases species diversity.
• Solar Energy – Tropics get lots of sunlight which enhances productivity.

Question 6.
In the pie chart (A) and (B) drawn below to show the global animal diversity, which groups of animals would you name and write on the areas shaded black in (A) and (B). In which kind of habitat would you find these groups of animals
Answer:
(A) Insects Habitat, Mostly terrestrial
(B) Fishes Habitat, Aquatic.

Question 7.
What’s species diversity?
Answer:
The variety of species within a given region is called the species diversity.

Question 8.
Name the unlabeled areas ‘a’ and ‘b’ of the pie chart representing the global diversity of invertebrates showing their proportionate number of species of major taxa (Delhi 2009)

Answer:
(a) Insects
(b) Molluscs

Question 9.
Name the unlabeled areas ‘a’ and ‘b’ of the pie chart representing the biodiversity of plants showing their proportionate number of species of major taxa. (AI2009)

Answer:
(a) Fungi
(b) Angiosperms.

Question 10.
Name the unlabeled areas ‘a’ and ‘b’ of the pie chart representing the biodiversity of vertebrates showing the proportionate number of species of major taxa. (CBSE 2009)

Answer:
(a) Fishes
(b) Amphibians.

Question 11.
Name 2 animals that have become extinct by over exploitation by humans.
Answer:
Steller’s sea cow and passenger pigeon.

2nd PUC Biology Biodiversity and Conservation Two Marks Questions

Question 1.
Write the scientific name of the plant that yields reserpine. How is genetic variation expressed in this plant?
Answer:

• Rauwolfia vomitoria is the plant that yields reserpine.
• The genetic variation is shown in terms of the potency and concentration of the active chemical reserpine.

Question 2.
What does the term genetic diversity refer to? What is the significance of large genetic diversity in population?
Answer:
The term genetic diversity refers to the diversity of genes within a species.
It is important because

• Greater the genetic diversity among the organisms of a species, more sustenance, has against environmental perturbations.
• Genetically uniform populations are highly prone to diseases and harsh environment.

Question 3.
Explain co-extinction.
Answer:
It is a phenomenon in which when a species becomes extinct, the plant and animal species associated with an obligatory manner also become extinct. eg:- When a host fish becomes extinct, its unique assemblage of parasites also faces extinction.

Question 4.
Differentiate between zoological and national parks
Answer:

Zoological park	National park
These are the areas where the threatened animals are kept under conditions very similar to their natural habitat.	These are large areas where animals and plants are protected in their natural habitat.
It is an exsitu method os conser­vation.	It is an insitu conservation method.

Question 5.
What are biosphere reserves? How many of them are present in India?
Answer:
Biosphere reserves are the ecologically unique and bio-diversity rich regions that are legally protected. There are 14 biosphere reserves in India.

Question 6.
Why does the introduction of alien species into an ecosystem cause loss of biodiversity.
Answer:
The alien species become invasive and resources, so there is a decline in the indigenous species.

Question 7.
Name the region of the earth called the “lungs of the planet”. Mention giving reasons, the activities which are being carried out in this region now.
Answer:
Amazon forest is called the “lungs of the planet”. Human activities which are being carried out in this region are

• Grazing of beef cattle
• Cultivation of soya bean crop.

Question 8.
When and where the convention on biological diversity (earth summit) was held? While its aim.
Answer:

• The earth summit was held in Rio de Janeiro in 1992.
• The aim was to make the nation to take appropriate measures for conservation of biodiversity and sustainable utilization of its benefits.

Question 9.
What are sacred groves? Where are they found in India?
Answer:
Sacred groves are the tracts of forests that are set a side where all the trees and wild life are venerated and given a complete protection.
In India sacred grooves are found in

• Kashi and Jaintia Hills in Meghalaya
• Aravalli hills of Rajasthan
• Western Ghat regions of Karnataka and Maharashtra.
• Sarguja, Chanda and Bastar areas of M.R
• Sarpakavu of Kerala.

Question 10.
Name the following
(a) The group of animals that is maximum among vertebrates
(b) The scientist who coined the term biodiversity
(c) the lungs of the planet earth
(d) The region in India where maximum number of amphibians are present.
(e) The most species rich taxonomic group of animals.
Answer:
(a) Fishes
(b) Edward Wilson
(c) Amazon forest
(d) Western ghat
(e) Insect.

2nd PUC Biology Biodiversity and Conservation Three Marks Questions

Question 1.
Differentiate between In situ conservation and Ex situ conservation.
Answer:
In situ conservation:- It is the method of protecting the endangered species of plants or animals in the natural habitat either by protecting or cleaning up the habitat itself or by defending the species from predators.

• It helps in recovering populations in the surroundings where they have developed their distinct features.

Ex situ conservation :-

• It is the method of protecting the endangered species of plants or animals by removing them from the unsafe or threatened habitat and placing under the care of humans.
• It helps in recovering or preventing their extinction under stimulated conditions.

Question 2.
What are the characteristics of a stable community?
Answer:

• A stable community does not show much of variation in productivity from year to year.
• Such a community must be either resistant or resilient to occasional disturbances both natural and man made.
• It must be resistant to invasions by alien species.

Question 3.
Differentiate between Genetic diversity and species diversity.
Answer:

Genetic diversity	Species diversity
(a)  It is trait of the organisms. (b)  It represents the variety of genetic informations present in the organisms. (c)  It is important for adaptation to enviro­nment and changes occurring in it.	(a) It is trait of the biotic community. (b) It is variety of species and their abundance found within a region. (c) It influences the stability of the ecosystem.

2nd PUC Biology Biodiversity and Conservation Five Marks Question

Question 1.
What is the influence of biodiversity on the ecosystem? Mention the 3 possible consequences that loss of biodiversity in region can lead to.
Answer:
Influences of biodiversity

• The ecosystems with more species diversity show less year to year variation in total biomass production.
• The ecosystem with species diversity show more productivity compared to these with less species diversity.

Consequences are
The loss of biodiversity can lead to

• A decline in the crop productivity
• An increased variability in certain ecosystem
• A decreased resistance to environmental perturbates like drought.

Question 2.
How is the ‘sixth episode of extinction ‘of species on earth now currently in progress different from the five earlier episodes? Explain the various causes that have brought about this difference.
Answer:
Five episode of mass extinction have occurred during the past geological history of the earth due to natural phenomena like a continental draft, ice age, hitting of large
asteroids, global warming etc. But the sixth episode of mass extinction is due to human activities by knowingly or unknowingly ie. it is anthropogenic in origin, eg:- Destruction of tropical forests leads to destroy 14000-40000 species every year or 295% of species every hour.
Causes of these extinction may be.

• Habitat loss
• Habitat fragmentation
• Over exploitation of natural resources
• Introduction of alien species or exotic species which invade maximum space.
• Pollution due to human activity
• Commercial forestry.

Question 3.
Who proposed the rivet popper hypothesis? Explain the same with reference to ecosystem.
Answer:
This hypothesis was proposed by Paul Ehrlich.

• In an airplanes (ecosystems), all parts are joined together by using thousands of rivets (species).
• If every passenger travelling in this ecosystems causes the extinction of atleast one species (starts popping a rivet to take home), it may not be safer but if more and more rivets are removed, the plane becomes dangerously weak over a period of time.
• Further which rivet is removed may also be critical, loss of those on the wings is obviously a series threat to flight safety than those of a few on the seats or windows.
• Similarly, loss of key species, which run the ecosystem properly, is obviously a more serious threat to the ecosystem than other species.

Question 4.
Describe different methods of Ex-situ conservation
Answer:
In ex – situ conservation the threatened species of plants and animals are taken out of their natural habitat and placed in special settings where they can be protected and given special care.

(1) Zoological parks – The places where many animals that have become extinct in the wild, continue to be maintained.

(2) Botanical gardens – The place where many endangered and threatened species of plants are kept. It allows other plants which are used for reference or project purposes. In India there are 35 botanical gardens.

(3) Cryopreservation  – It is the storage of materials at ultra low temperature of -196°C either by rapid cooling or by gradual cooling and simultaneous dehydration at low temperature.

(4) Tissue culture and micro propagation – This method is used for preserving the germplasm and growing a number of plants from small parts of organs.

(5) Seed banks – Seeds of different genetic varieties of commercially important plants can be kept for long periods.

Question 5.
Which are the different “methods of in situ conservation?
Answer:
In situ conservation is the process of protecting the whole ecosystem and its biodiversity at all levels.

The endangered species of plants and animals are protected in their natural habitat without disturbing them from their own habitat. It helps in recovering the population in the surroundings where they have developed their distinctive features.

• Hotspots -These are the regions with high levels of species richness and high degree of endemism to provide maximum protection.
• Biosphere reserves – These are ecologically unique and biodiversity rich regions that are legally protected. In India there are 14 biosphere reserves.
• National park and wild life sanctuaries- These are the places where animals are in
  their own undisturbed habitat but protected these areas by law.
  In India there are 90 national parks and 448 wild life sanctuaries are there.
• Sacred groves – These are some patches of forest where all the trees and wild life with in are venerated and given total protection, eg: Sarpakavu in Kerala. Sarguja area of M.P. etc.

 

You can Download Chapter 14 Ecosystem Questions and Answers, 2nd PUC Biology Question Bank with Answers, Karnataka State Board Solutions help you to revise complete Syllabus and score more marks in your examinations.

Karnataka 2nd PUC Biology Question Bank Chapter 14 Ecosystem

2nd PUC Biology Ecosystem NCERT Text Book Questions and Answers

Question 1.
Fill in the blanks.

(a) Plants are called as because they fix carbon dioxide.
(b) In an ecosystem dominated by trees, the pyramid (of numbers) is type.
(c) In aquatic ecosystems, the limiting factor for the productivity is
(d) Common detritivores in our ecosystem are
(e) The major reservoir of carbon on earth is
Answer:
(a) Producers
(b) Spindle
(c) light
(d) Earthworms ants and mites
(e) Oceanic.

Question 2.
Which one of the following has the largest population in a food chain?
(a) Producers
(b) Primary consumers
(c) Secondary consumers
(d) Decomposers
Answer:
(d) Decomposers can have maximum number but not included in food chain.
So (a) Producers is the answer.

Question 3.
The second trophic level in a lake is-
(a) Phytoplankton
(b) Zooplankton
(c) Benthos
(d) Fishes
Answer:
(b) Zooplankton

Question 4.
Secondary producers are
(a) Herbivores
(b) Producers
(c) Carnivores
(d) None of the above
Answer:
(a) Herbivores

Question 5.
What is the percentage of photosynthetically active radiation (PAR), in the incident solar radiation?
(a) 100%
(b) 50 %
(c) 1-5% .
(d) 2-10%
Answer:
(b) 50%.

Question 6.
Distinguish between
(a) Grazing food chain and detritus food chain
(b) Production and decomposition
(c) Upright and inverted pyramid
(d) Food chain and Food web
(e) Litter and detritus
(f) Primary and secondary productivity
Answer:
(a) Grazing food chain and detritus food chain

Grazing food chain	Dertritus food chain
1. Also known as Predator prey food chain.	1. Also known as Saprotrophs food chain.
2. It is a common food chain where producers are eaten by herbivores, herbivore by carnivore and the latter by higher-order carnivore. Eg: Grass→grass hopper → frog →Snake → Vulture.	2. It proceedes from dead bodies and organic remains. Eg: Decaying plant matter → earth worm-) bird →Snake → Vulture.
3. It binds the inorganic nutrients into organic matter.	3. It releases the inorganic nutrients bound up in organic  matter.
4. It adds organic matter to dertritus food chain	4. Provides inorganic nutrients to grazing food chain.

(b) Production and decomposition

Production	Decomposition
1. It is the pheno­menon of synthesis of fresh biomass. 2. It locks up inor­ganic nutrients into the biomass. 3. It traps energy.	1. It is the pheno­menon of degra­dation of waste organic matter. 2. It releases inor­ganic nutrients from the organic matter into the environment. 3. It releases energy.

(c) Upright and inverted pyramid

Up right pyramid	Inverted pyramid
It is the ecological pyramid where the producers form a broad base and the consumers keep decreasing (in energy number or biomoss)	It is the ecological pyramid, where the producers form a narrow base while the consumers keep increasing (in number of biomass)

(d) Food chain and Food web

Food chain	Food web
1. Food chain refers to the transfer of energy from the producers through a series of organisms. 2. It is less realistic in nature	1. A number of inter connected food chains constitute a food web. 2. It is more realisitc in nature.

(e) Litter and detritus

Litter	Detritus
1. Freshly fallen parts of plants dead parts of plants,and animals and faecal matter of animals  which haven’t straped to decompose, constitute litter.	1. Freshly fallen and dead parts of plants and animals and faecal matter that have started to decompose constitute detritus.

(f) Primary and secondary productivity

Primary productivity	Secondary productivity
1. It is rate at which matter is built up by producers. 2. It is due to photosynthesis 3. There is net gain if energy in the biosphere	1. It is rate at which matter is built up by consumers. 2. It is due to herbiviores and predation. 3. There is no such activity

Question 7.
Describe the components of an ecosystem.
Answer:
An ecosystem has two types of components biotic and abiotic.
(1) Biotic components:- There are living organisms present in an ecosystem. On the basis of their obtaining food, biotic components are of 3 types – produces, consumers and decomposers.

• Producers – They are autotrophic components that includes phytoplankton, some algae floating, submerged and marginal plants.
• The consumers are the organism like zooplankton, free swimming animals, bottom dwelling animals etc consumes producers as their food.
• The decomposers are organisms (saprophytic) which obtain nourishment from
  organic remains they digest the organic remains by digestive enzyme and liberates inorganic nutrients. Because of this decomposers are called as mineralisers.

2. Abiotic components:- They are factors and materials of the physical environment. The materials include inorganic nutrients and organic remains. The organic remains consists of human substances, carbohydrate, lipide, proteins etc. The abiotic materials are air, water and soil.

Question 8.
Define ecological pyramids and describe with examples, pyramids of number and biomass.
Ans:
Ecological pyramids They are the graphical representations of various ecological parameter at the successive trophic levels of food chains with producers at the base top carnivores at the apex and intermediate levels .in between. Quantity at each level is indicated by length of bar in the graph. The pyramids are therefore also called bar diagrams.

Pyramids of number

It is graphical representation of numerical strength of various populations in different trophic levels per unit area of an ecosystem with producers forming base intermediate levels forming intermediate tiers and apex formed by top carnivores length of bar at each trophic level is proportional to the number of individuals at this level.

Pyramid of biomass
Biomass is the amount of living matter measured in terms of fresh or dry weight. Dry weight is preferred as it avoids seasonal variations in moisture content of biomass.

Pyramid of biomass is the graphical representation of amount of biomass per unit area sequence wise in rising trophic levels with producers at the base and top carnivores at the apex. Length of the bar indicates the comparative amount of biomass at that trophic level. Biomass, is maximum in producers. Only 10% to 20% biomass is passed from producer level to herbivore level.

Question 9.
What is primary productivity? Give brief description of factors that affect primary productivity.
Answer:
Primary productivity:- It is the rate of synthesis of biomass by producers per unit time per unit area through, the process of photosynthesis.
Factors:- It depends up on sunlight, temperature moisture, nutrients and photosynthesis efficiency of producers.

(1) Sunlight:- In tropical regions maximum sunlight is available. It reduces towards the pole. Therefore more photosynthesis and high productivity occurs in tropics.

(2) Temperature:- Temperate forest have lesser productivity as compared to tropical forest due to cold climate during winter. Alpine and arctic regions have very low productivity because of low temperature almost through out the year.

(3) Moisture:- Good rain and humidity increase productivity of the ecosystem with the fall in availability of water the productivity decreases.

(4) Nutrients:- A regular availability of nutrients is required for sustaining plant growth and hence the productivity of an ecosystem.Coral reefs and esturies are highly productive as the nutrient supply is rich.

5. Photosynthetic efficiency:- Some plants are photosynthetically more efficient in trapping sunlight than others. eg: Sugarcane.

Question 10.
Define decomposition and describe the processes and products of decomposition.
Answer:
The process of physical and chemical breakdown of complex organic remains into inorganic raw materials (CO₂, H₂O, minerals) for recycling is called decomposition. It is carried out by organism remain are called detritus.
There are types decomposition process occurs.
(a) Fragmentation
(b) leaching and
(c) Catabolism
(a) Fragmentation of Detritus:- Small invertebrates animals called detritivores comes out in highly pulverised state in their faeces.

(b) Leaching:- Part of soluble substances present in the fragmented and decomposing detritus get leached to upper layers of soil by percolating water.

(c) Catabolism:- It is carried out by saprotrophic bacteria. They secrete digestive enzymes over the fragmented detritus. The enzymes change the complex organic compounds into Simple compounds.

Catabolic action forms two types of products- humus and inorganic the process involved in formation of these products are respectively called humification and mineralisation.

Question 11.
Give an account of energy flow in an ecosystem.
Answer:
Energy flow:- The passage of energy through various trophic levels of an ecosystem is called energy flow. Their is no circulation of energy. Instead unidirectional flow of energy occurs in the ecosystem.

(1) Capture of energy:- Under favorable conditions 1-5% solar radiations is captured by producers and used for photosynthesis. It is gross primary productivity some 20% this is used by producers in their own activities. The net primary productivity available to herbivores. 8-4% of incident radiations.

(2) Transfer to herbivores:- Herbivores get a part of net primary productivity. The remaining is changed into detritus which is a source of energy to decomposers. Herbivores waste a lot of food energy during ingestion about 30% food energy is used up by herbivores for their life activities and liberated as heated. The remaining is used in building biomass of herbivores. It is about 10% of productivity of producers. The transfer of about 10% of biomass energy from one tropic level to the next tropic level is called 10% law (ten percent law).

(3) Transfer to Primary carnivores:- Host of the herbivores are eaten by primary carnivores. A lots of energy wastage occurs during the predation. About 60% of assimilated food energy is used up by primary carnivores for their external activities. Rest amount of energy is transferred to Secondary carnivores.

(4) Transfer of energy to higher level carnivores:- 10% of biomass energy available at the level of primary carnivore becomes incorporated into biomass of secondary carnivores. If there is a still higher level carnivore, it uses 10% of biomass energy present at the level of secondary carnivores. As energy available at higher carnivore level becomes small, an ecosystem doesn’t have more than 3-5 trophic levels. eg….

Question 12.
Write important features of a sedimentary cycle in an ecosystem.
Answer:
Sedimentary Biogeochemical cycle:- It is circulation of a biogeochemical between biotic and abiotic compound of an ecosystem is a nongaseous being lithosphere or sediments of the earth. Sedimentary cycles occur in case of phosphorus, calcium, magnesium, zinc, copper etc.

Important feature:

(i) Input of Nutrients:- Nutrients enter the nutrient pool through weathering of rocks. In sites soil formation also occur through weathering of rocks. Nutrients present in the soil become available to plants. Wind carries nutrients from mining areas and industrial area and deposited over the soil.

(ii) Internal nutrient cycling:- It is cycling or circulation of nutrients with in the ecosystem. Plants absorb nutrients from soil and incorporate them into organic matter. In the form of organic matter the nutrients pass from producers to herbivores and herbivores to carnivores. The process is called transfer. All trophic level pass a part of organic matter as detritus.

Detritus acted up on by decomposers and release the nutrients back into cycling pool. In stable ecosystems, over 80% of nutrient requirement of the biotic is met through internal nutrient cycling.

(iii) Out put of Nutrients:- It is a movement of nutrients out of an ecosystem. Out put reduces the availability of nutrients in the cycling pool. It occurs through soil erosion, run off water and economic out put like harvesting of crops or removal of wood from forest. Crop fields are always under negative nutrient budget.

Question 13.
Outline salient features of carbon cycling in an ecosystem.
Answer:
Carbon is the most abundant element as it occurs in every organic substances. It form 49% of the dry weight of organic matter. Carbon occurs as free carbon dioxide in atmosphere and dissolved as CO₂ in hydrosphere. Carbon dioxide is being added to the cycling pool of atmosphere and hydrosphere through two processes, biological and non- biological

Biological- All living organisms produce carbon dioxide through respiration Carbon trapped in organic matter is released as CO₂ during its decomposition.
Non Biological – Combustion or burning of biomass and fossil fuels produce carbon dioxides.

2nd PUC Biology Ecosystem Additional Questions and Answers

2nd PUC Biology Ecosystem One Mark Question

Question 1.
Define ecosystem.
Answer:
An ecosystem is a functional unit of nature, where living organisms (biotic) interact among themselves and also with the abiotic factors or their physical environment.

Question 2.
Give 2 man made ecosystem.
Answer:
Pond, crop fields

Question 3.
What is net primary productivity of an ecosystem. (CBSE Delhi 2005)
Ans:
It is the rate of energy stored or biomass accumulated by the producers. It depends up on rate of photosynthesis as well as respiration.

Question 4.
What PAR?
Answer:
The part of incident solar radiation that can be absorbed and used by plants autotrophs for photosynthesis, is called photosynthetically active radiation (PAR).

Question 5.
Name a dominant producers in a deep aquatic ecosystem. What other name could you give to a primary consumer, (AT 2007)
Answer:
Phytoplanktons or certain algae are the dominant producers in a deep aquatic ecosystem.
Primary consumers are known as herbivores.

Question 6.
What do the detritus food chain begin with?
Answer:
Detritus food chain begins with dead organic matters.

Question 7.
Why type of nutrition is shown by decomposers?
Answer:
Saprophytic nutrition.

Question 8.
What term is given to the inter connected food chain?
Answer:
Food-web.

Question 9.
What do mean by “Ten percent law”?
Answer:
Ten percent law states that only 10% of the energy is transferred from one trophic level to the next trophic level through food chain.

Question 10.
Identify the type of ecological pyramids shown here?
Answer:

• Pyramid of number in a tiee ecosystem.
• Pyramid of biomass in an aquatic ecosystem.

Question 11.
What do you mean by ecological succession?
Answer:
It is the phenomenon of gradual and fourly predictable changes in the species composition of a given area leading ultimately to the establishment of a climax community.

Question 12.
Define the term “Sere1
Answer:
The entire sequence of communities that successively change and lead to the establishment of a climax community is called a sere.

Question 13.
Define the term ‘climax community”?
Answer:
The community that is in near equilibrium with the environment, and does not undergo much change and occupied a large area is called climax community.

Question 14.
What do you mean by ‘Pioneer species’?
Ans:
The species that invades a bare area and starts establishing a community is called pioneer species.

Question 15.
Name the pioneer species
(1) On a bare rock
(2) In a water body (CBSE foreign 2008)
Answer:

1. Lichen
2. Phytoplankton.

Question 16.
What is the structure and composition of a community expected to remain unchanged.
Answer:
Un disturbed climax community

Question 17.
In the pyramid of biomass given below, name 2 types of crops
(i) One which is supported and
(ii) One which supports. In which ecosystem such type of pyramids found.

Answer:
(i) primary producer (phytoplankton)
(ii) primary consumer (zooplankton)
In aquatic ecosystem such type of pyramid found.

Question 18.
Give an example of an inverted ecological pyramid, what kind of pyramid of energy would it have?
Answer:
Inverted ecological Pyramid Pyramid of numbers based on large tree as a producer supporting a number of herbivorous birds each having a number a number of parasites.

2nd PUC Biology Ecosystem Two Marks Questions

Question 1.
In the following table the ecological units are mentioned in the first coloumn vertically and their attributes are mentioned horizontally. Match the ecological unit and its attribute and put a tick mark in the blanks with the table

Answer:

Question 2.
Match the column A with any two of column B

Answer:

Question 3.
Differentiate between primary succession and secondary succession. (CBSE 2006)
Answer:

Primary seccession	Secondary seccession
(1) It occurs in biologically sterile area.	(1) Occurs in an area which is biologically quite fertile
(2) Humus/organic matter is absent in the early stages	(2) Present from very begining.
(3) It begins on a soilless area.	(3) Occurs on a area having sufficient soil.
(4) It takes long time ie. 1000 years and more.	(4) It takes place in  lesser time 50-200 years.

Question 4.
Differentiate between standing crop and standing state (CBSE 2008)
Answer:

Standing crop	Standing state
(1) It is the amount of living matter or biomass of biotic components of an ecosystem.	(1) It is the amount of inorganic nutrient  present in an ecosystem.
(2) It is present all over the ecosystem.	(2) It occurs in the growth medium of producers.
(3) It indicates the productivity of the ecosystem.	(3) It determines the productivity of the ecosystem.

Question 5.
Mention four functional aspects of in ecosystem.
Answer:
The four functional aspects of an ecosystem are

• Productivity
• Decomposition
• Energy flow
• Nutrient cycling.

Question 6.
Define Productivity? How is it expressed?
Answer:
Productivity refers to the rate of biomass production.
It is expressed as g^-2 yr^-2 or (Keal m^-2) yr^-1

Question 7.
Differentiate between Gross primary productivity and Net primary productivity.
Answer:

Gross Primary productivity (GPP)	Net Primary productivity (NPP)
It is the rate of produ­ction of biomass/organic matter by producers during photosynthesis	It refers to the biomass or organic matter available at the producer level to the primary consumers i.e. GPP (Respiration losses)

Question 8.
Write the factors which determine primary productivity.
Answer:
Primary productivity depends on

• The photosynthetic capacity of the plant species.
• Availability of nutrients
• Amount of sunlight available
• Water availability and temperature.

Question 9.
What would happen to the successive trophic levels in the pyramid of energy, if the rate of reproduction of phytoplanktons was slowed down? Suggestion in phytoplankton reproduction. (CBSE Delhi 2006)
Answer:
As phytoplanktons are the producers in the ecosystem, the amount of energy available for transfers will decrease. Organisms at successive trophic levels will also decrease. ‘
The two factors responsible for reduction in phytoplankton population are

• Low nutrients and
• Less availability of oxygen.

Question 10.
It is stated that the pyramid of energy is always upright. Justify (Delhi 2008)
Answer:

• The base of the pyramid of energy is occupied by producers, which have the maximum amount of energy.
• When energy flow from one trophic level only 10% is transferred, there is always loss of some energy in the form of heat.
• So, the amount of energy at higher trophic level will always be less than the lower trophic levels and pyramid of energy will be upright and be inverted.

Question 11.
Differentiate between Hydrarch succession and Xerarch succession

Hydrarch succession	Xerarch succession
1. The ecological succession that starts in water bodies and proceeds to mesic condition is called hydrarch succession 2. Phytoplantation form the pioneer community.	1. The ecological succession, that starts With bare rocks xeric coditions and proceds to mesic condition is called  Xerarch succession. 2. Lichens form the pioneer community.

Question 12.
Why does the secondary succession is faster than primary succession.
Answer:

• Secondary succession occurs in an area or place where life had existed before, but had been some how wiped out.
• some soil and organic sediments are already present, hence succession is faster Primary succession occurs in an area where no life existed before. It takes time for the formation of soil and so succession takes more time.

Question 13.
Differentiate between carbon cycle and phosphorus cycle
Answer:

Carbon cycle	Phosphorus Cycle
1. The reservoir of carbon cycle is the atmosphere as carbon dioxide and also the lithosphere, as fossil fuel. 2. There is respiratory release of CO2	1. The reservoir of phosphorus cycle is the  phosphate containing rocks of lithosphere 2. There is no respiratory release of phosphorus.

Question 14.
Differentiate between production and decomposition
Answer:

Production	Decomposition
1. It is the process of the formation of biomass or organic matter from simpler inorganic substance 2. It occurs at the level of producers and consumers.	1. It is the proses of the breakdown of larger organic molecules into simple molecules and ultimately into inorganic substances. 2. It occurs at the level of decomposers.

Question 15.
Name the pioneer species on a bare rock. How do they help in establishing ?
Answer:
Lichens are the pioneer speciesin succession on a bare rock. The lichens secrete certain acids to corrode the rock and help in weathering of rocks and soil formation; thus they pave way to some plants like bryophytes. The climax community will be a mesic forest.

Question 16.
Differentiate between Gaseous and sedimentary cycle.
Answer:

Gaseous cycle	Sedimentary Cycle
1. The reservoir of gaseous cycle lies in the atmosphere 2. Exchange occurs in the form of gases between the living and nonliving comp­onents of the ecosystem.	1. The reservoir of sedimentary cycle lies in the lithosphere 2. Exchange occurs mainly in the form of dissolved nutrients between the non-living and the living components.

Question 17.
In the terrestrial ecosystem the detritus food chain (DFC) and the grazing good chain (GFC) become inter linked. Justify the above statement. What term is given to such interconnection? (HOTS)
Answer:

• Certain organisms of the GFC are predators to certain animals of DFC. As a result the food chains become interconnected.
  eg. earth worms which are detrivores are eaten by small birds (DFC) which become prey to vultures/kites or even cats of the GFC.
• Organisms like cockroaches and cows, which are omnivores play an important role in the interconnections of food chain constitute a food web.

2nd PUC Biology Ecosystem Three Marks Questions

Question 1.
Describe the factors that control decomposition ?
Answer:
Decomposition is controlled by
(i) Chemical composition of detritus

• Decomposition is faster when detritus is rich in nitrogen and water soluble substances like sugars.
• Decomposition is slow, when detritus is rich in lignin and chitin.

(ii) Temperature and soil moisture, through their effects on the activities of microbes.

• Warm and moist environment favour decomposition.
• Low temperature and absence/reduced moisture levels inhibits decomposition.

(iii) Oxygen

• Decomposition is an oxygen consuming process
• Anaerobic condition inhibits decomposition.

Question 2.
Represent schematically the decomposition cycle in a terrestrial ecosystem
Answer:

Question 3.
What is humus? Mention its properties.
Answer:
Humus is a dark coloured, amorphous substance produced by the process of humification during decomposition of detritus.
Properties of humus:-

• It is highly resistant to microbial action and under goes decomposition at an extremely slow rate.
• Being colloidal in nature, it serves as a reservoir of nutrients.
• It improves the water holding capacity of soil.
• Further decomposition of it provides inorganic nutrients to the plants.

Question 4.
A given species may occupy more than one trophic level in the same ecosystem at the same time. Explain with an example (2008)
Answer:
A snake eating a mouse in a field/lawn occupies the third trophic level in the food chain.
Plants → Mice → Snake
When the snake eats frog in the same field, it occupies the 4th trophic level in a food chain it is because the frog feeds on some of the insects which depends on the plants.
Plants → Insects → Frog → Snake
Thus in the same ecosystem one animal (snake) occupies more than one trophic level at the same time as it cannot satisfy its food need from one trophic level.

2nd PUC Biology Ecosystem Five Marks Question

Question 1.
(a) Mention 2 human activities that affect carbon cycle
(b) What are the different ways in which CO₂ is added to the atmosphere ?
(c) How does the chemical nature of detritus determine the rate of decomposition.
Answer:
(a) The major human activities that influence carbon cycle are

• Burning of fossil fuels.
• Deforestation

(b) CO₂ is added to the atmosphere in the following ways:

• Burning of fossil fuels
• Volcanic activity
• Forest fire
• Respiratory activities

(c)

• If the detritus is rich in lignin and chitin the decomposition is slow.
• If the detritus rich in nitrogen and water soluble substances like sugars, decomposition is faster.

Question 2.
Explain the different steps in the process of decomposition.
Answer:

• Fragmentation:- It is the process of breaking of the detritus into smaller particles by detrivores like earth worm.
• Leaching:- It is the process in which water soluble inorganic substances rundown into soil horizon and get precipitated as salts.
• Catabolism:- The enzymatic conversion of the detritus into simple organic compounds and then into inorganic compounds is called catabolism.
  The enzymes are secreted by the decomposers like bacteria and fungal.
• Humification:- Humification during decomposition leads to the accumulation of a dark coloured amorphous substance called, humus.
• Mineralisation:- It is the process in which the humus is degraded by certain micro organisms and the inorganic nutrients are released.

Question 3.
Describe the pond as an ecosystem.
Answer:

• A pond is a fairly self sustainable unit that shows even complex interactions of an aquatic ecosystem.
• It is a shallow water body in which all the major/basic components of an ecosystem are well exhibited.

The abiotic components include

• Water with all the dissolved inorganic and organic substances.
• The rich soil deposits at the bottom.
• The solar input.
• The cycle of day length and temperature
• Other elematic factors.

The biotic components include.

• The producers or autotrophic components that include phytoplanktons, some algae, floating, submerged and marginal plants.
• The consumers represented by zooplanktons free swimming animals, bottom dwelting animals etc.

Question 4.
Show schematically the energy flow through different trophic levels of an ecosystem.
Answer:

You can Download Chapter 13 Organisms and Populations Questions and Answers, 2nd PUC Biology Question Bank with Answers, Karnataka State Board Solutions help you to revise complete Syllabus and score more marks in your examinations.

Karnataka 2nd PUC Biology Question Bank Chapter 13 Organisms and Populations

2nd PUC Biology Organisms and Populations NCERT Text Book Questions and Answers

Question 1.
How is diapause different from hibernation?
Answer:

Diapause	Hibernation
(i) Dormant stage in development of an organism	(i) State of inactivity in a mature organism.
(ii) Occurs in summers and winters	(ii) Only during winters
(iii) Reduction in free water	(iii) No such adaptations

Question 2.
If a marine fish is placed in a freshwater aquarium, will the fish be able to survive? Why or why not?
Answer:
It will not be able to survive for long because:-

• Water will enter the body by endosmosis
• As marine fishes drink lots of water, so excess water enters.
• It does not have salt absorbing mechanism as of freshwater fishes.

So, these fishes will die because of problem in osmolarity maintenance But due to hormonal mechanisms, migratory fishes are exceptions as they withstand the changes eg:- Hilsa, salmon

Question 3.
Define phenotypic adaptation. Give one example.
Answer:
Phenotypic adaptation:- It is non-genetic change in physical and physiological characteristics which develops in response to changes in environment and are useful to organisms in adjustment to prevailing Pvt. conditions.
eg:-

• Mountain sickness in normal people in high attitudes but tribes living in himalayas do not have mountain sickness
• Euphorbia hirta plant species.

Question 4.
Most living organisms cannot survive at temperature above 450C. How are some microbes able to live in habitats with temperatures exceeding 1000C?
Answer:
Temperature > 45°C causes precipitation of protoplasm and denaturation of enzymes. Therefore they die in most of organisms But some live in 1000°C (thermophiles) due to

• Branched-chain lipids that reduce fluidity of cell membranes.
• Inborn metabolism to produce heat-tolerant enzymes
• Reduced free water.

Question 5.
List the attributes that populations but not individuals possess.
Answer:

• Population density
• Birth rate
• Death rate
• Sex ratio
• Population growth
• Age distribution
• Population dispersal.

Question 6.
If a population growing exponentially double in size in 3 years, what is the intrinsic rate of increase (r) of the population?
Answer:

Question 7.
Name important defence mechanisms in plants against herbivory.
Answer:
Defence is of 2 types Morphological and chemical Defences.
Morphological defence –

• Thoms, spines, prickles, bristles
• Stinging hair, sticky hair, hairy coating
• Harbowing ants
• Resemblance to dreaded animals.

Chemical Defences

• Latex
• Alkaloids
• Tannins
• Silica
• Bitter taste, Offensive smell
• Irritating substance
• Poisonous cardiac glycosides.

Question 8.
An orchid plant is growing on the branch of mango tree. How do you describe this interaction between the orchid and the mango tree?
Answer:
Commensalism – orchid being space parasite benefitting from mango plant in obtaining space for residence but mango tree is not harmed.

Question 9.
What is the ecological principle behind the biological control method of managing with pest insects?
Answer:
The ecological principle behind control of pest insects is controlling growth of their population through natural enemies, predator, parasites.

Question 10.
Distinguish between the following:
(a) Hibernation and Aestivation
(b) Ectotherms and Endotherms
Answer:

Hibernation	Aestivation
(i) Condition of passing the winter in a resting or dormant condition.	(i) State of inactivity during hot and dry summer.
(ii) Animal rests in warm place	(ii) Animal rests in cool, shady, moist place.
(iii) Lasts for whole winter.	(iii) Lasts for hot dry day because nights are often cooler

(b)

Ectotherms/Cold Blooded	Entotherms/Wann Blooded
(i) Unable to regulated their body temperature.	(i) Able to regulate their body temperature.
(ii) Lives in areas with favourable body temperature as they change their body temperature with respect to environmental temperature	(ii) Live in all places as there is only little effect on their body temperature by environmental temperature.
(iii) They show hibernation, aestivallon and are less active.	(iii) More active and no such inactive states are expressed

Question 11.
Write a short note on
(a) Adaptations of desert plants and animals
Answer:
(a)
(1) Plants vegetation is sparse, grows during rains only. (Drought exoping)
(2) Annuals (Drought evaders)
(3) Succulents (Drought resisting) – stores water with mucilage and latex.
(4) Non succulent perennials (Drought enduring) – long roots and avoids transpiration by modification.
(5) Modifications

• leaves as spines and thorns
• Stems as water storage body with thick bark
• Long, deep roots with shoot system

Animals

• Lives in burrows
• Very little water requirement and can store water in modified body parts.
• Urine is concentrated and faeces is nearly solid with very little water and metabolic water is also used by them as source of water.
• Nasal counter- Current mechanism preventloss of water during breathing with small nostril size.
• Feeds on dry seeds and rehydrates and stores water when they reach a water body.
• Very small body surface are a so very less sweating so less water loss from body.

(b) Adaptations of plants to water scarcity
Answer:
same answer as above (drought/desert animals or plants).

(c) Behavioural adaptations in animals
Answer:
Snakes – in winter, the snakes will come out of their burrows and bask in the sun to warm their body for activity.

Desert lizards keep their body temperature fairly constant by their behaviour changes. When their body temperature drops below comfort zone, they would come out of burrow and bask in sun.

(d) Importance of light to plants
Answer:
In plants light influences photosynthesis growth and reproduction height influences flower induction, seed germination plant movement etc.

(e) Effect of temperature or water scarcity and the adaptations of animals.
Answer:
Animals living in arid areas are adapted to manage with scarcity of available water and reduce water loss to minimum.

Eg: Kangaroo rat feeds on dry seeds. Animals protect themselves from excessive cold by hibernation, thick for, constriction of peripheral blood vessel.

Question 12.
List the various abiotic environmental factors.
Answer:

• Atmospheric factors- Light, temperature, water, wind, humidity.
• Edaphic factors- Soil texture, soil water, soil air, soil pH soil micro organisms, minerals.
• Topographic factors – Slope, altitude, valley.

Question 13.
Give an example for:
(a) An endothermic animal
(b) An ectothermic animal
(c) An organism of benthic zone
Answer:
(a) An endothermic animal – Monkey (mammal)
(b) An endethsmml animal Frog (amphibian), snake (reptile)
(c) An organism of benthic zone – Angle Fish

Question 14.
Define population and community.
Answer:
Population Nearly/relatively permanent aggregation or grouping of interbreeding individuals of the same species present in a particular space or area at a given time who share the same gene pool.

Community (Biotic or Biological Community) Assemblage of different species present in the same area at the same time which show interactions and interdependence through trophic and spatial relationships.

Question 15.
Define the following terms and give one example for each:
(a) Commensalism
(b) Parasitism
(c) Camouflage
(d) Mutualism
(e) Interspecific competition
Answer:
(a) Commensalism:- Interaction where one species is benefitted and the other is neither benefitted nor harmed is called commensalism, eg: Clone Fish living in company of sea Anemones.

(b) Parasitism:- It is interspecific interaction in which small sized organism of one species obtains nourishment and spends a part or whole Of its life on or inside the body of large sized organism of other species, eg: Plasmodium in human, liver fluke in snail and fish.

(c) Camouflage:- Phenomenon of blending with surroundings with similar colour, marking, shape etc. to escape from predators and preys eg: Stick insect, leaf insect.

(d) Mutualism:- Interaction confers benefits on both the interacting species, eg: Lichen (fungus + Algae); Rhizobium and legumes.

(e) Interspecific competition :- struggle against, members of different species for obtaining some resource (food, water etc) eg: roots of plant species in same area of a forest
→ It is a potent force in organic evolution.

Question 16.
With the help of suitable diagram describe the logistic population growth curve.
Answer:

Logistic growth occurs because of natural selection. Here nature selects the filter (Survival of the fittest). Nature has resource to support maximum number of people (Carrying Capacity (K)) beyond which resources won’t support them due to their lock. This explain that log phase follows phase of acceleration. So we get sigmoid curve.

This growth is Verhulst-pearl Logistic Growth
\(D=\frac { dN }{ dt } =rN\left( \frac { K-N }{ K } \right) \)

N=Population density at time
K = Carrying capacity
r = Intrinsic rate of natural increase

Question 17.
Select the statement which explains best parasitism.
(a) One organism is benefited.
(b) Both the organisms are benefited.
(c) One organism is benefited, other is not affected.
(d) One organism is benefited, other is affected,
Answer:
(d) One organism is benefited, other is affected,

Question 18.
List any three important characteristics of a population and explain.
Answer:
Characteristics are: Population density, population growth, age distribution, birth rate, death rate, sex ratio etc.
(1) Population density:- Indicates size of population. It is number of individuals of a population found in a unit area or space at a given time. It is found out by total count
Random sampling.
\(D=\frac { N }{ S } \)

D – Population Density
N – total number of individuals of given area
S- unit of space or area

(2) Population growth:- It is increase in size of the population over a period of time.
N_t = N_o+ (natality +Immigration) – (Mortality +Emigration)
N_t= N_o +B + I-(D + E)
N_t = Population increase after time t;
N_o= Population at t = 0

(3) Age distribution :- Pre-reproductive, reproductive, post – reproductive.
it helps to provide information about the population – Expending, Declining or Stable population.

2nd PUC Biology Organisms and Populations Additional Questions and Answers

2nd PUC Biology Organisms and Populations One Mark Question

Question 1.
Define the term ecology.
Answer:
It is study of the relationships of living organisms with the biotic and abiotic components of the environment.

Question 2.
Name the factors essential for the formation ‘ of major biomes
Answer:

• The annual variation in the intensity and duration of temperature
• The annual variation in precipitation, account for the formation of major biomes.

Question 3.
Which one of the two stenothermals or eurythermals, shows wide range of distribution, on earth and why? (CBSE 2008)
Answer:
Eurythermals show a wide range of distribution as they can tolerate and thrive in a wide range of temperatures.

Question 4.
Between amphibians and birds, which will be stable to cope with global warming? (AI2008)
Answer:
Birds will be stable because they are eurythermals, which can tolerate wide range of temperatures.

Question 5.
Why many of the fresh water animals cannot live for long in sea water or vice versa. (Delhi 2008)
Answer:
This is because of the osmotic changes in the body.

Question 6.
Define homeostasis
Answer:
It is the self regulatory mechanism to maintain the internal environment constant despite changes in the external environment.

Question 7.
How do herbs and shrubs survive under the shadow of big canopied trees in the forest ? (AI 2008)
Answer:
They are adapted to photosynthesis optimally under very low light condition and hence survive under the shadow of big canopied trees.

Question 8.
Why is the polar region not a suitable habitat for tiny humming birds ? (AI 2008)
Answer:
The small birds have larger surface area to body volume ratio and tend to lose heat fast when it is cold outside; consequently they have to spend more energy to generate body heat.

Question 9.
Define the term migration
Answer:
Migration is the temporary, long-distance or short distance movements of animals from the stressful movement to a less stressful or comfortable environment and return to the original habitat when the stressful period is over.

Question 10.
Define the term hibernation.
Answer:
It is the process in which animals spend the winter in an inactive/dormant state,
eg: Frogs, polarbear.

Question 11.
When and why do some animals (frog, polarbear) go into hibernation (Delhi 2008)
Answer:
When the animals (like frog) are not able to migrate from unfavorable or stressful condition/habitat during very cold condition, they hibernate to avoid the stress by escaping in time.

Question 12.
Define the term aestivation?
Answer:
It is the process in which animals spend the dry, hot summer period in an inactive state,
eg: Snails.

Question 13.
When and why do some animals undergo into aestivation?
Answer:
When the snails are not able to migrate from stressful habitat in summers they undergo aestivation to avoid stress by escaping in time.

Question 14.
Define the term adaptation.
Answer:
The development of certain features in an organism in response to particular environment which may improve the chances of survivals are called adaptation.

Question 15.
What is Allen’s rule?
Answer:
Allen’s rule refers to the minimising of heat loss in animals by possessing shorter ears and limbs.

Question 16.
Why do people living in high altitude have a higher red blood cell count or total haemoglobin
Answer:
To compensate for the low atmospheric pressure and low oxygen content of air prevailing at high attitudes, people have higher, RBC count or total haemoglobin.

Question 17.
List any 2 physiological responses that help you to gradually get acclimatised to high attitudes when you go from the plains (Delhi 2008)
Answer:

• Increasing in breathing rate
• Decreasing in binding capacity of haemoglobin.
• Increase in RBC production.

Question 18.
Define Population density.
Answer:
The total number of individuals of a species present per unit area or volume at a given time.

Question 19.
Give an example where population estimation of an organism is done indirectly with out actually counting the organism. (AI2008)
Answer:

• The number of fish caught in a trap indicates the total population density in a lake
• The tiger census is based on the pug marks or faecal pellets.

Question 20.
When does a population growth curve become sigmoid?
Answer:
Sigmoid growth curve represents logistic growth where growth is slow initially and then becomes rapid the curve becomes steady due to resources become tending.

2nd PUC Biology Organisms and Populations Two Marks Questions

Question 1.
Why is thermoregulation more effectively achieved in larger animals than in smaller ones?
Answer:
Larger ones achieve thermoregulation more effectively than smaller ones because of less surface area/volume ratio in larger ones, hence lose body heat slowly.

Question 2.
Which one out of eurythermal or stenothermal species is likely to survive increased temperature?
Answer:
Eurythermal species as they can tolerate wide variations in environmental temperature; but stenothermal ones live with narrow range of temperature only.

Question 3.
Study 3 representative figure of age pyramids

(a). Mention names given to the 3 kinds of age profile (i), (ii), (iii).
Answer:
(i) Expanding population (Triangular)
(ii) Stable population (Bell shaped)
(iii) Declining population (Cube shaped)

(b). Which one of them is ideal for population and why?
Answer:
We take stable population pyramid as ideal because our aim is to stabilize the population.

(c). How do such age profile studies help policy makers get concerned about growing population?
Answer:
Age pyramid/profile can indicate

• Rate of growth of population
• Increase in elderly population and reproductive aged people.

These features help prepare for future planning on:

• Stress of family planning
• To help elderly and needful people to live comfortably.

Question 4.
(a) Write eg: for Verhulst Pearl logistic growth
Answer:
\(\frac { dN }{ dt } =rN\left( \frac { K-N }{ K } \right) \)
r=intrinsic rate of natural increase
N = Population density at time (t)
K = Carrying capacity.

(b) Draw graph for a population whose population density has reached the carrying capacity.
Answer:

(c) Why is logistic growth model considered more realistic one for most animal populations?
Answer:
Logistic growth model is considered realistic in animals because each area has a carrying capacity beyond which environmental resistance grows and restrict their growth. It decreases natality and increases mortality.

(d) Draw growth curve where resources are not limiting growth of population?
Answer:

Question 5.
In adjacent population growth curves

Answer:
Curve (a) – Non-limiting
curve (b) – Limiting and has reached carrying capacity.

(ii) In absence of predators which curve will be demonstrated?
Answer:
Curve (a) because of absence of controlling factor.

Question 6.
Mention any two significant roles predation plays in nature. (AI2008)
Answer:

• Predation is the natural way of energy transfer through trophic levels in a food chain.
• Predation keeps the prey population under control of ecosystem.
• Predation maintains spicies diversity.

Question 7.
List any two adaptive features evolved in parasites enabling them to live successfully on their hosts. (Delhi 2008)
Answer:
The adaptive features of parasites include

• Loss of unnecessary sense organs
• Presence of adhesive organs or suckers to cling on to the host.
• Loss of digestive system
• High reproductive capacity.

Question 8.
Name the four major biomes found in India.
Answer:

• Tropical rain forest
• Tropical deciduous forest
• Desert
• Seacoast

Question 9.
Write the influence of temperature in the life of organism.
Answer:

• The temperature affects the enzyme reaction in bur body.
• The thermal tolerance of organisms determines their geographical distribution.

Question 10.
Differentiate between Euryhaline and ‘ Stenohaline animals.
Answer:
Euryhaline animals Animals which can tolerate a wide range of salinity. Stenohaline animals Animals which can tolerate a narrow range of salinity.

Question 11.
What is the effect of light in the life of animals.
Answer:

• Intensity and duration of light influences the activities like foraging, migratory activities and reproduction.
• light influences the temperature and there by the metabolism of animals.

Question 12.
How do human being maintain constant body temperature?
Ans:

• In summer we sweat profusely; the evaporation of the sweat cools the body and brings the body temperature down.
• In winter, we shiver and that produces more ‘ heat, to raise the body temperature.

Question 13.
Mention 2 adaptations the mammals of colder region have, to minimize the loss of body heat.
Answer:

• Mammals of colder regions have shorter ears and limbs.
• Aquatic mammals of colder seas have thick layer of fat called blubber below the skin which acts as insulator reduces the loss of body heat.

Question 14.
Differentiate between Population size and Population Density.
Answer:

• Population size:- The number of individuals of a species, in a given area at a given time.
• Population density:- The number of individuals of a population per unit area at a given time.

Question 15.
Biomass is a more meaningful measure of population size. Explain.
Answer:

• If the population is huge, the total number is not as easily adaptable measure as counting takes a very long time or counting becomes practically impossible.
• For some ecological investigations, there is no need to know the absolute population size / density.

Question 16.
Define carrying capacity.
Answer:
Carrying capacity is the maximum number of individual of a population that can be sustained by a given habitat.

Question 17.
What is the role of predators in maintaining species diversity in an ecosystem?
Answer:
Predators help in maintaining species diversity in an ecosystem or community by reducing the intensity of competition among the competing prey species.

Question 18.
In what ways the prey species are adapted to escape from predators? Explain with example.
Answer:

• Some species of frogs and insects are cryptically coloured or camouflaged to avoid being detected easily by the predators.
• Some prey species are poisonous and are avoided by the predators.

Question 19.
(a) How is Cuscuta adapted to be a parasitic plant?
(b) Why do cattles avoid browsing on Calotropis plants? Explain. (CBSE foreign 2009)
Answer:
(a)

• Cuscuta has no chlorophyll and leaves.
• It develops haustoria to derive nutrition from the host it parasites.

(b) Calotropis plants possess a highly poisonous cardiac glycoside, which is fatal to animals.

Question 20.
Name two basic types of competition found amongst organisms. Which one of these is more intense and why?
Answer:
The two types of competitions are

• Interspecific competition and
• Intra specific competition

In this intra specific competition is more intense because it is an interaction among individuals of same species for similar requirements.

Question 21.
Explain interference competition with an example.
Answer:
In interference competition, even if the resource is abundant, the feeding efficiency of one species is reduced by the interfering and inhibitory presence of other species.
Eg: The Abingdon tortoise in Galapagos islands become extinct with in a decade due to the introduction of goat in that island.

Question 22.
Differentiate between commensalism and Amensatism.
Answer:

• Commensalism:- It is the interspecific interaction in which one species is benefited while the other is neither benefited nor affected.
• Amensatism:- It is an interspecific interaction in which one species is affected, while the other species is neither benefited or affected.

Question 23.
What is resource partitioning ? Give an example.
Answer:
It is the phenomenons in which two species competing for the same resource could avoid competition by choosing different patterns of foraging and different times of feeding. Eg:- Five closely related species of warblers living on the same tree have been shown to co exist and avoid competition by behavioural differences.

Question 24.
Give the interaction present in each.
(a) Cuckoo lays her eggs in the crow’s nest
(b) Orchid grows on a mango tree
(c) Cuscuta growing on a shoe flower plant
(d) Clown fish living among the tentacles of sea anemone
(e) Ticks live on the skin of dogs
(f) Mycorrhizae living on the roots of higher plants
(g) Sea anemone is often found in the shells of hermit crab (CBSE-Delhi 2008)
Answer:
(a) Brood parasitism
(b) Commensalism
(c) Commensalism
(d) Commensalism
(e) Parasitism
(f) Commensalism
(g) Commensalism.

Question 25.
Name and explain the interaction between fig trees and certain species of wasps.
Answer:
The interaction between fig trees and certain species of wasp is mutualism.

• The female wasp uses the ovary of flowers as a site of oviposition (egg laying) and the developing seeds as flood for the larvae.
• The flower is pollinated when the wasp is searching a place for oviposition.

Question 26.
What type of interaction is there between clown fish and sea anemone. Why?(AI 2008)
Answer:
The interaction between clown fish and sea anemone is commensalism. In this, one is benefitted and the other is neither benefitted nor harmed.
In this relation
(i) The sea anemone has stinging tentacles which keeps away the predators of clown fishes in this clown fish is getting benefit and the sea anemone is not getting any benefit or not harmed.

Question 27.
\(D=\frac { dN }{ dt } =rN\left( 1-\frac { N }{ K } \right) \)
(a) Which type of growth curve does it represents,
(b) What do the following notations represent
(i) \(\frac { dN }{ dt } \) (ii) r (iii) N (iv) K (CBSE 2005)
Answer:
(a) It represents logistic or Verhulst-Pearl logistic growth
(b) \(\frac { dN }{ dt } \) = rate of change in population size
r – intrinsic rate of natural increase
N – Number of ex histing individual
K – Carrying capacity.

Question 28.
Study the population growth curves shown in the diagam

(1) Identify curves ‘a’ and ‘b’
(2) Mentions the conditions responsible for the curves ‘a’ and ‘b’ respectively
(3) Give the equation for the curve ‘b'(CBSE 2006)
Answer:
(1) a – Exponential curve
b – logistic or sigmoid curve

(2)
a – Unlimited food and other resources
b – Limited food and other resources

(3)
\(\frac { dN }{ dt } =rN\left( \frac { K-N }{ K } \right) \)

Question 29.
Study the table given below in regard to population interactions and the questions given below.

[(+) plus – beneficial interaction; (-) minus – detrimental interaction; 0 (zero) – neutral interaction.
(a) Identify the interactions a to e
(b) Explain each one. (CBSE 2008 comptt)
Answer:
A – B
(a) Amensalism – Species A harmed species B unaffected
(b) Predation/parasitism – Species A benefited species B harmed
(c) Competition – Species A and B mutually inhibited
(d) Mutualism – Both A and B benefitted
(e) Commensalism – Species A is benefitted Species B is unaffected.

Question 30.
Is the statement in correctly matched ? If it is incorrect, rewrite the correct form Camoflague : An organism showing resemblance with external environment animals or plants for the purpose of protection
Answer:
Incorrect:- Camoflague is blending with the back ground or surroundings due to similar colours, shape or marketing so as to remain unnoticed by predators (for protection) and prey (advantage).

2nd PUC Biology Organisms and Populations Three Marks Questions

Question 1.
What are Conformers? Why they haven’t evolved mechanisms for temperature regulation or osmoregulation.
Answer:
Conformers are those organism, which change their body temperature, osmolarity etc. according to the external ‘environmental conditions.
(1) During the course of evolution, the costs and benefits of maintaining a constant internal environment are taken into consideration, when it is not advantageous, the organisms have not evolved mechanisms to maintain homeastasis.

(2) Heat loss or gain is a function of surface area and hence very small animals are not found in polar region i.e. they have become distributed according to the external conditions.

(3) Similarly aquatic animals, that are conformers can change the osmolarity of their body fluid according to the surroundings.

Question 2.
How do organisms manage with stressful conditions existing in their habitats for short duration ? Explain with an example.
Answer:
Under such conditions

• The organisms move away from the stressful habitat to hospital area and returned to that area when it becomes normal state. eg: Siberian birds migrates to Bharatpur sanctuary in Rajasthan.
• The organisms under go hiberation if they can’t migrate
  eg: Polarbear.
• In higher plants seeds and some other vegetative reproductive structure serve as means to tide over stress conditions.

Question 3.
Explain different types of interspecific interactions
Answer:
(1) Beneficial interaction:-

• The interspecific interaction which is beneficial to both the species is called mutualism.
• Beneficial to one, but neutral to other.
• Commensalism

(2) Detrimental interaction:-

• Competition is the type of interaction that is detrimental to both the species.
• Parasitism- Beneficial to one and detrimental to the other.
• Amensatism – Detrimental to one and neutral to the other.

(3) Neutral interaction:- Commensalism is a type in which interaction is detrimental one and beneficial to the other.

Question 4.
Differentiate between ectoparasite and endoparasite.
Answer:

Ecto parasit	Endo parasite
Those organisms which live on the surface of the other living organism and derive food from it eg: lice on human	Those organisms which live inside the body of other living organism and derive food from it eg: Plasmodium and liver fluke in man.

Question 5.
What is brood parasitism? Give an example what adaptation has evolved in this phenomenon
Answer:
Brood parasitism is a phenomenon in which one species (parasite) lays eggs in the nest of other species (host) of bird and lets the host incubate them, eg: Cuckoo lays eggs in crow’s nest Cuckoo’s eggs shows resemblance with the eggs of crow in colour size etc which failed to identify by the crow with their eggs.

Question 6.
Name and explain the kind of interaction in the following
(1) Algae and fungi in lichens
(2) Head louse and humans
(3) Hermit crab and sea anemone.
Answer:
(1) Algae and fungi in lichens:-

• This is an example of mutualism in which both are benefited
• Fungi provide protection and helps in absorbing water and minerals where as the algae prepare food for the fungus.

(2) Head louse and human: This is an example of ectoparasitism the parasite gets shelter as well as food from human’s head.

(3) Hermit crab and sea anemone:- This is an example of commensalism in which sea anemone gets benefit for moving to places rich in nutrients while the hermit crab neither benefitted nor harmed.

Question 7.

The above graph shows the organisms response to abiotic environmental factors. Name the categories of animals. Which show the pattern a, b, and c respectively and define each of them.
Answer:
(a) Conformers:
These are organisms which cannot maintain a constant internal environment but change the body temperature and osmolarity of their body fluids according to the external conditions.

(b) Regulators:
These organisms which maintain a relatively constant environment called homeostasis.

(c) Partial regulators:
These are organisms which have evolved the capacity to regulate the internal environment of the body to a limited range of external factors beyond which they become conformers.

Question 8.
Explain the following
(i) Predators are conducts of energy transfer
(ii) Predators are prudent in nature
Answer:
(i)

• A predator in a food chain feeds on the prey and obtains energy
• When the predator becomes a prey to another animal in the food chain, it transfers the energy obtained from ‘its’ prey.

(ii) If a predator is too efficient and overexploits the prey, the prey population becomes extinct. As a result predator will also become extinct due to the lack of food and hence predator are said to be prudent in nature.

Question 9.
The Mediterranean orched Ophrys employs a method called sexual deceit to get the flowers pollinated. Explain the phenomenon.
Answer:
In the flower of Ophrys, one petal resembles the female of a bee species in size, colour markings etc.

• The male bee perceives it as a female and pseudo copulates with it.
• During the process the pollengrains from the anthers become dusted on the body of bees. When this bee is attracted to another flower of this orchid species, the process is repeated and the pollengrains falls on the stigma hence pollination is achieved.

Question 10.
Mention any 4 adaptations seen is Xerophytic plants to cope up with water scarcity.
Answer:

• Xerophytes (Desert plants) have thick cuticle on their leaf surface.
• Leaves are absent or reduced to spines to prevent transpiration.
• Presence of sunken stomata to reduce water loss.
• The photo synthetic function is taken up by green flattened stems.

 

You can Download Chapter 6 Molecular Basis of Inheritance Questions and Answers, 2nd PUC Biology Question Bank with Answers, Karnataka State Board Solutions help you to revise complete Syllabus and score more marks in your examinations.

Karnataka 2nd PUC Biology Question Bank Chapter 6 Molecular Basis of Inheritance

2nd PUC Biology Molecular Basis of Inheritance Ncert Text Book Questions and Answers

Question 1.
Group the following as nitrogenous bases and nucleosides:
Adenine, Cytidine, Thymine, Guanosine, Uracil and Cytosine.
Answer:
Nitrogenous bases Adenine, Thymine, Uracil, Cytosine. NucleosidesCytidine, Guanosine.

Question 2.
If a double stranded DNA has 20 percent of cytosine, calculate the percent of adenine in the DNA.
Answer:

Question 3.
If the sequence of one strand of DNA is written as follows:
5ATGCATGCATGC ATGCATGCATGC ATGC-3′
Write down the sequence of complementary strand in 5’—>3’ direction.
Answer:
5′ – ATGCATGC ATGC ATGC ATGC ATGC ATGC – 3′ (In question)
complement 3′ – TACG TACG TACG TACG TACG TACG – 5′
complement in 5′ – 3′ direction 5′ – GCAT GCAT GCAT GCAT GCAT GCAT GC AT – 3′.

Question 4.
If coding strand in a transcription unit is written as follows:
5′-ATGCATGCATGCATGCATGCATGCATGC – 3′ Write down the sequence of m-RNA.
Answer:
m RNA carries same code as coding strand except T is replaced by U.
(Question) transcription strand 5′ – ATGC ATGC ATGC ATGC ATGC ATGC ATGC – 3′ m RNA → 5′ – AUGC AUGC AUGC AUGC AUGC AUGC AUGC – 3′.

Question 5.
Which property of DNA double helix led Watson and Crick to hypothesise semi-conservative mode of DNA replication? Explain.
Answer:
2 strands of DNA has complementary base pairs which run in opposite direction. Property was that during DNA replication one strand was conserved while the complementary is formed new.

Question 6.
Depending upon the chemical nature of the template (DNA or RNA) and the nature of nucleic acids synthesised from it (DNA or RNA), list the types of nucleic acid polymerases.
Answer:
DNA Template

• DNA polymerases for DNA replication.
• RNA polymerases for RNA synthesis or transcription

RNA Template

• RNA dependent RNA polymerases for synthesis of RNA is some RNA viruses.
• Reverse transcriptase to synthesize DNA over RNA template.

Question 7.
How did Hershey and Chase differentiate between DNA and protein in their experiment while proving that DNA is the genetic material?
Answer:
They raised 2 types of bacteriophages

• On radioactive phosphorous (³²P)
• On radioactive sulphur (³⁵S).

³⁵S gets into protein and ³²P into DNA When both bacteriophages infected bacteria differently and by shaking them, viral protein coat was separated

After raising these bacteria it was found that those infected with ³²P bacteriophage → radioactivity was found. But with ³⁵S → no radioactivity was found.

Question 8.
Differentiate between the followings:
(a) Repetitive DNA and Satellite DNA
Answer:

Repetitive DNA	Satellite DNA
(i) sequence of N2 bases present in more than 1 copy in a genome.	(i) part of DNA  having repeated short sequences of N2 bases
(ii) Repeated DNA sequence may or may not be present in text.	(ii) Repeated sequence occur in tandem
(iii) Variability may or may not be present	(ii) Variability occurs

(b) mRNA and tRNA
Answer:

m-RNA	t – RNA
(i) Large sized RNA with cap and tail. (ii) Carries codon information	(i)   Small sized with 3-4 loops and a limb (ii) Carries infor­mation for association of AA with anti Condon for incor­poration

(c) Template strand and Coding strand
Answer:

Template strand	Coding strand
(i) The strand of DNA which takes part in transcription.	(i) It does not takes part in transcription.

Question 9.
List two essential roles of ribosome during translation.
Answer:

• Provides sites for attachment of m-RNA and charged t – RNA for polypeptide synthesis.
• One of its r – RNA functions as peptidyl transferase for peptide bond formation.

Question 10.
In the medium where E. coli was growing, lactose was added, which induced the lac operon. Then, why does lac operon shut down some time after the addition of lactose in the medium?
Answer:
Due to decrease in lactose substrate concentration, lac operon shuts down as it is inducible operon.

Question 11.
Explain (in one or two lines) the function of the followings:

(a) Promoter
Answer:
It is a gene that lies near operator which functions as binding site structural genes if operator allows.

(b) tRNA
Answer:
Functions as adapter molecule that picks  up a particular amino – acid from cellular pool and takes same over A site, m – RNA for incorporation into polypeptide

(c) Exons
Answer:
Coding segments present in primary transcript which on splicing by snRNP’s get joined to form functional m-RNA.

Question 12.
Why is the Human Genome project called a mega project?
Answer:
Because it involves

• Sequencing of over 3 × 109 bp
• Identification of all genes and alleles in human genome and their function.
• Storage of data requires storage space equal to 3300 books 1000 pages, each page with 1000 letters.

Question 13.
What is DNA fingerprinting? Mention its applications.
Answer:
DNA fingerprinting is technique of determing similarity and dissimilarity of VNTR’s between 2 samples of DNA so as to bring out relationship if any VNTR’s are specific for each individual. They are derived from parents in 50: 50 ratio.
Applications

• Identification – of criminals
• Paternity and Maternity disputes.
• Migrations
• Human Lineage.

Question 14.
Briefly describe the following:
(a) Transcription
Answer:
Transcription – Formation of-RNA over template of DNA.

The snRNA formed has codon information similar to sense or coding strand of DNA with just U replacing T.

• The DNA strand which function as a template is template or anti-sense strand.
• Only one of the DNA strands is transcribed
• The main enzyme taking part in transcription is RNA polymerase.

(b) Polymorphism
Answer:
Polymorphism It is the occurrence of more than one form of genetic material
Types →

• Allelic polymorphism – multiple alleles in a gene. So it alters structure and function of protein formed.
• SNP or single nucleotide Polymorphism – Unique in every human being. Useful in locating specific alleles, disease associated sequences.
• RFLP or Restriction Fragment Length polymorphism – Different sized fragments are formed by cleavage with same enzyme most RFPL have no effect on phenotypes.

(c) Translation
Answer:
Translation (Biosynthesis of proteins) Coded genetic message brought by m – RNA from DNA is charged into polypeptide chain (proteins).

DNA transcription mRNA translation Proteins Materials required for translation are ribosomes, AA, t RNA’s, aninoacylt – RNA synthetase, m – RNA and same factors Step in Translation . Activation of Amino Acids → charging of t RNA→ Initiation → Elongation → Termination → Modification.

(d) Bioinformatics
Answer:
Science of handling, storing as databases, analysing, modelling and providing access to various aspects of biological information, especially molecules connected with genomies and proteomics
Applications

• Organisation of Biological Data
• Functional Genomics
• Proteomics, Pharmacogenomics
• Medical informatics, chemoinformatics
• Faster drey research.

2nd PUC Biology Molecular Basis of Inheritance Additional Questions and Answers

2nd PUC Biology Molecular Basis of Inheritance One Mark Questions

Question 1.
Expand the term DNA, RNA and tRNA.
Answer:
DNA – Deoxy ribonucleic acid RNA – Ribo nucleic acid tRNA – transfer – RNA

Question 2.
Define genetic code.
Answer:
Relationship between the sequence of nucleotides or bases on mRNA and the sequence of amino acids in the polypeptide.

Question 3.
What are Okazaki fragments?
Answer:
The small stretches of DNA formed due to the opposite running of DNA template at the time of replication is called Okazaki fragments.

Question 4.
What is codon?
Answer:
It is the triplet nitrogenous base sequence which code for one amino acid. It lies on the m- RNA.

Question 5.
What is anti codon?
Answer:
It in the triplet nitrogenous bases in the t-RNA complementary to an m-RNA codon. It identifies a particular codon on mRNA.

Question 6.
What is a translation?
Answer:
It is the process of the formation of protein directed by a m-RNA molecule.

Question 7.
Define Transcription?
Answer:
It is the process of the formation of m-RNA on a DNA template.

Question 8.
Name the enzyme that catalyses
(a) Replication of DNA and
(b) Formation of RNA. (CBSE 1995)
Answer:
(a) Topoisomerase.
(b) RNA polymerase.

Question 9.
What is the genetic material of tobacco mosaic virus (TMV)
Answer:
RNA.

Question 10.
Name the bond present between two adjacent nucleotides
Answer:
Phosphodiester bond.

Question 11.
Due to mistake during transcription, ATG forms UAG in m-RNA. What change would occur in polypeptide chain translated by this m-RNA? (Cbse 1996)
Answer:
UAG is a termination codon and so at point protein synthesis will get stopped.

Question 12.
Name three different non – sense codons.
Answer:
UAA, UAG and UGA.

Question 13.
If the base sequence of one strand of DNA is CAT TAG TAC GAC, what will be the base sequence
(a) Of complementary DNA strand, and
(b) Of its complementary RNA strand? (CBSE 1991)
Answer:
(a) GTA ATC ATG CTG
(b) GUA AUCAUGCUG.

Question 14.
Name the scientist who proposed one gene one enzyme hypothesis. (CBSE 1997)
Answer:
Beadle and Tatum.

Question 15.
Name the enzyme that joints the short pieces in the lagging strand during synthesis of DNA.
Answer:
DNA legase. (CBSE 1998)

Question 16.
In which direction 5′ – 3′ or 3′ -5′ are the new strands of DNA formed during replication ? (CBSE 1992, 2K)
Answer:
5′ – 3′ direction

Question 17.
Give the present-day representation of central dogma.
Answer:

Question 18.
State Chargaff s base complementary rule.
Answer:
The total molar amount of adenine in any specimen of DNA is always equal to that of thymine. In a given DNA A = T and G = C.

Question 19.
Define mutation
Answer:
It is an abrupt and distinct change in the structure of base pair. It is a discontinuous inheritable and sudden change in an organism.

Question 20.
What do you call the kind of mutation in which a single base is added to a base strand : (CBSE 2K)
Answer:
Frame shift mutation.

Question 21.
Sickle cell anaemia is caused due to abnormal haemoglobin. Which chain of haemoglobin is responsible for this disease?
Answer:
β – chain of haemoglobin

Question 22.
What do the triplets AUG and UGA respectively code for during proteins synthesis?
Answer:
AUG – Methionine UGA – Termination codon (Nonsense codon)

Question 23.
Name the technique used by Watson and Crick to propose the double-helical structure of DNA molecule?
Answer:

• X-ray crystallography
• X-ray diffraction method.

Question 24.
Who discovered nucleic acid DNA? What was it called them?
Answer:
Fredrich Meischer. It was called as nuclein.

Question 25.
(a) What is the length of the pitch of helix?
(b) What is the distance between 2 base pairs is a stand of DNA?
Answer:
(a) 3.4 nm
(b) 34 nm.

Question 26.
Why is the distance between the 2 nucleotide chains in a DNA maintained almost constant?
Answer:
The complementary base pairing between the 2 strands i.e. adenine and thymine (double bond) and Guanine and cytosine (triple bond) is responsible for the uniform distance between the 2 strands.

Question 27.
Name the process which occurs in virus where the formation of DNA occurs from RNA.
Answer:
Reverse transcription.

Question 28.
Name the components ‘a’ and ‘b’ in the nucleotides with a parent given below. (CBSE, Delhi 2008)
Answer:

Question 29.
What are histones?
Answer:
Histones are positively charges proteins found in association with DNA in eukaryotic cell.

Question 30.
Name 2 organisms where RNA as the genetic material.
Answer:
QB Bacteriophage, Tobacco mosaic virus.

Question 31.
Name the main enzyme involved in the replication of DNA.
Answer:
DNA dependent DNA polymerase enzyme.

Question 32.
Name the types of synthesis ‘a’ and ‘b’ occurring in the replication of DNA as shown below (CBSE 2008)
Answer:

• a – continuous synthesis
• b – discontinuous synthesis.

Question 33.
What is replication fork in DNA?
Answer:
During DNA replication the unwinding of DNA leads to the formation of ‘Y’ shaped structure to the 2 strands of DNA duplex. This is known as the replication fork.

Question 34.
Define a cistron
Answer:
A cistron is defined as the length of mRNA, that codes for a polypeptide.

Question 35.
What is meant by hnRNA?
Answer:
The hnRNA is the precursor of mRNA transcribed by RNA polymerase II in eukaryotic cells hn represents heteronuclear RNA.

Question 36.
When and at what end does the ‘tailing’ of hnRNA take place? (AI 2009)
Answer:
After splicing, tailing occurs at the 3′ end of hn RNA.

Question 37.
Why is hn RNA required to undergo splicing?
Answer:
Since hn RNA contain both the coding sequences (exon) and the non-coding sequences (introns), hn RNA has to undergo splicing for the removal of introns.

Question 38.
Who proposed the operon concept?
Answer:
Francois Jacob and Jacque Monod proposed the operon concept.

Question 39.
Name the induce of lac operon in E. Coli?
Answer:
Lactose.

Question 40.
Given below is a schematic representation of a lac operon in the absence of an inducer. Identify ‘a’ and ‘b’ in it
Answer:

a – Repressor
b – operator.

Question 41.
What term is given to a single base DNA differences?
Answer:
When the repressor binds to the operator, the operon is switched off and transcription is stopped.

Question 42.
Expand VNTR.
Answer:
Variable Number of Tandem Repeats.

Question 43.
Regulation of lac operon by repressor is referred to as negative why is it so?
Answer:
When the repressor binds to the operator, the operon is switched off and transcription is stopped.

Question 44.
Name 2 plants whose genome have been sequenced.
Answer:
Rice and Arabidopsis.

Question 45.
Define DNA polymorphism
Answer:
Inheritable mutations at high frequency in a population. It refers to the variation at genetic level.

Question 46.
Who discovered the techniques of DNA fingerprinting
Answer:
Alec Jeffreys.

Question 47.
What is a probe in DNA-finger printing?
Answer:
A probe is a short stretch of DNA, with the nucleotide sequence that is complementary to that of VNTR sequence.

Question 48.
Name the branch of science that HGP is closely associated with.
Answer:
Bioinformatics.

Question 49.
Given below is the sequence of steps of transcription in eukaryotic cell. Fill up the blank 1, 2, 3, 4 left in the sequence.
Answer:

Single nucleotide polymorphism (SNPS).
1 – RNA polymerase
2 – hn
3 – processed RNA
4 – tail.

Question 50.
Write any 3 unusual bases present in Yeast’s alanine tRNA with their sources.
(CBSE 2004)
Answer:
All tRNA have 2 unusual bases – dihydro uridine (derived from uracil) and pseudo uridine (from uraicl. The third common unusual base is hypoxanthine (from adenine).

2nd PUC Biology Molecular Basis of Inheritance Two Marks Questions

Question 1.
What are 5′ end, 3′ end of a polynucleotide chain?
Answer:

• The poly nucleotide chain has at one end a free phosphate at the 5′ end of the pentose sugar. Which is referred to as 5′ end.
• The other end of polynucleotide chain has a free. 3′ – OH group at the 3rd end of the pentose sugar which is referred to as 3′ end of polynucleotide chain.

Question 2.
Label the diagram 1, 2, 3, 4, 5, 6. (CBSE 2004)
Answer:

• 5′ end
• Ribosome binding site
• Start
• Stop signal
• Open reading frames (ORFs)
• 3′ end.

Question 3.
Name the components (parts) A and B of the transcription unit ‘given below.
Answer:

A – Promoter
B – Coding strand.

Question 4.
(a) Who first proposed semi-conservative mode of replication of DNA.
(b) Which organisms is used in this experiment?
(c) Name the techniques used
(d) What is the result of first, second and 3rd generation?
Answer:
(a) Watson and Crick (1953)

• Eschirisia Coli

(i) Use heavy isotope ¹⁵N instead of normal ¹⁴
(ii) Use of Cesium chloride based density gradient configuration with ethidium bromide as flarochrome.
(iii) First generation DNA is hybrid as with intermediate heaviness due to presence of both ¹⁴N and ¹⁵N strands. The parent generation is heaviest.
Second generation 50% light (¹⁴N/¹⁴N) and 50% intermediate heavy (¹⁴N/¹⁵N). Third generation75% light (¹⁴N/¹⁴N) and 25% of intermediate heaviness (¹⁴N/¹⁵N).          This is possible only if DNA is double stranded with semi conservative replication. (one parent strand and other new strand) UACGAG AGAUUUi

Question 5.

Study the messenger RNA segment given above which is complete to be translated into a polypeptide chain

• Write the codons and ‘a’ and ‘b’
• What do they code for?
• How is peptide bond formed between 2 amino acids in the ribosome (CBSE 2008)

Answer:
(i) a – AUG
b – UAA | UAG | UGA

(ii) AUG codes for methionine.
UAA/ UAG/ UGA is stop / nonsense codon.

(iii) Peptide bond is formed between -COOH group of P- site amino acid and NH₂ – group of A – site amino acid with the help of ribozine peptidyl transferase provided by ribosome.

Question 6.
State any one reason to explain why RNA virus mutate and evolve faster than other viruses.
Answer:
RNA is an unstable highly reactive molecule due to its single-stranded structure and exposure of its nitrogen bases. But DNA is stable, the molecule, as its, nitrogen bases are not exposed, became its double-helical nature.

Repressor binds to the operator region
(o)  and prevent RNA polymerase from transcribing the given.
Look at the figure above depicting lac operon in E-Coii.
(a) What could be a series of events when an inducer is present in the medium in which E. Coli is growing.
(b) Name the inducer.
Answer:
(a) When the inducer is present in the medium it is absorbed at first slowly into the bacterium. The inducer binds with the repressor attached to the operator gene the repressor leaves the operator gene and allows the RNA polymerase to pass from promotor to the structural genes for transcription or formation of a polycistronic mRNA.
(b) Lactose or galactoside.

Question 7.
Draw schematically a single polynucleotide strand (with at least three nucleotides)
Answer:

Question 8.
Differentiate between euchromatin and heterochromatin.
Answer:
Euchromation

• These are the regions where chromatin is loosely packed.
• Euchromation stains lighter
• This is transcriptionally more active.

Hetero chromatin

• These are the regions where chromatin is tightly packed
• Hetero chromatin stains darker
• This is transcriptionally less active or inert.

Question 9.
Write the functions of DNA polymerase.
Answer:

• DNA polymerase catalyses the polymerisation of nucleotides into a polynucleotide strand of DNA.
• It carries out proof reacting in prokaryotes; it moves back and removes any wrong bases added before polymerisation continues.

Question 10.
Compare the roles of the enzymes DNA polymerase and DNA ligase in the replication fork of DNA.
Answer:
DNA polymerases the nucleotides in the 5’ —> 3′ direction, as a continuous stretch on the template strand with 3′ —> 5′ polarity and short stretches on the template strand with 5′ —> 3′ polarity. —> DNA ligase joins the short stretches of DNA formed on the template strand with 5′-3′ polarity.

Question 11.
Write the differences between mono-cistronic and polycistronic mRNAs.
Answer:

Monocistromic mRNA	Polycistromic mRNA
(1) It is the mRNA that can code for only one polypeptide i.e. it has one cistron. (2) it is normally found in eukaryotic cell.	(1) It is the mRNA that can code for more than one polypeptide i.e. it has more than one cistron. (2) It is found in prokaryotic cell.

Question 12.
Differentiate between Exons and Introns.
Answer:
Exons (HOTS)

• They are the coding sequence of DNA/RNA transcript, that form parts of mRNA and code for different regions of the polypeptide.
• They are joined together during splicing to make the information continuous.

Introns

• Introns are non coding sequences of DNA/ RNA transcript that do not become part of mRNA.
• They are removed during splicing.

Question 13.
Genetic code is specific and nearly universal justify. (Delhi 2008)
Answer:
Since a codon codes only for a particular amino acid, genetic code is specific or unambiguous. A codon codes for one particular amino acid in all living, be it a bacterium or a human, hence it is universal.

Question 14.
Why is that transcription and translation can be coupled in prokaryotic cell but not in eukaryotic cells?
Answer:
(a) In prokaryotes, mRNA does not require any processing to become active

(b) Transcription and translation occur in the same compartment cytosol, as there is no well defined nuclear membrane. There for it can be coupled.

In eukaryotic m-RNA has to be processed (splicing) before it become active. Since RNA is synthesised inside the nucleus and translation occurs in the cytoplasm, coupling of transcription and translation is not possible.

Question 15.
Why is it essential that RNA binds to both an amino acid and an mRNA codon, during protein synthesis?
Answer:
(a) By binding an amino acid at its 3′ end the tRNA transports the amino acid to the site of protein synthesis.

(b) It binds to the codon on mRNA through hydrogen bonds with its anticodon as it is recognised by the codon of the amino acid it carries, it is to release the amino acid at the correct site for polypeptide elongation.

Question 16.
What is an operon? How does lactose act as an inducer in the lac operon? (Al 2008)
Answer:
All the genes controlling a metabolic pathway, collectively constitute an operon. Lactose binds to the repressor and inactivates it, and prevents it from binding to the operator. As a result, the RNA polymerase gets access to the promoter and transcription proceeds, ie., the operon is induced to function.

Question 17.
Explain VNTR as the basis of DNA finger printing.
Answer:

• Variable number of tandem repeats belong to the class of satellite DNA referred to as mini satellite.
• The number of repeats shows very high degree of polymorphism as a result the size of VNTR varies.
• After hybridisation of DNA sample with VNTR probe, an autoradiogram developed which gives many bands give the characteristic pattern of an individual DNA.

Question 18.
Give the applications of DNA fingerprinting?
Answer:

• To identify criminals in the forensic labs.
• To determine the biological parent in case of dispute.
• To verify whether an immigrant is really a close relative of the mentioned resident.
• To identify racial groups to rewrite the biological evolution.

Question 19.
How is nucleosome formed? Draw a diagram of the nucleosome.
Answer:

In eukaryotes, histones which are positively charged proteins, become organised as a unit of 8 molecules, called histone octamer. The negatively charged DNA is wraped around the positively charged histone octamer, to form the structure, called nucleosome.

Question 20.
What is meant by R – cells and S – cell with which Frederick Griffith carried out his experiments on Diplococcus pneumonial? What did he prove from these experiments?
Answer:
R – cells are those bacterial cells that form rough colonies, without a capsule and are non-virulent. S – cells are those cells, that form smooth colonies, with a capsule and are virulent. He proved that virulence of S – cells had some how been transferred into R – cells, which became transformed into S- cells, it is the genetic material that had effected transformation.

Question 21.
Draw the schematic representation to show continuous or discontinuous synthesis of DNA (replication of DNA) and label it.
Answer:

Question 22.
Explain frames shift mutation.
Answer:
(a) It is the type of mutation where insertion or deletion of one or two bases changes the reacting frame from the point of insertion or deletion.

(b) When three or multiples of three bases are added there is addition of one or more amino acids and the reacting of the frame remains unaltered after that. This provides the genetic proof that codons are triplets.

Question 23.
A t-RNA is charged with the amino acid phenylalanine.
(a) At what end of the tRNA is the amino acid attached ?
(b) Give the mRNA codon that codes for phenylalanine.
(c) Which enzyme is responsible for this attachment ?
Answer:
(a) Amino acid is attached to the 3′ end of t-RNA.
(b) UUC or UUU are the codes for phenylalanine.
(c) Amino Acyl tRNA synthetase enzyme is responsible for this attachment.

Question 24.
(a) Draw the schematic diagram of tRNA showing the following.
(i) Methionine attached to the amino acid accept site.
(ii) Correct base sequence at the anticodon loop
(b) Write the role of “untranslated regions” on mRNA segment play in protein synthesis?
Answer:
(a)

(b) They are needed for efficient translation

Question 25.
Draw a labelled diagram depiciting schematically the process of elongation in translation
Answer:

Question 26.
Describe the goals of Human genoine project.
Answer:
The major goals of Human genome project are

• Determine the sequence of the 3 billion base pairs present in Human DNA.
• Identify the genes in the human DNA.
• Store the information in data bases.
• Improve the tool for data analyses.
• Address ELSI (ethical, leagal, social issues) that arise from project.
• Transfer the technologies to other sectors.

2nd PUC Biology Molecular Basis of Inheritance Five Marks Questions

Question 1.
Describe the features of double helical model of DNA.
Answer:
The features of double helical DNA are

• It is made up of 2 polynucleotide of sugar phosphate and the nitrogen bases inside.
• The two chains have antiparallel polarity ie., one has 5′ —> 3’ polarity and the other with 3′ —> 5′ polarity.
• The bases of 2 strands are joined by double hydrogen bond between adenine and thymine and triple hydrogen bond between guanine cytosine.
• The distance between 2 base pairs is 0.34nm and the distance between each turn is 3.4nm. Each turn consists of 10 base pairs.
• The plane of one base pair stacks over the other in double helen this gives the stability of double helical structure.

Question 2.
(1) Represent diagramatically the Watson Crick model for semi conservation replication of DNA.
(2) Differentiate between continuous and discontinuous synthesis of DNA.
Answer:

(2)

Continuous	Discontinuous
(a) One stand of DNA is synthesised as a continuous strech in the 5′ —>3′ direction.	(a) Short stretches  are synthesised in the 5’—>3′ direction from replication fork
(b) The template strand of DNA strand is with 3’—>5′ polarity.	(b) The DNA strand with 5′ —> 3′ polarity is the template strand  for this.
(c) No need of enzyme ligase (for joining)	(c) DNA ligase  enzyme is required  for joining short stretches.
(d) There is no need for primers.	(d) There is need for primers.

Question 3.
Write short notes on different types of RNAs.
Answer:
The RNAs are of 3 types

• Messenger RNA (m – RNA)
• Transfer RNA (t – RNA)
• Ribosomal RNA (r – RNA)

m – RNA It provides the template for polypeptide synthesis, ie., it decides the sequence of amino acids in the polypeptide through the sequence of bases on it. t – RNA It has the shape of clover leaf in two dimensional structure It transports the amino acids to the site of protein synthesis it recognises the codon on m RNA. r – RNA It plays the structural and catalytic role during translation.

Question 4.
Define genetic code and write its salient features.
Answer:
Genetic code is the relationship between the sequence of nucleotides on mRNA and sequence of amino acids in the polypeptide.
Its features are

• The genetic code is universal ie., the codons code for one amino acid is same in all organism.
• Codons are triplet codons and there are 64 codons. 61 codons code for twenty different amino acids while the other three (UAA, UAG, UGA) are termination codons which do not code for any amino acids.
• Each codon codes for only one particular amino acid. Therefore it is unambiguous.
• Some amino acids are coded by more than one codon there for it is said to be degenerate.
• The codons are read in a continuous manner, without any punctuation ie., codons are comma less.
• AUG has dual functions of coding for metheonine as well as functioning as initiation codon.

Question 5.
(1) Represent schematically the process of transcription in eukaryotic cells.
(2) How does DNA polymerase function in the replication fork of DNA?
Answer:

(2) The DNA polymerase can catalase the polymerisation of nucleotides only in one direction is 5′ —> 3′ direction.
On the template stand with 3’—>5′ polarity the polymerisation occurs continuously and on the template strand with 5′ —> 3′ polarity, polymerisation occurs in short stretches (discontinuous synthesis).

Question 6.
(a) Explain with the help of schematic representation, the lac operon in E-Coli.
(b) Mention the role of lactose in this operon.
Answer:
(a) Jacob and Monod explained that lactose inducer the expression of genes leading to its catabolism.

(b) Role of lactose

• Lactose is a substrate for the enzyme (3- galactosidase.
• It function as the inducer and regulates the switching on and off of the operon.
• When lactose is present, it combines with the repressor protein which otherwise has a high affinity for the operator.
• This inactivates the repressor from binding to the operator and hence transcription continuous ie., the operon is switched on.