KSEEB SSLC Class 10 Science Important Questions and Answers<\/a>\u00a0helps you to revise the complete Karnataka State Board Syllabus and score more marks in your examinations.<\/p>\nKarnataka SSLC Class 10 Science Important Questions Chapter 8 How do Organisms Reproduce?<\/h2>\n
Question 1.
\nDefine reproduction.
\nAnswer:
\nThe biological process by which organisms produce young ones, which resemble themselves, is known as reproduction.<\/p>\n
<\/p>\n
Question 2.
\nExplain the importance of reproduction in organisms.
\nAnswer:
\nReproduction is an important characteristic feature of living organisms. It is an essential life process, which not only helps in survival of the species but also helps in continuity of that race and group. Young ones replace the old and dying ones. These young ones feed, grow and reproduce again.<\/p>\n
Reproduction also helps in increasing the population of the species. Reproduction acts as a vehicle of organic evolution by transmitting advantageous variations to the offspring. In the absence of reproduction, species would perish and life on earth would be wiped out of existence.<\/p>\n
Question 3.
\nHow are the modes for reproduction different in unicellular and multicellular organisms?
\nAnswer:
\nUnicellular organisms generally reproduce asexually by fission, budding or spore formation. Their body has just one cell, which can easily multiply by simple cell division, budding or spore formation.<\/p>\n
Such methods are difficult in multicellular organisms as they have a complex organization of specialized tissues. Therefore, multicellular organisms usually reproduce by sexual method.<\/p>\n
Question 4.
\nHow does reproduction help in providing stability to populations of species?
\nAnswer:
\nPopulation of any species will remain stable when the birth rate is equal to the death rate. Reproduction produces new individuals, which will compensate for the deaths. Thus reproduction provides stability to population of a given species.<\/p>\n
Question 5.
\nIs reproduction essential for the survival of the individual?
\nAnswer:
\nNo, reproduction is not essential for the survival of the individual. An organism incapable of reproduction will also survive and complete its life cycle. However, reproduction is most essential for the growth in population and survival of the species. In the absence of reproduction, species will be wiped out of existence.<\/p>\n
Question 6.
\nWhy do organisms of the same species look similar?
\nAnswer:
\nReproducing organisms create new individuals similar to themselves. The individuals of the same species are the products that emerge from a common but similar blueprint. The DNA of the parents decides the blueprint. During reproduction, similar copies of the blueprint are produced by a process called DNA copying or DNA replication.<\/p>\n
Question 7.
\nWhat is variation? Why are hereditary variations important?
\nAnswer:
\nThe young ones of any species may resemble their parents broadly but differ from them in many ways. The differences in the characters among the offspring compared to their parents is called variation. Variation is necessary for organic evolution.<\/p>\n
<\/p>\n
Question 8.
\nWhat is DNA? What is its structure called? Where is it located in the cell?
\nAnswer:
\nDNA stands for Deoxyribo Nucleic Acid. It is a macromolecule found in chromosomes of living beings and carries the genetic information of the organism. The structure of DNA is called \u2018double helix\u2019 structure.<\/p>\n
Every eukaryotic cell has a nucleus, which contains chromosomes. These chromosomes carry information for the inheritance of characteristics from the parents to their offspring in the form of DNA molecules.<\/p>\n
Question 9.
\nWhat is meant by DNA copying? What is its importance?
\nAnswer:
\nThe process of producing two identical copies of one original DNA molecule is called DNA copying. It is also called DNA replication. DNA replication is important because replication is needed during cell division. Replication allows the cell to be duplicated so that it can continue the process of cell division.<\/p>\n
DNA copying enables organisms to beget young ones similar to their own kind. The process of DNA copying brings some variation each time. The surviving cells are similar to but subtly different from each other. This inbuilt tendency for variation during reproduction brings variations among individuals of the same species. This is useful for ensuring survival of the species.<\/p>\n
Question 10.
\nWhy is DNA copying an essential part of the process of reproduction?<\/p>\n
OR<\/p>\n
What is the importance of DNA copying in reproduction?<\/p>\n
Answer:
\nThe process of reproduction produces offspring similar to the parents. The exact blueprint of the body is inherited by the offspring due to DNA copying in the parent cell. This is why DNA copying is an essential part of reproduction.<\/p>\n
Question 11.
\nBriefly describe the process of DNA copying.
\nAnswer:
\nThe replication of DNA occurs in every cell during cell division. The process requires the uncoiling of the two strands of the DNA helix. The two open strands serve as templates for the assembly of daughter strands. The assembly of new strands takes place in a complimentary mode.<\/p>\n
This process is accompanied by the creation of an additional cellular apparatus. Then, the two DNA copies separate out each having its own cellular apparatus. Effectively, a cell divides to give rise to two cells.<\/p>\n
Question 12.
\nWhy is variation beneficial to the species but not necessarily for the individual?
\nAnswer:
\nPopulations of organisms reside in well-defined places or niches in the ecosystem. However, habitats or niches can change because of reasons beyond the control of the organisms. Variations allow organisms to exist in diverse habitats or niches. In the absence of variations, a species may be restricted to a particular area.<\/p>\n
If this area gets drastically altered, due to various natural or human-made causes, the species may be wiped out. However, if some variations were present in a few individuals, they could colonize other habitats, reproduce and could survive. But if variations were present in a single organism there would be very little chance for it to survive. Therefore, variation is beneficial to the species but not necessarily for the individual.<\/p>\n
Question 13.
\nMention the major modes of reproduction seen in animals.
\nAnswer:
\nReproduction in animals takes place principally by two modes. They are asexual reproduction and sexual reproduction.<\/p>\n
Question 14.
\nWhat is asexual reproduction?
\nAnswer:
\nA type of reproduction in which the young one arises from a single parent and is genetically identical to the parent is called asexual reproduction. This process does not involve the fusion of gametes.<\/p>\n
Question 15.
\nGive examples of animals that reproduce by asexual method.
\nAnswer:
\nLower order organisms like amoeba, yeast and hydra reproduce by asexual method.<\/p>\n
Question 16.
\nWhat is the method of reproduction in amoeba?
\nAnswer:
\nAmoeba is a unicellular organism. It reproduces asexually by the method of binary fission.<\/p>\n
<\/p>\n
Question 17.
\nWhat is binary fission in reproduction? Name an organism that reproduces by this method.
\nAnswer:
\nA kind of asexual reproduction in which a unicellular parent cell divides itself into two daughter cells is known as binary fission. Amoeba reproduces by binary fission.<\/p>\n
question 18.
\nExplain the process of reproduction in amoeba.
\nAnswer:
\n
\nAmoeba is a unicellular eukaryotic organism. Its body is made of a single cell. It reproduces asexually by the method of binary fission. The adult amoeba becomes ready for binary fission. First the nucleus divides into two. A constriction develops dividing the cytoplasm into two parts.<\/p>\n
The parent cell breaks at the point of constriction resulting in two daughter amoebae, which are identical to that of the parent. This is a form of asexual reproduction called binary fission.<\/p>\n
Question 19.
\nWhat is multiple fission in reproduction? When does amoeba reproduce by multiple fission?
\nAnswer:
\nA type of asexual reproduction in which a unicellular organism divides itself into three or more daughter cells that are identical to the parent organism is called multiple fission. Amoeba reproduces by the method of multiple fission under unfavourable or drought conditions to increase the chances of survival of daughter cells.<\/p>\n
Question 20.
\nHow does binary fission differ from multiple fission?
\nAnswer:
\nBinary fission is a mode of asexual reproduction in which a unicellular parent organism divides itself into two daughter organisms through the process of cell division. This method produces two young ones. This happens under favourable conditions in the absence of any stress.<\/p>\n
Multiple fission is a mode of asexual reproduction in which a unicellular parent organism undergoes cell division to produce more than two (many) young ones. This type of reproduction occurs under unfavourable or stressful conditions.<\/p>\n
Question 21.
\nExplain binary fission in Leishmania.
\nAnswer:
\nIn Leishmania, binary fission occurs in a definite orientation in relation to flagella. Splitting of parent cell during fission takes place in a definite plane (longitudinally) with respect to flagellum at its ends.
\n<\/p>\n
Question 22.
\nName the disease caused-by Leishmania.
\nAnswer:
\nThe disease kala-azar is caused by Leishmania.<\/p>\n
Question 23.
\nWhat is the difference between binary fission in amoeba and leishmania?
\nAnswer:
\nIn amoeba, the splitting of the two cells during division can take place in any plane. Binary fission in Leishmania happens in a longitudinal plane.<\/p>\n
Question 24.
\nWhat is the mode of reproduction in yeast? Explain briefly.
\nAnswer:
\nYeast reproduces asexually by a process known as budding. The parent yeast cell forms a small bud on its own body, which eventually develops into a new individual. On maturity, the bud breaks away from the parent body and gets independent existence.<\/p>\n
Question 25.
\nDescribe a simple activity to show the reproduction in yeast cells.
\nAnswer:
\nYeasts reproduce asexually by budding. This can be observed under a powerful microscope. Dissolve about 10 g of sugar in 100 mL of water. Take 20 mL of this solution in a test tube and add a pinch of yeast granules to it. Put a cotton plug on the mouth of the test tube and keep it in a warm place.<\/p>\n
After 1 or 2 hours, put a small drop of yeast culture from the test tube on a slide and cover it with a cover slip. Observe the slide under a microscope. Now we see many yeast cells and some of them show budding on the outside wall of their cell wall.<\/p>\n
Question 26.
\nHow do fungi reproduce?
\nAnswer:
\nFungi reproduce asexually by the method of spore formation. Spore formation is a method of asexual reproduction in which the parent plant produces hundreds of tiny spores, which can grow into new organisms under favourable conditions.<\/p>\n
Question 27.
\nDescribe how growth of fungus on a piece of moist slice of bread takes place.
\nAnswer:
\nTake a slice of moistened bread. Keep it on a plate in a cool, moist and dark place. Observe the surface of the slice with a magnifying glass for over a week. A white cottony mass appears on the surface of the bread which gradually turns black. This is due to the growth of bread mould (a fungus). The spores of fungus will always be hanging in air.<\/p>\n
They settle on the moist bread which provides favourable conditions for their germination. The cottony growth on the bread is a mass of vegetative filaments of the fungus. These filaments develop asexual sporangia which are black in colour. This is why the cottony mass turns black after a couple of days.<\/p>\n
Question 28.
\nHow will an organism be benefited if it reproduces through spores?
\nAnswer:
\nThe following are some benefits for the organism that reproduces through spore formation:<\/p>\n
\n- Reproduction through spores is simple as well as faster.<\/li>\n
- The spores are light in weight, thus keep floating in the air. This helps in their dispersal.<\/li>\n
- The spores are covered with a thick layer, which enables them to remain dormant in unfavourable conditions.<\/li>\n<\/ul>\n
Question 29.
\nWhat is fragmentation? Name an organism that reproduces by this method.
\nAnswer:
\nFragmentation is a form of asexual reproduction wherein a parent organism breaks into fragments and each fragment is capable of growing independently into a new organism. Spirogyra is a filamentous alga. It reproduces by the method of fragmentation.<\/p>\n
<\/p>\n
Question 30.
\nWhy do most of the multicellular organisms need more complex methods of reproduction?
\nAnswer:
\nMulticellular organisms cannot simply divide cell-by-cell or regenerate from its fragments. This is because, many multicellular organisms are not simply a random collection of cells. They have many different specialised cells, which are organised into tissues, and tissues are organised into organs designed to carry out varied but different activities.<\/p>\n
These organs are placed at definite positions in their body. In such a carefully organised situation, cell-by-cell division or regeneration of fragments would be impractical. Therefore, multicellular organisms need to use more complex ways of reproduction.<\/p>\n
Question 31.
\nWhat is regeneration? Name an organism that reproduces by this method.
\nAnswer:
\nRegeneration is a type of asexual reproduction in which the organism has the ability to give rise to new individual organisms from their body parts. This method of asexual reproduction is found in animals like planaria, earthworm, starfish etc.<\/p>\n
Question 32.
\nWith the help of a suitable diagram explain asexual reproduction in planaria.
\nAnswer:
\n
\nPlanaria reproduces asexually by the method of regeneration. In this mode of reproduction, planaria simply constricts its body until it actually separates into two parts. One part is the anterior end and the other is the posterior end. Each of the parts then regenerates the missing portion and thus two complete individuals arise.<\/p>\n
Even if planaria is cut into a number of pieces, each piece grows into a complete organism by regeneration. Specialised cells carry out regeneration. These cells proliferate and make large numbers of cells. From this mass of cells, different cells undergo changes to become various cell types and tissues. These changes take place in an organised sequence.<\/p>\n
Question 33.
\nDifferentiate between regeneration and fragmentation.
\nAnswer:
\nRegeneration:<\/p>\n
\n- This type of reproduction is seen in fully differentiated organisms.<\/li>\n
- It is carried out by specialized cells.<\/li>\n
- Specialized cells proliferate to form a mass of cells from which various cell types and tissues emerge.<\/li>\n<\/ol>\n
Fragmentation:<\/p>\n
\n- This type of reproduction is seen in organisms with simple body organization.<\/li>\n
- No specialized cells are involved in this process.<\/li>\n
- The parent body breaks into segments and each segment develops into a new organism<\/li>\n<\/ol>\n
Question 34.
\nWith the help of a suitable diagram explain the method of reproduction in hydra.
\n
\nAnswer:
\nHydra is a multicellular organism. It reproduces asexually by the method of budding. First, a small outgrowth called \u2018bud\u2019 is formed on the side of its body by the repeated mitotic divisions of its regenerative cells.<\/p>\n
The bud grows gradually to form a small hydra. The young hydra develops a mouth and tentacles. Finally the tiny hydra detaches itself from the body of parent and lives as a separate organism. This method of asexual reproduction is called budding.<\/p>\n
<\/p>\n
Question 35.
\nCan you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?
\nAnswer:
\nMulticellular organisms are not mass of random collection of similar cells. They consist of many different types of specialised cells, which are organized into tissues and tissues are organised into organs. These organs with different cell structures are located in specific positions of the body.<\/p>\n
Regeneration happens through mitosis and a particular type of tissue can give rise to its own kind only. Hence, regenerating a different kind of tissue from another kind is not possible. Therefore, complex organisms cannot give rise to new individuals through regeneration.<\/p>\n
Question 36.
\nWhat is the reproductive method in Leishmania, plasmodium and yeast?
\nAnswer:
\nLeishmania, plasmodium and yeast reproduce by asexual methods. Leishmania reproduces by the method of binary fission. Plasmodium reproduces by multiple fission. Yeast reproduces by the method of budding.<\/p>\n
Question 37.
\nWhat is vegetative propagation? Name some plants that are multiplied by this method.
\nAnswer:
\nA form of asexual reproduction in plants, in which new plants grow from the vegetative parts, such as leaves, stem or roots, is called vegetative propagation. New plants of sugarcane, roses, grapes, banana, jasmine, rose etc., are grown by vegetative propagation.<\/p>\n
Question 38.
\nWhy is vegetative propagation considered as asexual reproduction?
\nAnswer:
\nIn vegetative propagation only one parent is involved and the offspring is genetically identical to the parent. This mode of reproduction does not involve the fusion of gametes. Therefore, vegetative propagation is considered as asexual reproduction.<\/p>\n
Question 39.
\nWhy is vegetative propagation practiced for growing some types of plants?
\nAnswer:
\nSome plants do not produce seeds or they produce seeds from which a new plant cannot be grown. Vegetative propagation is practiced for growing such type of plants.<\/p>\n
Question 40.
\nGive examples of three plants that have lost the ability to bear seeds.
\nAnswer:
\nExamples of plants that have lost the ability to bear seeds include plantain, rose and jasmine.<\/p>\n
Question 41.
\nList the advantages of vegetative propagation.
\nAnswer:
\nThe following are the advantages of vegetative propagation<\/p>\n
\n- The new plant is genetically a replica of the parent plant. Therefore, purity of the variety is maintained in vegetative propagation.<\/li>\n
- In this method, it is possible to propagate those plants that are not able to produce seeds.<\/li>\n
- New plants can be grown quickly by vegetative propagation. Plants raised by this method can bear flowers and fruits earlier than those produced by seeds.<\/li>\n<\/ol>\n
Question 42.
\nHow do you show vegetative propagation in potato?
\nAnswer:
\nPotato is modified stem and therefore it is a vegetative part of the plant. Take a potato and cut it into small pieces such that some pieces contain a notch or bud and some do not. Spread some cotton on a tray and wet it. Place the potato pieces that contain notch and other pieces separately on the wet cotton.<\/p>\n
Ensure that the cotton is kept moist all the time. Observe the changes taking place in the potato pieces over the next few days. It is observed that the potato pieces with notch will develop fresh green shoots and roots from the sites of notches.<\/p>\n
Pieces of potato that have no notches do not develop shoots and roots. This shows that a new potato plant can be grown from a potato piece that has notches. This demonstrates vegetative propagation in potato.<\/p>\n
<\/p>\n
Question 43.
\nHow does a bryophyllum plant reproduce?
\nAnswer:
\n
\nBryophyllum reproduces by vegetative propagation. There are notches along the leaf margin of bryophyllum. When a leaf of this plant falls into the soil, buds emerge from these notches and develop into new plants.<\/p>\n
Question 44.
\nHow does a money plant propagate itself?
\nAnswer:
\nA money plant propagates vegetatively from its stem.<\/p>\n
Question 45.
\nHow does rhizopus reproduce? Explain.
\nAnswer:
\nRhizopus is a fungus. It reproduces asexually by spore formation. Rhizopus is a filamentous alga. The thread-like body structure of this organism is called hyphae. Each hyphae has a tiny blob called sporangia at its free end. These blobs contain \u2018seeds\u2019 of reproduction called spores.<\/p>\n
Sporangia break and release spores to the surrounding medium. The spores are covered by thick walls that protect them until they get favourable conditions. When these spores come into contact with a moist surface, they begin to grow new filaments.
\n<\/p>\n
Question 46.
\nWhat are the reproductive structures in rhizopus called?
\nAnswer:
\nThe reproductive structures in rhizopus are called sporangia. These are blob-like structures that contain spores.<\/p>\n
Question 47.
\nWhat is sexual reproduction?
\nAnswer:
\nA type of reproduction, which involves the fusion of male and female gametes, is known as sexual reproduction.<\/p>\n
Question 48.
\nWhat are the advantages of sexual reproduction?
\nAnswer:
\nSexual reproduction promotes genetic variability, favours the development of adaptive features, and speeds up evolution.<\/p>\n
Question 49.
\nWhat is meiosis? What is its need?
\nAnswer:
\nA type of cell division that results in daughter cells with half the number of chromosomes of the parent cell is called meiosis. Meiosis is required for producing reproductive cells such as gametes. Sexual reproduction allows for the production of unique offspring of the species with variable traits.<\/p>\n
This becomes possible because the genetic material from two parents gets mixed and produces a unique combination. This requires that the daughter cells produced by cell division must contain only half the chromosomes present in the parent cell.<\/p>\n
When this happens, the zygote can again become diploid and have the same number of chromosomes as the parent cell. Therefore, meiosis is necessary for sexual reproduction.<\/p>\n
<\/p>\n
Question 50.
\nWhat are the advantaees of sexual reproduction over asexual reproduction?
\nAnswer:
\nSexual reproduction involves the fusion of male and female gametes and usually involves two parents. Since the characteristics are inherited from both the mother and the father, the offspring shows variation in characteristics. This is useful in adaptation and survival. The offspring in asexual reproduction are genetically identical to the parent and hence no variation is possible.<\/p>\n
Question 51.
\nDistinguish between sexual reproduction and asexual reproduction.
\nAnswer:
\nSexual reproduction:<\/p>\n
\n- Involves the fusion of gametes.<\/li>\n
- Usually two parents are involved.<\/li>\n
- The offspring is unique.<\/li>\n
- The offspring is genetically different from the parents.<\/li>\n
- Produces genetic variations in characteristics.<\/li>\n
- One or more offspring are produced<\/li>\n<\/ol>\n
Asexual reproduction:<\/p>\n
\n- Does not involve the fusion of gametes.<\/li>\n
- Only one parent is involved.<\/li>\n
- The offspring is a copy of the parent.<\/li>\n
- The offspring is genetically identical to the parent.<\/li>\n
- Does not produce any genetic variations in characteristics.<\/li>\n
- Two or more offspring are produced.<\/li>\n<\/ol>\n
Question 52.
\nWhat are gametes? What are its types?
\nAnswer:
\nSpecialized cells, which are directly involved in the process of reproduction in higher order plants and animals, are called gametes. They are als called sex cells or germ cells. There are two types of gametes: Male gamete and female gamete. The male gamete is called sperm and the female gamete is called ovum (also called egg).<\/p>\n
Question 53.
\nWhat is fertilization ?
\nAnswer:
\nThe fusion of a male sex cell and a female sex cell resulting in a single cell, which develops into a new organism, is called fertilization.<\/p>\n
Question 54.
\nGive the meaning of the following terms: Gamete, gonads, sperm, ovum, fertilization, and zygote.
\nAnswer:<\/p>\n
\n- Gamete: The cells involved in sexual reproduction are called gametes.<\/li>\n
- Gonads: The reproductive glands that produce sex cells are called gonads.<\/li>\n
- Sperm: The male sex cell (male gamete) is called sperm.<\/li>\n
- Ovum: The female sex cell (female gamete) is called ovum or egg.<\/li>\n
- Fertilization: The fusion of sperm and ovum resulting in a single cell is called fertilization.<\/li>\n
- Zygote: A fertilized ovum is called zygote.<\/li>\n<\/ul>\n
Question 55.
\nName the sex cell produced in female reproductive system and the sex cell produced in male reproductive system.
\nAnswer:
\nThe sex cell produced in female reproductive system is called egg or ovum. The sex cell produced in male reproductive system is called sperm.<\/p>\n
Question 56.
\nDistinguish between male gamete and female gamete.
\nAnswer:
\nMale gamete:<\/p>\n
\n- Male gamete is produced in the male reproductive system.<\/li>\n
- The male gamete in animals is called sperm.<\/li>\n
- Male gamete is usually motile and small in size.<\/li>\n
- Generally male gamete does not store food.<\/li>\n<\/ol>\n
Female gamete:<\/p>\n
\n- Female gamete is produced in the female reproductive system.<\/li>\n
- Female gamete is called egg or ovum.<\/li>\n
- Female gamete is non-motile and usually bigger in size.<\/li>\n
- Female gamete generally stores food.<\/li>\n<\/ol>\n
Question 57.
\nIn which group of green plants do we find sexual mode of reproduction?
\nAnswer:
\nWe find sexual mode of reproduction in flowering plants, which are also known as angiosperms.<\/p>\n
Question 58.
\nWhat are angiosperms? Name the organ of reproduction in angiosperms.
\nAnswer:
\nPlants that bear seeds that are enclosed in fruit are called angiosperms. These are also known as flowering plants. The organ of reproduction in angiosperms is flower.<\/p>\n
<\/p>\n
Question 59.
\nDraw a labelled diagram of the loneitudinal section of a flower.
\nAnswer:
\n<\/p>\n
\n- Pistil – Female reproductive part<\/li>\n
- Stigma – Terminal part of pistil; the part that receives pollen<\/li>\n
- Style – Middle elongated part of pistil; the connective tissue between stigma and ovary<\/li>\n
- Ovary – Bottom part of pistil; the part that contains ovules<\/li>\n
- Stamen – Male reproductive part; the part that produces pollen grains<\/li>\n
- Anther – Pollen-producing organs<\/li>\n
- Filament – Stalk supporting anthers .<\/li>\n
- Petals – Collectively called corolla<\/li>\n
- Sepals – Collectively called calyx; protective leaf-like enclosures for the flower buds<\/li>\n
- Stamen (Male) – Anther, Filament<\/li>\n
- Pistil or carpel (Female) – Stigma, Style, Ovary<\/li>\n<\/ul>\n
Question 60.
\nWhich are the four prominent parts (whorls) present in a typical flower?
\nAnswer:
\nThe four prominent parts in a typical flower are sepals, petals, stamens and carpels.<\/p>\n
Question 61.
\nWhat is a sepal? What is its function?
\nAnswer:
\nThe outermost whorl of a flower consisting of green coloured units is called sepal. The sepals protect the flower, especially in the bud condition.<\/p>\n
Question 62.
\nWhat are petals? What is its function?
\nAnswer:
\nAs we move from outside towards inside of a flower, the second whorl consists of bright coloured segments called petals. Petals are modified leaves that surround the reproductive parts of flowers. Together, all of the petals of a flower are called a corolla. Petals protect the reproductive parts that lie inside the flower. Their function is to attract insects for pollination.<\/p>\n
Question 63.
\nWhat are stamens ? What is their function?
\nAnswer:
\nTheThe male reproductive structures in a flower are called stamens. The chief function of stamens is to produce pollen grains, which produce male sex cells.<\/p>\n
Question 64.
\nWhat are carpels? What is each carpel made of? What is their function?
\nAnswer:
\nThe female reproductive structures in a flower are called carpels. Each carpel consists of an ovary, which contains one or more ovules, a style and the stigma. A carpel in a flower consists of ovary, style and stigma.<\/p>\n
The ovary of a carpel produces ovules. The ovule produces female sex cells. The ovary protects the ovule. After fertilisation, the ovule will become the fruit. The style of a carpel is a tubular structure between the stigma and the ovary.<\/p>\n
The style helps the movement of pollens from the stigma to the ovary. Stigma is the receptacle for pollen. It has a sticky surface so that pollens stick. The stigma also transports the pollen to the ovum for fertilization.<\/p>\n
<\/p>\n
Question 65.
\nDescribe briefly the structure of a carpel.
\nAnswer:
\nEach carpel consists of an ovary, which contains one or more ovules, a style and the stigma. The ovary is at the base of the flower. A tubular structure that extends from the ovary is called the style. The top of the style is a surface called stigma, which receives pollens.<\/p>\n
Question 66.
\nName the structure that gives rise to and contains the female reproductive cells in a flower. Where is it located?
\nAnswer:
\nThe structure that gives rise to and contains the female reproductive cells in a flower is called ovule. It is located inside the ovary.<\/p>\n
Question 67.
\nWhich are the male and female reproductive parts in a flower?
\nAnswer:
\nStamens and carpels are the reproductive parts in a flower. Stamen is the male reproductive part and carpel is the female reproductive part in a flower.<\/p>\n
Question 68.
\nWhat are unisexual flowers? Give two examples.
\nAnswer:
\nFlowers, which contain either stamen or carpel, are called unisexual flowers. Such flowers will have to undergo only cross-pollination. For example, flowers of papaya and watermelon are unisexual.<\/p>\n
Question 69.
\nWhat are bisexual flowers? Give two examples.
\nAnswer:
\nFlowers that contain both stamen and carpel are called bisexual flowers. Such flowers can undergo both self-pollination and cross-pollination. Example: Mustard, hibiscus, etc.<\/p>\n
Question 70.
\nWhich are the two major steps involved in reproduction in angiosperms?
\nAnswer:
\nAngiosperms reproduce by sexual method. Reproduction in angiosperms involves two steps namely pollination and fertilization.<\/p>\n
Question 71.
\nWhat are pollen grains? What do pollen grains contain?
\nAnswer:
\nA fine powdery substance, typically consisting of microscopic yellow grains discharged from the stamen of a flower is called pollen grain. Each grain of pollen contains a male gamete that can fertilize the egg.<\/p>\n
Question 72.
\nWhat is pollination ? Mention its importance in reproduction.
\nAnswer:
\nThe transfer of pollen from the anther of a flower to the stigma of the same flower or of another flower is called pollination. Pollination is a prerequisite for fertilization. Seeds cannot form without pollination.<\/p>\n
Question 73.
\nName the two types of pollination found in plants.
\nAnswer:
\nThe two types of pollination in plants are<\/p>\n
\n- self-pollination<\/li>\n
- cross-pollination.<\/li>\n<\/ul>\n
Question 74.
\nDistinguish between self-pollination and cross-pollination.
\nAnswer:
\nThe transfer of pollen from the anther of a flower to the stigma of the same flower is called self-pollination. The transfer of pollen from the anther of a flower to the stigma of another flower of the same plant or a different plant of the same species is called cross-pollination.<\/p>\n
<\/p>\n
Question 75.
\nWhat is fertilization in plants? When and where does it occur?
\nAnswer:
\nThe fusion of male and female gametes resulting in the formation of a zygote in a flowering plant is known as fertilization. Fertilization occurs after pollination. Fertilization occurs in the ovaries.<\/p>\n
Question 76.
\nHow do pollens reach the ovaries of a flower? Explain.
\nAnswer:
\nPollen somehow gets deposited on the stigma of the carpel. For fertilization to occur, these pollens must reach the ovule through the style. The pollen grains on the stigma of a flower will develop a pollen tube that extends up to the ovule through the style. Pollens, which carry the male sex cells, will now move through the pollen tube.<\/p>\n
Once the pollen tube reaches an ovule, it delivers sperm cells with a burst, which goes to the embryo sac. The sperm cell fertilizes the egg cell to form an embryo, which will develop into a seed. The seed is a potential future plant.<\/p>\n
Question 77.
\nDraw a neat, labelled diagram showing the germination of pollen on stigma.
\nAnswer:
\n<\/p>\n
Question 78.
\nAfter fertilization in a flower, which part develops into fruit, seed coat and seed?
\nAnswer:
\nAfter fertilization in a flower, the ovary grows rapidly and ripens to form a fruit. The ovule becomes a seed. The covering of the ovule develops into seed coat.<\/p>\n
Question 79.
\nWhat changes occur in the flower after pollination and fertilization?
\nAnswer:
\nAfter pollination and fertilization get over, the following changes occur in the flower<\/p>\n
\n- The embryo develops into a seed, which later can grow into a new plant.<\/li>\n
- A nutritive tissue develops around the embryo, which stores nutrients.<\/li>\n
- The covering of the ovule forms the seed coat.<\/li>\n
- Ovary part of the carpel gets transformed into a fruit.<\/li>\n
- Sepals, petals and other parts of the flower will fall off.<\/li>\n<\/ol>\n
Question 80.
\nWhat are the advantages of seed formation for a plant?
\nAnswer:
\nSeed formation provides the following advantages to a plant<\/p>\n
\n- Seeds have reserve food sources which provide nourishment to the developing embryo.<\/li>\n
- They protect the embryo from harsh environmental conditions and enable the embryo to survive for long periods.<\/li>\n
- The seeds are easily dispersed by natural agents. The dispersal of seeds to far-off places prevents competition among the members of the same species, thus preventing their extinction.<\/li>\n
- Seeds can survive without water. If there is a drought, the plants can survive.<\/li>\n
- Seeds are produced in large numbers, which facilitates plants to multiply.<\/li>\n<\/ol>\n
Question 81.
\nHow is the process of pollination different from fertilisation?
\nAnswer:
\nTransfer of pollen grains from anther to stigma is called pollination. On the other hand, fusion of male and female gametes is called fertilization. Pollination is a physical process in which movement of pollen grains is achieved by certain physical factors. Fertilization is a biological process.<\/p>\n
Ovary is the site of fertilization and embryo is the product of fertilization. Pollination involves only the male gamete (pollen grain). Fertilisation involves both male and female gametes.<\/p>\n
Question 82.
\nWhat is germination of a seed? Explain.
\nAnswer:
\nThe development of a plant from a seed is called seed germination. The development of a seed into a plantlet after it has been planted in soil and remained dormant for a certain period of time is called germination. When seeds get into the soil, they remain inactive until conditions are suitable for germination. When they get favourable conditions, they germinate and a new young plant emerges.<\/p>\n
<\/p>\n
Question 83.
\nDescribe a simple activity to show the different parts of a seed.
\nAnswer:
\n
\nSoak a.few seeds of Bengal gram and keep them overnight. Drain the excess water. Cover the soaked seeds with a wet cloth and leave them for a day. Make sure that the seeds do not become dry. Cut open the seeds carefully and observe the different parts.<\/p>\n
We observe the brownish seed coat that encloses the two cotyledons. The cotyledons are laden with stored food material which help the seedling in the early stage of its development. We can also see a small embryo in between the two cotyledons.<\/p>\n
Question 84.
\nWhat type of reproduction and development happens in humans?
\nAnswer:
\nFluman beings reproduce by sexual method. The development is direct. This means a newly born baby resembles the adult in appearance, body parts and their functioning.<\/p>\n
Question 85.
\nWhat is fertilization? Where does it occur in humans?
\nAnswer:
\nThe process of formation of a single cell by the union of male sex cell (sperm) and female sex cell (ovum) is called fertilization. In humans, fertilization is internal. It occurs inside the female body.<\/p>\n
Question 86.
\nWhat is a zygote? Compare the number of chromosomes present in a sex cell with those present in the zygote.
\nAnswer:
\nA single cell formed by the union of male gamete and female gamete is called zygote. Zygote contains twice the number of chromosomes present in a sex cell that caused its formation.<\/p>\n
Question 87.
\nWhy are sex cells said to be haploid?
\nAnswer:
\nBoth the male sex cell (sperm) and the female sex cell (ovum) contain half the number of chromosomes present in other cells of the organism. For example, the cells in our body contain 46 chromosomes. However, the male and female sex cells of a human being will have only 23 chromosomes each. This is why sex cells are said to be haploid.<\/p>\n
Question 88.
\nA flowering plant has 24 chromosomes in its male gamete,<\/p>\n
\n- How many chromosomes are present in its female gamete?<\/li>\n
- What is the number of chromosomes in its zygote?<\/li>\n<\/ol>\n
Answer:<\/p>\n
\n- 24 chromosomes (both gametes should contain same number of chromosomes).<\/li>\n
- 48 chromosomes are present in its zygote. The union of male and female gametes forms zygote and hence the chromosomes add up.<\/li>\n<\/ol>\n
Question 89.
\nWhat is puberty?
\nAnswer:
\nThe period in life when a boy or girl becomes sexually mature and capable of sexual reproduction is called puberty. It is marked by several marked changes in the body. It is associated with the development of secondary sex characteristics and rapid growth. It is a process that usually happens between ages 10 and 14 in girls and ages 12 and 16 in boys.<\/p>\n
Question 90.
\nWhat are the changes seen in eirls at the time of puberty?
\nAnswer:
\nThe following changes are seen in girls at the time of puberty<\/p>\n
\n- The size of the breasts begins to increase.<\/li>\n
- Hairs grow in the arm pits and around the genitals.<\/li>\n
- The nipples at the tip of the breasts become relatively dark.<\/li>\n
- Menstruation cycle begins at around this time and continues periodically.<\/li>\n
- The voice becomes shriller and more feminine.<\/li>\n
- The pelvic region becomes broader.<\/li>\n
- The reproductive organs mature and become functional.<\/li>\n<\/ol>\n
Question 91.
\nWhat are the changes seen in boys at the time of puberty?
\nAnswer:
\nThe following changes are seen in boys at the time of puberty<\/p>\n
\n- Hairs appear in armpits, around the genitals, face (beard and moustach) and all over the body.<\/li>\n
- The voice breaks and becomes hoarse.<\/li>\n
- Gain height and weight. Hairs may appear on the chest.<\/li>\n
- The body becomes muscular and shoulders broaden.<\/li>\n
- Reproductive organs develop and become functional.<\/li>\n<\/ol>\n
<\/p>\n
Question 92.
\nWhat are some of the common changes observed in boys and girls at puberty?
\nAnswer:
\nThe following are some of the common changes in boys and girls during puberty:<\/p>\n
\n- Hairs appear in both boys and girls in armpits and genital area between the thighs.<\/li>\n
- The genital area becomes darker in both boys and girls.<\/li>\n
- Hairs on arms and legs appear and become darker.<\/li>\n
- The skin becomes oily and pimples may appear on the face in both boys and girls.<\/li>\n
- Both boys and girls become conscious of their own body as well as those of others.<\/li>\n<\/ol>\n
Question 93.
\nName the parts of the male reproductive system in humans.
\nAnswer:
\nThe male reproductive system in humans consists of<\/p>\n
\n- two testicles (testes)<\/li>\n
- the duct system that includes epididymis and vas deferens<\/li>\n
- the accessory glands which include seminal vesicles and prostate gland, and<\/li>\n
- penis.<\/li>\n<\/ul>\n
Question 94.
\nDraw a diagram of the male reproductive system in humans and label the parts.
\nAnswer:
\n<\/p>\n
Question 95.
\nWhat are testes? Where are they located in the human body?
\nAnswer:
\nOval shaped reproductive gland in the body of a human male is called testis. There are two testes in the human body. Testes are located within the loose pouch of skin called scrotum that hangs outside the body behind the penis.<\/p>\n
Question 96.
\nWhat is scrotum? What is their function?
\nAnswer:
\nA small muscular sac, which forms a part of the external male genitalia located behind and underneath the penis and houses the testicles is called scrotum. The scrotum holds and protects the testicles and keeps them at the right temperature.<\/p>\n
The production of sperms requires relatively lower temperature and therefore the temperature in the scrotum is lesser than the temperature of the rest of the body. Under cold conditions, scrotum pulls the testicles closer to the body and when the conditions are warmer, testicles hang away from the body.<\/p>\n
Question 97.
\nWhat are the functions performed by the testis in human beings?
\nAnswer:
\nTestis in human beings has twin functions. It produces male gametes namely the sperms. It also produces male sex hormone called testosterone, which is responsible for the development of secondary sexual characteristics in males.<\/p>\n
Question 98.
\nWhat is a sperm? Describe the structure of a sperm cell.
\nAnswer:
\nThe male reproductive cell is called sperm. A human sperm cell consists of an oval shaped head, a mid-piece and a long tail. The tail helps to make the sperm move easily in a fluid medium.<\/p>\n
Question 99.
\nWhat is the function of the tail in a sperm?
\nAnswer:
\nThe long tail of a sperm has a wavy motion with the help of which the sperm cell moves easily to the site of fertilization in the body of a female.<\/p>\n
Question 100.
\nWhat is sperm duct? What is its other name? What is its function?
\nAnswer:
\nThe duct that conveys sperms in a male from the testicle to the urethra is called sperm duct. It is also called vas deferens. It is a coiled duct that provides a pathway for the transport of sperms to the penis.<\/p>\n
<\/p>\n
Question 101.
\nWhat is penis? What is its function?
\nAnswer:
\nThe external muscular genital structure in males that carries the duct for the transfer of sperms to the female body is called penis. Biologically, penis has two main functions. It is an organ for urination, and passing on the sperms to the reproductive system of the female body for procreation.<\/p>\n
Question 102.
\nName any two reproductive accessory glands in the body of humans.
\nAnswer:
\nThe accessory glands associated with the reproductive system in humans include seminal vesicles and prostate gland.<\/p>\n
Question 103.
\nWhat is the role of the seminal vesicles and the prostate eland?
\nAnswer:
\nSeminal vesicles and prostate gland form an important part of the male reproductive system. The seminal vesicles and prostate gland add their secretions to sperms to make up the semen. The secretions of seminal vesicles and prostate gland provide nutrition to the sperms and also provide a suitable medium for their easy transport.<\/p>\n
Question 104.
\nHow are the sperms produced in testes delivered to the female body for fertilization?
\nAnswer:
\nSperms are produced in the testes and are stored there temporarily. They are delivered through the vas deferens, which unites with a tube coming from the urinary bladder. The urethra thus forms a common passage for both the sperms and urine. Along the path of the vas deferens, glands like the prostate and the seminal vesicles add their secretions to the sperms to form semen.<\/p>\n
The sperms are now in a fluid medium, which makes their transport easier. The substances in the fluid will also provide nutrition to the sperms. The semen containing sperms is delivered by the penis into the vaginal passage of the female during intercourse. The sperms further travel upwards and reach the oviduct where one of the sperms may fertilize the egg.<\/p>\n
Question 105.
\nMention the three major functions of the female reproductive system.
\nAnswer:
\nThe three major functions of the female reproductive system are<\/p>\n