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Class 10 Science Chapter 8 How Do Organisms Reproduce?
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How Do Organisms Reproduce?
Chapter – 8
Textual Questions and Answers:
Page – 128
Q.1. What is the importance of DNA copying in reproduction?
Ans: The copying of DNA during reproduction is important because: The replication of DNA ensures that each daughter cell formed at the end of cell division, receives equal amount of DNA. If DNA won’t be copied then the daughter cells won’t receive all necessary genes.
Q.2. Why is variation beneficial to the species but not necessarily for the individual?
Ans: Variation is beneficial to the species but not necessarily for the individual because it lets a species adapt to the changing environment. Variations at individual level will not help in evolving, but would result in ageing, so variation from any source in an individual can be harmful. At species level, these variations make differences in generation which leads to evolution.
Page – 133
Q.1. How does binary fission differ from multiple fission?
Ans: In binary fission, the parent cell is divided into two daughter cells. In multiple fissions, the parent cell is divided into many daughter cells.
Q.2. How will an organism be benefited if it reproduces trough spores?
Ans: The reproduction by spores takes place in plants. Spores are covered by hard protective coat which enables them to survive under unfavourable condition like lack of food, lack of water and extreme temperatures. But when the conditions become favourable then the spores can grow to produce new plants. Thus, the reproduction by spores benefits the plants because by surviving under adverse conditions, the spores make these plants live forever.
Q.3. Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?
Ans: The tissues in complex organisms can not regenerate a new individual as they highly differentiated to perform specialised functions. For example, human skin cannot regenerate into a new individual as it is a highly differentiated tissue performing a designated function.
Q.4. Why is vegetative propagation practised for growing some types of plants?
Ans: Vegetative propagation is practised for growing some types of plants because:
(i) Characters of the plants can be preserved through successive generation.
(ii) Seedless plants can be grown through vegetative reproduction
(iii) Through cutting and grafting methods, flowers and fruits can be grown in a shorter time.
(iv) It is a cheaper, easier and more rapid method of plant propagation.
Q.5. Why is DNA copying an essential part of the process of reproduction?
Ans: Importance of DNA copying in a sexual reproduction is that the characteristics of the parent organisms are transmitted to its offsprings and at the same time some occasional variations are also produced in the offsprings.
Page – 140
Q.1. How is the process of pollination different from fertilisation?
Ans: Transfer of pollen grains from the anther to stigma is called pollination. On the other hand, the fusion of male and female gametes is called fertilisation. Pollination is a physical process in which movement of pollen grains are attained by certain physical factors. Fertilisation is a biochemical process. An ovary is the site of fertilisation and embryo is the product of fertilisation.
Q.2. What is the role of seminal vesicles and prostrate gland?
Ans: In human males, the seminal vesicle forms an accessory gland whose fluid secretion results in activation of the sperms.
Role of seminal vesicle:
- Produces the necessary fluids that eventually convert into semen.
- Supplies protection and required nutrition to the sperm.
The prostate gland is a part of the reproductive system in human males that envelopes the urethra. It passes an alkaline secretion to the semen when it flows through the urethra.
Role of the prostate gland:
- Stores the fluid that transports and nourishes the seminal fluid.
- Make sure that the sperm is firmly pressed into the prostatic urethra.
Q.3. What are the changes seen in girls at the time of puberty?
- Puberty refers to the physical transformation of a child’s body into an adult one capable of sexual reproduction.
- Girls often begin puberty at the age of eleven.
Changes that are seen in girls at the time of puberty:
- Girls’ breasts begin to develop during puberty.
- The ovaries grow in girls, and eggs begin to develop.
- Ovaries also begin to release mature eggs (Menstruation starts).
- As a result of increased sweat and sebaceous gland activity, girls develop acne and pimples.
- Hair grows under the arms, above the thighs, and in the pubic region.
Q.4. How dose the embryo get nourishment inside the mother’s body?
Ans: The embryo gets nourishment inside the mother body through a special tissue called placenta. The embryo grows inside the mother’s womb and gets nourishment from mother’s blood through the tissue called placenta. The placenta is a temporary organ that develops in the uterus during pregnancy. It attaches the fetus to the uterine wall. It also provides nutrients to the fetus and also allows the fetus to transfer waste product’s to the mother’s blood.
Q.5. If a women is using a copper – T, will it help in protecting her from sexually transmitted diseases?
Ans: No, the use of copper – T for contraception will not protect a women from sexually transmitted diseases.
Q.1. COM Asexual reproduction takes place through budding in:
Ans: (b) Yeast.
Q.2. Which of the following is not a part of the female reproductive system in human beings?
(c) Vas deferens.
(d) Fallopian tube.
Ans: (c) Vas deferens.
Q.3. The anther contains
(d) Pollen grains.
Ans: (d) Pollen grains.
Q.4. What are the advantages of sexual reproduction over sexual reproduction?
Ans: Advantages of sexual reproduction over sexual reproduction:
- More variations are found in sexual reproduction.
- Survival of a species in a population is easy.
- Offspring has characteristics of both parents.
- It can lead to the formation of new species.
- The chances of evolution increase.
Q.5. Why are the functions performed by testes in human beings?
Ans: Testes perform 2 functions in human beings, basically males (testes are a part of male reproductive system; located outside the abdominal cavity in scrotum)-
(i) The produce male gametes/ sex cells known as sperms.
(ii) Also, they produce male sex hormone testosterone which is responsible for appearance of secondary sexual characters in boys, for example- beard, moustache, deep voice, etc.
Q.6. Why does menstruation occur?
Ans: As a woman, your period is your body’s way of releasing tissue that it no longer needs. Every month, your body prepares for pregnancy.
The lining of your uterus gets thicker as preparation for nurturing a fertilized egg. An egg is released and is ready to be fertilized and settle in the lining of your uterus.
If the egg is not fertilized, your body no longer needs the thicker lining of the uterus, so it starts to break down and is eventually expelled, along with some blood, from your vagina. This is your period, and once it’s over, the process starts all over again.
Q.7. Draw a labelled diagram of the longitudinal section of a flower.
Q.8. What are the different methods of contraception?
Ans: The various method of contraception are: Barrier methods, chemical methods, use of Loop or copper – T and surgical method.
In the barrier methods of preventing pregnancy, the physical devices such as condoms and diaphragms are used.
In the chemical methods of preventing pregnancy, the femalls use oral pills.
The loop or copper – T are also very effective in preventing pregnancy. A loop or copper – T is placed inside the uterus by a doctor or a trained nurse.
Surgical methods of birth control are available for males as well as females. In males, a small portion of the sperm duct is removed by surgical operation and both the cut ends are ligated property. In females, a small portion of the oviducts is removed by surgical operation and the cut ends are ligated.
Q.9. How are the modes of reproduction different in unicellular and multicellular organisms?
Ans: The different modes of reproduction in unicellular organisms are fission, budding, etc. Here, the cell divides into two daughter cells and this process of cell division continues. Whereas, in multicellular organisms there is a different organ system for reproduction. The different modes of reproduction in multicellular organisms are vegetative propagation, spore formation, etc. In more complex organisms like humans and animals, the reproduction is through sexual reproduction.
Q.10. How does reproduction help in providing stability to populations of species?
Ans: Reproduction is the process of producing new individuals of the same species by existing organisms of a species, so, it helps in providing stability to population of species by giving birth to new individuals as the rate of birth must be at par with the rate of death to provide stability to population of a species.
Q.11. What could be the reasons for adopting contraceptive methods?
Ans: Contraceptive methods are mainly adopted because of the following reasons:
1. To prevent unwanted pregnancies.
2. To control population rise or birth rate.
3. To prevent the transfer of sexually transmitted diseases.
Multiple Choice Questions:
Q.1. The method of a sexual reproduction in plants in which intre callus is produced is:
(b) Vegetative propagation.
Ans: (a) Micropropagation.
Q.2. The anther contains:
(d) Pollen grains.
Ans: (d) Pollen grains.
Q.3. Which of the following is not a part of the female reproductive system in human beings?
(c) Vas deferens.
Ans: (c) Vas deferens.
Q.4. One of the following is not a part of human male reproductive system. This is:
(c) Seminal vesicle.
(d) Prostrate gland.
Ans: (b) Oviduct.
Q.5. Which of the following is not a sexually transmitted disease?
Ans: (b) Hepatitis.
Q.6. Which of the following method of contraception protects a person from acquiring a sexually transmitted disease?
(a) Oral pills.
(c) Copper -T.
Ans: (b) Condom.
Q.7. In which one of following birth control methods a small portion of oviducts of a woman is removed by surgical operation and the cut ends are ligated?
(a) Copper – T.
Ans: (b) Tubectomy.
Q.8. One of the following is a surgical method which prevents the sperms from reaching the ovum and pregnancy does not occur. This method is:
Ans: (b) Vasectomy.
Q.9. Fertilisation results immediately in the formation of:
(a) A zygote.
(b) An embryo.
(c) A placenta.
(d) A foetus.
Ans: (a) A zygote.
Q.10. The sexually transmitted discase which is caused by bacteria is:
Ans: (c) Gonorrhoea.
Q.11. AIDS is a deadly disease which is caused by :
(a) A protozoa.
(b) A fungus.
(c) A bacterium.
(d) A virus.
Ans: (d) A virus.
Q.12. In a flower, the parts that produce male and female gametes are respectively:
(a) Sepal and anther.
(b) Filament and stigma.
(c) Auther and overy.
(d) Stamen and style.
Ans: (c) Auther and overy.
Q.13. The characteristics transmitted from parents to offspring are present in:
(c) Golgi bodies.
Ans: (d) Genes.
Q.14. The two organisms which can regenerate fully from their cut body parts are:
(a) Paramecium and Hydra.
(b) Hydra and Amoeba.
(c) Planaria and Leishmania.
(d) Hydra and Planaria.
Ans: (d) Hydra and Planaria.
Q.15. The two types of organisms which produce colonies by the process of badding are:
(a) Hydra and Corals
(b) Yeast and Sponges.
(c) Corals and Sponges.
(d) Hydra and Yeast.
Ans: (c) Corals and Sponges.
Q.16. Spine formation is the most common asexual method of reproduction in:
Ans: (c) Furgi.
Q.17. An alga which reproduces by the asexual reproduction method called fragmentation is:
Q.18. Binary fission describes the type of reproduction where the organism divides to form:
(a) Many spores.
(b) Two daughters.
(c) Many buds.
(d) Two hyphae.
Ans: (b) Two daughters.
Q.19. The cut part of a plant step which is used in grafting is called:
Ans. (c) Scion.
Q.20. The cut part of plant stem which is used in the process of grafting is known is:
Ans: (a) Stock.
Q.21. Multiple fission occurs in one of the following . This is
(a) Bread mould.
(b) Kala – azar parasite.
(c) Flat worm.
(d) Malaria parasite.
Ans: (d) Malaria parasite.
Q.22. An organism having a whip – like structure at one end which reproduces by the process of binary fission is
Ans: (c) Leishmania.
Q.23. A tiny animal having tentacles which reproduces by growing buds on the sides of its body is:
Ans: (d) Hydra.
Q.24. An organism which can reproduce by two asexual reproduction methods one similar to the reproduction in Yeast and the other similar to the reproduction in Planaria is:
(d) Sea ane mone.
Ans: (c) Hydra.
Q.25. Stock and scion are induced in the artificial propagation method known as:
(a) Tissue culture.
Ans: (c) Grafting.
Q.26. In a sexual reproduction , two off springs having the same genetic material and the same body features are called:
Ans: (c) Alones.
Q.27. One of the following does not reproduce by spore formation method. This is
(a) Rhizopus fungus.
(b) Penicillium fungus.
(c) Yeast fungus.
(d) Mucor fungus.
Ans: (c) Yeast fungus.
Q.28. One of the following reproduces by forming spores. This in:
Ans: (a) Fern.
Q.29. Asexual reproduction through budding takes place in:
(i) Amoeba and yeast.
(ii) Yeast and Hydra.
(iii) Hydra and plasmodium.
(iv) Corals and sponges.
(a) (i) and (ii)
(b) only (ii)
(c) (i) and (iii)
(d) (ii) and (iv)
Ans: (d) (ii) and (iv)
Q.30. A feature of reproduction that is common to Amoeba, yeast and Bacterium is that:
(a) They are all multicellular.
(b) They are all unicellular.
(c) They reproduce only sexually.
(d) They reproduce asexually.
Ans: (d) They reproduce asexually.
Q.31. One of the following organisms does not reproduce by fission. This is:
Ans: (c) Planaria.
Q.32. An organism which may be considered to be a kind of plant and reproduces by budding is:
(b) Bread mould
Ans: (d) Yeast.
Q.33. An animal which reproduces by the process of budding is –
Ans: (c) Hydra.
Q.34. In spirogyra, a sexual reproduction takes place by:
(a) Division of cell into two cells
(b) Breaking up of filaments into smaller bits.
(c) Division of a cell into many cells.
(d) Formation of a large number of buds .
Ans: (b) Formation of a large number of buds.
Q.35. One of the following organisms does not reproduce by binary fission. This is
Ans: (b) Plasmodium.
Q.36. The micro – organism which reproduces by multiple fission is the one which causes the disease known as:
(a) Kala – azar.
Ans: (c) Malaria.
Q.37. The protozoa having a flagellum at its one end is
Ans: (d) Leishmania.
Q.38. In the list of organisms given below those which both reproduce by the asexual method are
(a) (ii) and (iv)
(b) (i) (iii) and (iv)
(c) (i) and (iv)
(d) (ii) (iii) and (iv)
Ans: (b) (i) (iii) and (iv)
Q.39. One of the following organism does not reproduced by bedding this is:
Ans: (d) Planaria.
Q.40. The disease Kala – azar is caused by a micro – organism knows as
Ans: (c) Leishmania.
Q.41. Reproduction is essential for living organisms in order to –
(a) Keep the individual organ alive.
(b) Fulfil their energy requirements.
(c) Maintain growth.
(d) Continue the species forever.
Ans: (d) Continue the species forever.
Q.42. The unicellular organism which reproduces by budding is –
Ans: (d) Yeast.
Q.43. A multicellular organism which reproduces by bedding is–
Ans: (d) Hydra.
Q.44. The offsprings formed by asexual reproduction method have greater similarity among similarity among themselves because–
(i) A sexual reproduction involves only one parent.
(ii) A sexual reproduction involves two parents.
(iii) A sexual reproduction involves gametes.
(iv) A sexual reproduction doesnot involves gameteo.
(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii) and (iv)
(d) (i) and (iv)
Ans: (d) (i) and (iv)
Q.45. A simple multicellular animal having tenlacles which lives in fresh water usually reproduces by the asexual process of:
(a) Binary fission.
(b) Spore formation.
Ans: (C) Bedding.
Q.46. The ability of a cell to divide into several cells during reproduction in plasmodium is called:
(c) Binary fission.
(d) Multiple fission.
Ans: (d) Multiple fission.
Q.47. Rhizopus fungus , the fine thread like structures spread on the whole surface of slice of bread are called:
Ans: (d) Hyphae.
Q.48. In human males, the testes lie in the scrotum outside the body because it helps in the:
(a) Process of mating.
(b) Formation of sperms.
(c) Easy transfer of sperms.
(d) All the above.
Ans: (b) Formation of sperms.
Q.49. In human females, an event that indicates the onset of reproductive phase is:
(a) Growth of body.
(b) Change in hair pattern.
(c) Change in voice.
Ans: (c) Change in voice.
Q.50. One of the following occurs in the reproductive system of flowering plants as well as that of human. This is –
Ans: (c) Overy.
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