NCERT CLASS 10 SCIENCE CHAPTER 7 HOW DO ORGANISM REPRODUCE
NCERT CLASS 10 SCIENCE
CHAPTER 7 – HOW DO ORGANISMS REPRODUCE?
IN-TEXT QUESTIONS AND ANSWERS
1. What is the importance of DNA copying in reproduction?
DNA copying is important because it transfers hereditary information from parents to offspring. It ensures continuity of body design while also introducing small variations. These variations help organisms adapt to changing environmental conditions.
2. Why is variation beneficial to a species but not necessarily beneficial to an individual?
Variations increase the chances that some individuals in a species will survive environmental changes. However, a particular variation may not always provide an advantage to the individual organism.
3. How does binary fission differ from multiple fission?
Binary fission: One parent cell divides into two daughter cells. Example: Amoeba.
Multiple fission: The nucleus divides repeatedly, followed by division of the cytoplasm, producing many daughter cells at the same time. Example: Plasmodium.
4. How will an organism benefit if it reproduces through spores?
Spore formation provides several advantages:
Spores are produced in large numbers.
They have thick protective walls.
They can survive unfavourable conditions.
They can grow into new organisms when conditions become favourable.
5. Can you think of reasons why more complex organisms cannot reproduce through regeneration?
Complex organisms have specialised cells, tissues and organs. Their body parts are highly organised and cannot usually develop into a complete organism. Regeneration in complex organisms generally helps repair or replace damaged body parts rather than produce new individuals.
6. Why is vegetative propagation practised for growing some types of plants?
Vegetative propagation is useful because:
It produces new plants quickly.
The new plants are genetically similar to the parent plant.
Plants that do not produce viable seeds can be grown through this method.
Some plants flower and produce fruits earlier than seed-grown plants.
7. Why is DNA copying an essential part of reproduction?
DNA contains the genetic information required for the development and functioning of an organism. Copying DNA transfers this information to the next generation and allows hereditary characteristics to continue.
8. How is the process of pollination different from fertilisation?
Pollination: It is the transfer of pollen grains from the anther to the stigma of a flower.
Fertilisation: It is the fusion of the male and female gametes to form a zygote.
9. What is the role of the seminal vesicles and prostate gland?
The seminal vesicles and prostate gland add secretions to the sperms. These secretions provide nourishment, help sperm movement and form part of the semen.
10. What are the changes seen in girls at the time of puberty?
The major changes include:
Development of breasts.
Growth of hair in the armpits and pubic region.
Widening of hips.
Beginning of menstruation.
Maturation of reproductive organs.
Changes in body shape and other physical features.
11. How does the embryo get nourishment inside the mother's body?
The embryo receives nutrients and oxygen from the mother's blood through a special tissue called the placenta. The placenta also helps remove carbon dioxide and waste materials produced by the embryo.
12. If a woman is using a copper-T, will it help protect her from sexually transmitted infections?
No. Copper-T is an intrauterine contraceptive device used to prevent pregnancy. It does not protect against sexually transmitted infections.
EXERCISE QUESTIONS AND ANSWERS
1. What is the importance of DNA copying in reproduction?
DNA copying transfers hereditary information from parents to offspring. It maintains the basic characteristics of a species and introduces small variations that contribute to evolution and adaptation.
2. Why is variation beneficial to a species but not necessarily beneficial to an individual?
Variation increases the possibility that some members of a species will survive when environmental conditions change. However, a particular variation may be harmful, neutral or beneficial to an individual.
3. How does binary fission differ from multiple fission?
Binary fission:
One parent cell divides into two daughter cells.
It generally involves one nuclear division followed by cytoplasmic division.
Example: Amoeba.
Multiple fission:
The nucleus divides repeatedly.
The cytoplasm divides around the daughter nuclei.
Many daughter cells are produced at once.
Example: Plasmodium.
4. How will an organism benefit if it reproduces through spores?
Spore formation allows organisms to produce many offspring. Spores have protective walls that help them survive unfavourable conditions. They germinate when suitable conditions become available.
5. Why can more complex organisms not reproduce through regeneration?
Complex organisms have specialised tissues and organs that perform different functions. Their cells are organised into complex body systems. Therefore, a small body part usually cannot develop into a complete organism. Regeneration in such organisms mainly helps replace damaged or lost parts.
6. Why is vegetative propagation practised for growing some types of plants?
Vegetative propagation:
Produces plants quickly.
Helps grow plants that do not produce viable seeds.
Preserves desirable characteristics of the parent plant.
Allows plants to mature and flower earlier in some cases.
Examples include potato, sugarcane, rose and Bryophyllum.
7. Why is DNA copying essential for reproduction?
DNA copying is essential because DNA carries hereditary information. It ensures that offspring receive genetic information from their parents. Small differences during copying also introduce variations.
8. How is the process of pollination different from fertilisation?
Pollination:
Transfer of pollen grains from anther to stigma.
It takes place before fertilisation.
It may occur through wind, water, insects and other agents.
Fertilisation:
Fusion of male and female gametes.
It results in the formation of a zygote.
It takes place inside the female reproductive structure of the flower in flowering plants.
9. What is the role of the seminal vesicles and prostate gland?
The seminal vesicles and prostate gland produce secretions that mix with sperms. These secretions provide nutrients and help sperm movement. The mixture of sperms and glandular secretions is called semen.
10. What are the changes seen in girls at the time of puberty?
The changes include:
Development of breasts.
Growth of hair in the armpits and pubic region.
Widening of the hips.
Beginning of menstruation.
Maturation of reproductive organs.
Increased activity of sweat and oil glands.
11. How does the embryo get nourishment inside the mother's body?
The embryo receives nutrients and oxygen through the placenta. The placenta is connected to the embryo by the umbilical cord. It also allows carbon dioxide and waste materials to pass from the embryo into the mother's blood for removal.
12. If a woman is using a copper-T, will it help protect her from sexually transmitted infections?
No. Copper-T is a contraceptive device placed inside the uterus to prevent pregnancy. It does not provide protection against sexually transmitted infections.
13. What are the advantages of sexual reproduction over asexual reproduction?
Sexual reproduction produces genetic variations because genetic material from two parents combines. These variations increase the chances of adaptation and survival when environmental conditions change. Asexual reproduction generally produces offspring that are genetically very similar to the parent.
FEW IMPORTANT ADDITIONAL QUESTIONS AND ANSWERS
1. What is reproduction?
Reproduction is the biological process by which living organisms produce new individuals of their own kind. It ensures the continuity of a species from one generation to the next.
2. What are the two main types of reproduction?
The two main types are:
Asexual reproduction: A single parent produces offspring without the formation and fusion of gametes.
Sexual reproduction: Male and female gametes fuse to form a zygote, which develops into a new organism.
3. What is asexual reproduction? Give examples.
Asexual reproduction is a process in which a single parent produces offspring without the fusion of male and female gametes.
Examples:
Binary fission in Amoeba.
Budding in Hydra.
Spore formation in Rhizopus.
Fragmentation in Spirogyra.
Vegetative propagation in potato.
4. What is sexual reproduction?
Sexual reproduction is a process in which male and female gametes fuse to form a zygote. The zygote develops into a new individual.
5. What is the difference between sexual and asexual reproduction?
Asexual reproduction:
Usually involves one parent.
No fusion of gametes takes place.
Offspring are generally genetically similar to the parent.
It is usually faster.
Example: Binary fission in Amoeba.
Sexual reproduction:
Generally involves two parents.
Fusion of male and female gametes takes place.
Offspring show genetic variations.
It involves specialised reproductive cells.
Example: Reproduction in humans.
6. Explain binary fission with an example.
Binary fission is a type of asexual reproduction in which one parent cell divides into two daughter cells.
In Amoeba, the nucleus first divides into two nuclei. Then the cytoplasm divides, producing two daughter Amoebae.
7. Explain budding with an example.
Budding is a type of asexual reproduction in which a small outgrowth develops on the parent body. The bud grows and eventually separates to form a new individual.
Example: Hydra and yeast.
8. What is fragmentation?
Fragmentation is a type of asexual reproduction in which the body of an organism breaks into smaller fragments. Each fragment can grow into a complete organism under suitable conditions.
Example: Spirogyra.
9. What is regeneration?
Regeneration is the ability of an organism to develop new tissues or body parts from certain body fragments. In some simple organisms, a complete new individual can develop from a body fragment.
Example: Planaria.
10. What is spore formation?
Spore formation is a type of asexual reproduction in which an organism produces small reproductive structures called spores. Under favourable conditions, spores germinate and develop into new organisms.
Example: Rhizopus.
11. What is vegetative propagation?
Vegetative propagation is a type of asexual reproduction in plants in which new plants develop from roots, stems or leaves instead of seeds.
Examples:
Potato – stem tuber.
Ginger – underground stem.
Bryophyllum – leaves.
Sugarcane – stem.
Rose – stem cutting.
12. What are the advantages of vegetative propagation?
New plants can be produced quickly.
Desirable characteristics are preserved.
Plants that do not produce viable seeds can be grown.
Many plants can be produced from a single parent plant.
13. What are the main parts of a flower?
The main parts of a flower are:
Sepals: Protect the flower bud.
Petals: Often attract insects and other pollinators.
Stamens: Male reproductive parts.
Pistil or carpel: Female reproductive part.
14. What is the male reproductive part of a flower?
The stamen is the male reproductive part of a flower. It consists of:
Anther: Produces pollen grains.
Filament: Supports the anther.
Pollen grains contain the male reproductive cells.
15. What is the female reproductive part of a flower?
The pistil or carpel is the female reproductive part of a flower. It consists of:
Stigma: Receives pollen grains.
Style: Connects stigma to ovary.
Ovary: Contains ovules.
16. What is pollination? Name its types.
Pollination is the transfer of pollen grains from the anther to the stigma of a flower.
Types:
Self-pollination: Transfer of pollen to the stigma of the same flower or another flower on the same plant.
Cross-pollination: Transfer of pollen from a flower of one plant to a flower of another plant of the same species.
17. What is fertilisation in plants?
Fertilisation is the fusion of the male gamete with the female gamete to form a zygote. In flowering plants, the male gamete reaches the ovule through the pollen tube.
18. What happens to the ovary and ovule after fertilisation?
After fertilisation:
The ovary develops into a fruit.
The ovary wall forms the fruit wall.
The ovule develops into a seed.
The zygote develops into an embryo.
19. Name the main parts of the human male reproductive system.
The main parts are:
Testes
Scrotum
Sperm ducts or vas deferens
Urethra
Penis
Accessory glands, including seminal vesicles and prostate gland.
20. What are the functions of testes?
Testes perform two important functions:
Produce male gametes called sperms.
Produce the male sex hormone testosterone.
21. Why are testes located outside the abdominal cavity?
Testes are located in the scrotum outside the abdominal cavity because sperm production requires a temperature slightly lower than normal body temperature.
22. What is the function of the vas deferens?
The vas deferens is a tube that carries sperms from the testes towards the urethra. It helps transport sperms during ejaculation.
23. Name the main parts of the human female reproductive system.
The main parts are:
Ovaries
Fallopian tubes or oviducts
Uterus
Cervix
Vagina
24. What are the functions of ovaries?
Ovaries:
Produce female gametes called ova or eggs.
Secrete female sex hormones, mainly oestrogen and progesterone.
25. What is the function of the uterus?
The uterus is the organ where the fertilised egg implants and the embryo develops. It provides protection and support to the developing embryo.
26. What is fertilisation in humans?
Fertilisation in humans is the fusion of a male sperm with a female egg. It generally takes place in the fallopian tube and results in the formation of a zygote.
27. What is implantation?
Implantation is the process in which the developing embryo attaches to the thick lining of the uterus.
28. What is the placenta? Write its functions.
The placenta is a special tissue that connects the developing embryo with the mother's body.
Functions:
Supplies oxygen and nutrients to the embryo.
Removes carbon dioxide and waste materials from the embryo.
Helps in the exchange of substances between maternal and foetal blood.
29. What is menstruation?
Menstruation is the periodic shedding of the thickened uterine lining when fertilisation does not occur. The lining, along with blood and tissue, passes out through the vagina.
30. What is puberty?
Puberty is the stage of life when the reproductive organs mature and the body becomes capable of reproduction. It is accompanied by physical and hormonal changes.
31. What are contraceptive methods?
Contraceptive methods are methods used to prevent unwanted pregnancy.
Examples:
Barrier methods such as condoms.
Hormonal methods such as contraceptive pills.
Intrauterine devices such as Copper-T.
Surgical methods such as vasectomy and tubectomy.
32. How do condoms help in preventing pregnancy and infections?
Condoms act as physical barriers that prevent sperms from entering the female reproductive tract. When used correctly, condoms also reduce the risk of many sexually transmitted infections.
33. What is the difference between vasectomy and tubectomy?
Vasectomy:
A male sterilisation method.
The vas deferens is cut or blocked.
Prevents sperms from entering the semen.
Tubectomy:
A female sterilisation method.
The fallopian tubes are cut or blocked.
Prevents the meeting of sperm and egg.
34. What are sexually transmitted infections (STIs)?
Sexually transmitted infections are infections that can spread mainly through sexual contact. Examples include gonorrhoea, syphilis and HIV infection.
35. Why is reproductive health important?
Reproductive health helps individuals understand their reproductive systems, maintain hygiene, prevent infections and make informed decisions about reproduction.
IMPORTANT DIFFERENCES
1. Difference between pollination and fertilisation
Pollination:
Transfer of pollen grains from anther to stigma.
Takes place before fertilisation.
Does not involve fusion of gametes.
Fertilisation:
Fusion of male and female gametes.
Takes place after pollination in flowering plants.
Results in the formation of a zygote.
2. Difference between binary fission and budding
Binary fission:
Parent organism divides into two daughter organisms.
Example: Amoeba.
Budding:
A small bud develops on the parent and grows into a new individual.
Example: Hydra.
3. Difference between sperm and ovum
Sperm:
Male reproductive cell.
Produced in the testes.
Usually small and motile.
Ovum:
Female reproductive cell.
Produced in the ovaries.
Larger and non-motile.
IMPORTANT TERMS TO REMEMBER
Reproduction – Production of new individuals.
DNA – Hereditary material present in cells.
Variation – Differences among individuals of the same species.
Binary fission – Division of one cell into two daughter cells.
Budding – Formation of a new individual from a small outgrowth.
Fragmentation – Reproduction through body fragments.
Regeneration – Formation of new tissues or body parts.
Spore formation – Reproduction through spores.
Vegetative propagation – Formation of new plants from vegetative parts.
Pollination – Transfer of pollen grains to the stigma.
Fertilisation – Fusion of male and female gametes.
Zygote – Cell formed after fertilisation.
Placenta – Tissue connecting the developing embryo with the mother.
Menstruation – Periodic shedding of the uterine lining.
Contraception – Prevention of pregnancy.
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