CBSE Class 10 Science Important Questions Chapter 8 How Do Organisms Reproduce Part 2

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2 Marks Questions

1. Define reproduction. Why is it important?

Ans. It is a process by which organisms are able to produce new organisms of their own kind. It is important to maintain continuity of life.

2. What is callus?

Ans. In artificial vegetative propagation, an isolated plant part called explants is cultured in glass container under aseptic conditions with proper nutrient medium. The explants develop into undifferentiated mass of cells called callus.

3. What happens if the mature ovum is not fertilized in a female? Name the process

Ans. If mature egg is not fertilized it gets released into fallopian tubes. This process is known as menstruation.

4. Give two examples each of IUCD and STD.

Ans. IUCD – Copper–T, loops

STD – Syphilis, gonorrhoea

5. What do you understand by self-pollination & cross pollination? Give examples of each.

Ans. Self-pollination - It is the transfers of pollen grains form an anther to the stigma of the same plant. If it is in the same flower, it is called auto gamy and if it is between flowers of the same plant, then it is called geitonogamy.

Cross pollination – It is the transfer of pollen grains from anther to the stigma of different plants of the same species.

6. What is the difference between binary fission and multiple fission?


Binary fission and multiple fission

Binary Fission

Multiple Fission

It is type of asexual reproduction in which one parent organism divides into two new organisms. For ex- Amoeba

It is a type of asexual reproduction in which one parent organism for ex- Plasmodium

7. What are the basic features of asexual reproduction?

Ans. Basic feature for asexual reproduction are:

(1) Only one organism is involved.

(2) Cell divisions are either amitotic or mitotic.

(3) New organisms are genetically identical to parents.

(4) Formation of gametes and their fertilization does not occur.

8. What is a clone? Why offspring do’s formed by asexual reproduction exhibit remarkable similarity?

Ans. Cells derived from a common ancestor are known as clone. Offspring obtained from asexual reproduction has only one parent, their is no chances of variation in their chromosomes. Hence, they are exactly similar with their parents.

9. List two important functions of gonads.

Ans. Functions of gonads

a) It produces gametes in male and female

b) It produces sex hormones

10. What is the function of Cowper’s gland and prostate gland?

Ans. Cowper’s glands – It secretes a white, viscous and alkaline secretion which acts as lubricant.

Prostate gland – The secretion of this gland keeps the sperm active and mobile.

11. List various reproductive parts of flower

Ans. Reproductive organs of flower are –

a) Androecium (male reproductive part) – It has two parts filament and anther. Another has four pollen sacs which contain pollen grains. Pollen grains produce two male gametes.

b) Gynoecium (Female reproductive part) – It has three parts – ovary, style and stigma.

12. What is the difference between internal & external fertilization?


Internal & external fertilization

Internal fertilization

External fertilization.

Male gametes are discharged inside the body of female.

Both male & female gametes are discharged outside the body.

Fusion of gametes occurs inside the body of female parent.

Outside the body of female parent

For ex- Insects, reptiles, birds & human beings

For ex- fishes & amphibians.

13. Name the type of reproduction involved in the following –

(i) A slice of bread has greenish – yellow patches.

(ii) Potato in the store room starts sprouting

Ans. i) Spore formation

ii) Vegetative propagation

14. Give two reasons for the appearance of variations among the off springs formed by sexual reproduction.

Ans. An offspring produced by sexual reproduction has variations because –

a) It involves two parents, so the offspring has some characteristics of male and some of female.

b) Copying of DNA is not exactly same as parent.

15. Name the organism causes syphilis. Mention two symptoms.

Ans. Syphilis is caused by bacteria. Symptoms are –

a) Causes sores and lesions in the genital tract.

b) Burning sensation at urination.

16. How does human foetus derive nutrition?

Ans. A special disc like structure is formed between the embryo and the uterus wall called placenta. It is a connection between the mother and the foetus. This disc remains embedded in the uterine wall. It contains villi on the embryo’s side of the tissue. On the mother’s side are blood spaces, which surround the villi. This provides a large surface area for the transfer of nutrients mother to foetus.

17. Why are testes and ovaries considered as primary sex organs?

Ans. Testis and ovaries are called primary sex hormones because they produce gametes and sex hormones.

18. What is the difference between fission and budding?


fission and budding?



It is type of asexual reproduction in which one parent organism divides into two or many new organisms

It is type of reproduction in which out growth (bud) is formed on the parent organism and it separates to form new organism

Parental Identity lost

Parental identity maintained

19. Mention function of testis in humans?

Ans. Function of testes –

a) Spermatogenesis – Testes produce male gametes sperm.

b) Secretion of hormone – Testes secrete hormone testosterone – the male sex hormone which helps in regulation of spermatogenesis and also maintains structure and function of secondary sex characters like facial, axial and public hair, voice moustache, etc.

20. Why does menstruation occur?

Ans. When ovum does not get fertilized, due to non – availability of sperm in the female body, then longer needed and hence it breaks. So, the thick and soft inner lining of uterus along with the blood vessels and the dead ovum comes out of the vagina in the form of blood, called menstruation.

21. How will an organism be benefited if it reproduce through spores?

Ans. The spores are covered by thick walls that protect them until they come into contact with suitable moist surface and can begin to grow.

22. How is process of pollination different from fertilization?

Ans. Distinction between pollination and fertilisation:

Pollination and fertilisation



Pollination refers to the process of transfer of pollen grains from anther to stigma of flower.

Fertilisation refers to fusion of male and female gamete to form a zygote.

23. What is the role of the seminal vesicles and the prostate gland?

Ans. Secretions of seminal vesicles and prostate gland provide fluid medium to sperm to move and also provide nutrition to them.

24. What are the changes seen in girls at the time of puberty?

Ans. During puberty breast size begins to increase with darkening of the skin of the nipples at the tip of breasts. Also, girls begin to menstruate at around this time.

25. If a woman is using a copper-T, will it help in protecting her from sexually transmitted diseases?

Ans. Copper-T cannot protect the woman from acquiring sexually transmitted disease. It will protect her from only unwanted pregnancy.

26. What are the advantages of sexual reproduction over asexual reproduction?

Ans. Sexual reproduction leads to variation due to recombination of genetic material DNA. These variations are essential for survival of species. On the contrary, asexual reproduction does not bring about variations.

27. What are the functions performed by the testis in human beings?

Ans. In human beings, testes performs dual function:

(i) Production of sperms

(ii) Secretion of male hormone testosterone.

28. How are the modes of reproduction different in unicellular and multicellular organism?

Ans. In unicellular organisms, cell division, or fusion leads to the creation of new individuals.

In multicellular organisms with simple body organization budding, fragmentation may work but in complex multicellular organisms only sexual reproduction takes place.

29. How does reproduction help in providing stability to populations of species?

Ans. The consistency of DNA copying during reproduction is important for the maintenance of body design features that allow the organism to use the particular niche. Reproduction is, therefore, linked to the stability to populations of species.

30. A couple wants to space the birth of their second child. Suggest one preventive method which could be observed

(a) By the husband

(b) By the wife for the same.

Ans. (a) Use of condoms by the husband

(b) Use of oral pills or loop or Copper-T by the wife.

31. A girl attains her puberty at the age of 11 years and a boy at 13 years but, still they are asked to refrain from sex, why?

Ans. They are asked to refrain from sex because:

1. They are not physically, emotionally mature enough to be able to bear the responsibility of the child.

2. They may suffer from reproductive tract infections.

32. A pregnant woman visits a doctor to determine the sex of her child. The doctor refused to perform the test. Why is she being denied?

Ans. The doctor refused to perform the test in order to prevent female feticide which leads to an alarming decline in child sex ratio.

33. Blue prints of body design are stored in the DNA. Why?

Ans. The chromosomes present in the nucleus of a cell contain information for inheritance of features from parents to next generation in the form of DNA molecule. The DNA is the information source for making proteins. Thus, blueprints of the body design are stored in the DNA.

34. Protozoan reproduce by binary fission as well as by multiple fission. In your opinion which process is better and why? 2 Marks

Ans. Multiple fission is better than binary fission because:

1. More number of individuals is produced.

It helps to tide over unfavourable conditions.

35. What causes joining up of stock and scion in grafting technique of vegetative propagation in plants? Define the terms stock and scion. Name one positive trait each of the plant contributing scion and stock should have.

Ans. Stock is the root of the plant which is being grafted on and scion is the plant which is grafted on the stock. Any desirable trait which is required in the offspring is the positive trait. For Example, large no. of fruit production.

36. Why is it said that “sexual reproduction promotes diversity of characters in the off springs”?

Ans. It is because sexual reproduction results from the fission of two gametes coming from two different and sexually distinct individuals. This leads to variation, is necessary for evolution.

37. Name the causative organism of syphilis and gonorrhoea grafted on the other plant and it contributes the stem. The plant contributing scion should have large sized fruits and the plant contributing stock should have deep root system.

Ans. Treponema pallidum and Nisseria gonorrhoeae.

38. What happens if the fallopian tubes are partially blocked and the ovulated eggs are prevented from reaching the uterus?

Ans. Fertilization may take place but the zygote may develop in the tube Stead of uterus.

39. Why are variation possible in progeny of sexually reproductive individuals?

Ans. Variations are possible in progeny of sexually reproductive individuals because copy of DNA in newly formed cell is not identical to copy DNA of original cell.