1.  When is reproduction said to be sexual.
Ans: The mode of reproduction in which a male and a female gamete fuse to produce a zygote is called sexual reproduction.

2.  What is metamorphosis Give examples.
Ans: The drastic change which takes place during the development of an animal is called metamorphosis. Silkworm and frog undergo metamorphosis.

3.  Differentiate between internal fertilisation and external fertilisation.
Ans :

                Internal Fertilisation                External Fertilisation
(a) Fertilisation that takes place inside the female body.
(b) Takes place in humans, cows, hens and dogs.
(a) Fertilisation that takes place outside the female body.
(b) Takes place in frogs, fishes and starfish.

4.  Explain the importance of reproduction in organisms.
Ans: Reproduction is essential for the survival of organisms. It ensures the continuation of similar kinds of individuals, generation after generation.

5.  Differentiate between sexual and asexual reproduction.

    Sexual Reproduction      Asexual Reproduction
(a) Reproduction which takes place by the fusion of male and female gametes.
(b) Takes place in humans, cow.
(a) Reproduction in which only a single parent is involved.
(b) Takes place in hydra and amoeba.

6.  How many sperms are produced by the testis.
Ans: Millions of sperms are produced by the testis.

7.  What is the function of ovaries, in human beings, how many eggs are produced every month.
Ans: Ovaries produce female gametes called ova. In human beings, a single mature egg is released every month.

8.  If millions of sperms are transferred from the male to the female body, how many fuse with the egg.
Ans: Only one sperm fuses with the egg.

9.  Draw a diagram to show fertilisation in humans.

10.  What is a zygote?
Ans: A fertilized egg is called Zygote.

11.  How does the size of the egg varies in different animals.
Ans: The egg is very small in humans, much larger in hens and the largest in ostrich.

12.  The eggs of a frog are covered by a layer of jelly. Why.
Ans: The layer of jelly protects the eggs and holds them together.

13.  What is binary fission.
Ans: Binary fission is a mode of reproduction in unicellular organisms by which a single individual divides into two parts and each part live as two independent individuals.

14.  Name any two animals that undergo metamorphosis.
Ans: Silkworm and frog

15.  What is fertilisation. Differentiate between external and internal fertilisation.
Ans: Fusion of male sperms and female ova is called fertilisation.

External fertilisation Internal fertilisation
i) When male gamete fuses with the female gamete outside the body of female,
e.g. In fishes and frogs.
i) When male gamete fuses with the female gamete inside the body of female,
e.g. In dogs and human beings.

16.  What do you mean by viviparous animals.
Ans: Viviparous animals are the animals which give birth to their young ones.

17.  Draw a labelled diagram to show the male reproductive system in human beings.

18.  Draw a labelled diagram to show the female reproductive system in human beings.

19.  Explain how external fertilisation takes place in frogs.
Ans: During rainy season, frogs and toads move to ponds. When the male and female come together in water, the female lays hundreds of eggs. A layer of jelly holds the eggs together. The male deposits the sperms over them and fertilisation takes place.

20.  Name an organism that reproduces by budding.
Ans: Hydra.

21.  Name any two methods of asexual reproduction.
Ans: Budding and Binary fission.