Reproduction in Animals Class 8 Worksheet Science Chapter 6

Q.1. Name two animals which reproduce asexually.

Hydra, Amoeba

Q.2. Who cloned Dolly the sheep?

Dolly was cloned by Ian Wilmut and his colleagues at the Roslin Institute in Edinburgh, Scotland.

Q.3. Why do fish and frogs lay eggs in hundreds?

Though these animals lay hundreds of eggs and release millions of sperms, all the eggs do not get fertilized and develop into new individuals. This is because the eggs and sperms get exposed to water movement, wind and rainfall. Also, there are other animals in the pond which may feed on eggs. Thus, production of large number of eggs and sperms is necessary to ensure fertilization of at least a few of them.

Q.4. What is ‘in vitro fertilization’ technique of reproduction?

In some women oviducts are blocked. These women are unable to bear babies because sperms cannot reach the egg for fertilization. In such cases, doctors collect freshly released egg and sperms and keep them together for a few hours for IVF or in vitro fertilization (fertilization outside the body). In case fertilization occurs, the zygote is allowed to develop for about a week and then it is placed in the mother’s uterus. Complete development takes place in the uterus and the baby is born like any other baby. Babies born through this technique are called test-tube babies.

Q.5. Which type of reproduction does not involve gametes?

Asexual reproduction

Q.6. What are the reproductive organs in humans which produce the gametes?

The ovary produces female gametes called ova and the testes produce male gametes called sperms.

Q.7. Define asexual reproduction. Describe two methods of asexual reproduction in animals.

The type of reproduction in which only a single parent is involved is called asexual reproduction. The two methods of asexual reproduction in animals are:

Budding: In this type of asexual reproduction, a small part of the body of parent organism grows as a ‘bud’ which then detaches and becomes a new organism. Example- hydra

Binary fission: In this type of asexual reproduction, the parent organism splits (or divides) to form two new organisms. Example - Amoeba reproduces by binary fission by dividing itself into two parts.

Q.8. How does fertilization take place in frog?

During spring or rainy season, frogs and toads move to ponds and slow flowing streams. When the male and female come together in water, the female lays hundreds of eggs. Frog’s egg is not covered by a shell and it is comparatively very delicate. A layer of jelly holds the eggs together and provides protection to the eggs. As the eggs are laid, the male deposits sperms over them. Each sperm swims randomly in water with the help of its long tail. The sperms come in contact with the eggs. This results in fertilization.

Q.9. Name the reproductive process which involves two parents.

Sexual reproduction

Q.10. What are the male gametes in humans called?

The male gametes in humans are called sperms.

Q.11. What is an embryo?

The zygote divides repeatedly to give rise to a ball of cells. The cells then begin to form groups that develop into different tissues and organs of the body. This developing structure is termed as an embryo.

Q.12. Describe the process of fertilization in human beings.

The first step in the process of reproduction is the fusion of a sperm and an ovum. When sperms come in contact with an egg, one of the sperms may fuse with the egg. Such fusion of the egg and the sperm is called fertilization. During fertilization, the nuclei of the sperm and the egg fuse to form a single nucleus. This results in the formation of a fertilized egg or zygote.

Q.13. Why do fish and frogs lay eggs in hundreds?

Though these animals lay hundreds of eggs and release millions of sperms, all the eggs do not get fertilized and develop into new individuals. This is because the eggs and sperms get exposed to water movement, wind and rainfall. Also, there are other animals in the pond which may feed on eggs. Thus, production of large number of eggs and sperms is necessary to ensure fertilization of at least a few of them.

Q.14. What is the name given to the fusion of male and female gametes?

Fertilization is the name given to the fusion of male and female gametes.

Q.15. What type of asexual reproduction take place in amoeba?

Amoeba reproduces by the common asexual reproduction method called binary fission.