Question 1

Question 1Explain the importance of reproduction in organisms.

Accepted Answer

Reproduction is essential for the continuation of a species. It ensures the continuation of similar kinds of individuals, generation after generation and prevents them from becoming extinct.

Question 2

Question 2Describe the process of fertilisation in human beings.

Accepted Answer

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 fertilisation. During fertilisation, the nuclei of the sperm and the egg fuse to form a single nucleus. This results in the formation of a fertilised egg or zygote.

Question 3

Question 3(a)Internal fertilisation occursin female body.outside female body.in male body.outside male body.

Accepted Answer

in female bodyReason — Fertilisation takes place inside the oviduct in the female body. Hence, it is called internal fertilisation.

Question 4

Question 3(b)A tadpole develops into an adult frog by the process offertilisationmetamorphosisembeddingbudding

Accepted Answer

metamorphosisReason — The transformation of the larva into adult through drastic changes is called metamorphosis. The tadpoles look like fish and are capable of swimming and transform into adults capable of jumping and swimming.

Question 5

Question 3(c)The number of nuclei present in a zygote isnoneonetwofour

Accepted Answer

oneReason — During fertilisation, the nuclei of the sperm and the egg fuse to form a single nucleus. This results in the formation of a fertilised egg or zygote.

Question 6

Question 4Indicate whether the following statements are True or False.(a) Oviparous animals give birth to young ones.(b) Each sperm is a single cell.(c) External fertilisation takes place in frog.(d) A new human individual develops from a cell called gamete.(e) Egg laid after fertilisation is made up of a single cell.(f) Amoeba reproduces by budding.(g) Fertilisation is necessary even in asexual reproduction.(h) Binary fission is a method of asexual reproduction.(i) A zygote is formed as a result of fertilisation.(j) An embryo is made up of a single cell.

Accepted Answer

(a) FalseCorrected statement — Viviparous animals give birth to young ones.(b) True(c) True(d) FalseCorrected statement — A new human individual develops from a cell called zygote.(e) True(f) FalseCorrected statement — Amoeba reproduces by binary fission.(g) FalseCorrected statement — Fertilisation is not necessary in asexual reproduction.(h) True(i) True(j) FalseCorrected statement — A zygote is made up of a single cell.

Question 7

Question 5Give two differences between a zygote and a foetus.

Accepted Answer

ZygoteFoetusZygote is formed by the fusion of sperm and egg during fertilisation.Foetus is the stage of the embryo in which all the body parts can be identified.Zygote is unicellular.Foetus is multicellular.

Question 8

Question 6Define asexual reproduction. Describe two methods of asexual reproduction in animals.

Accepted Answer

Asexual reproduction is the type of reproduction in which only a single parent is involved. It takes place by different methods like budding, binary fission etc.Two methods of asexual reproduction in animals are:Budding — In budding, new individuals develop from buds. A bulge or outgrowth appears on the parent's body that goes on to develop into a full organism. It then detaches from the parent and continues to develop into a new individual. Budding is seen in hydra and yeast.Binary Fission — In binary fission, a single-celled organism divides to form two new individuals. The process begins with the division of its nucleus into two nuclei. This is followed by division of its body into two, each part receiving a nucleus. Finally, two cells are produced from one parent cell. It is seen in Amoeba.

Question 9

Question 7In which female reproductive organ does the embryo get embedded?

Accepted Answer

The embryo gets embedded in the wall of the uterus of females for further development.

Question 10

Question 8What is metamorphosis? Give examples.

Accepted Answer

The transformation of the larva into an adult through drastic changes is called metamorphosis. For example, it is seen in frog and butterfly. In frogs, there are three distinct stages, that is, egg, tadpole (larva) and adult. In butterfly the four distinct stages are egg, caterpillar, pupa and adult.

Question 11

Question 9Differentiate between internal fertilisation and external fertilisation.

Accepted Answer

Internal fertilisationExternal fertilisationIt takes place inside the body of female.It occurs outside the body.It is observed in human beings and other animals such as hens, cows and dogs.It is observed in aquatic animals and amphibians such as fish, starfish and frogs.Lesser number of eggs are released.Many more eggs are released.Survival rate is higher.Survival rate is low.

Question 12

Question 10Complete the crossword puzzle using the hints given below.Across1. The process of the fusion of the gametes.6. The type of fertilisation in hen.7. The term used for bulges observed on the sides of the body of hydra.8. Eggs are produced here.Down2. Sperms are produced in these male reproductive organs.3. Another term for in vitro fertilisation.4. These animals lay eggs.5. A type of fission in amoeba.

Accepted Answer

The solution of word puzzle is given below:Across1. Fertilisation.6. Internal.7. Buds.8. Ovary.Down2. Testes.3. IVF.4. Oviparous.5. Binary.

Reproduction in Animals