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Thursday, 10 August 2017

Class 8th : Science - Chapter 4 : Reproduction in Animals

Reproduction_in_Animals_Science_8th_Chapter_4
Chapter 4: Reproduction in Animals

EXERCISES
1. Explain the importance of reproduction in organisms.
Ans. Reproduction is very important in organisms as it ensures the continuation of similar kinds of individuals, generation after generation.

2. Describe the process of fertilization in human beings.
Ans. The fusion of the egg and the sperm inside the female body of a human being is known as fertilization. The fusion of the nuclei of these gametes results in the formation of zygote with nuclei.
3. Choose the most appropriate answer:
(a) Internal fertilization occurs
(i) in female body.
(ii) outside female body.
(iii) in male body.
(iv) outside male body.
Ans. (i) In female body
(b) A tadpole develops into an adult frog by the process of
(i) fertilization. (ii) metamorphosis. (iii) embedding. (iv) budding.
Ans. (ii) Metamorphosis
(c) The number of nuclei present in a zygote is
(i) none. (ii) one. (iii) two. (iv) four.
Ans. (ii) One
4. Indicate whether the following statements are True (T) or False (F):
(a) Oviparous animals give birth to young ones. ( )
Ans. False
(b) Each sperm is a single cell. ( )
Ans. True
(c) External fertilization takes place in frog. ( )
Ans. True
(d) A new human individual develops from a cell called gamete. ( )
Ans. False
(e) Egg laid after fertilization is made up of a single cell. ( )
Ans. True
(f) Amoeba reproduces by budding. ( )
Ans. False
(g) Fertilization is necessary even in asexual reproduction. ( )
Ans. False
(h) Binary fission is a method of asexual reproduction. ( )
Ans. True
(i) A zygote is formed as a result of fertilization. ( )
Ans. True
(j) An embryo is made up of a single cell. ( )
5. Give two difference between a zygote and a foetus.
Ans. Zygote: It consist of single cell. It is formed after the fertilization of gametes.
Foetus: It is the stage which identifies all the parts of embryo. It consists of multiple cells.
6. Define asexual reproduction. Describe two methods of asexual reproduction in animals.
Ans. The type of reproduction in which only a single parent is involved is called asexual reproduction.
Two methods of asexual reproduction:
1. Budding: In this type of asexual reproduction, the individuals develop from the buds. Eg. Hydra.
2. Binary fission: In this type of reproduction, the nuclei of a cell divides into two nuclei followed their division into two more nuclei resulting in the formation of an individual with one nucleus. Eg. Amoeba
7. In which female reproductive organ does the embryo get embedded?
Ans. Foetus
8. What is metamorphosis? Give examples.
Ans. The transformation or change of larva in to an adult through drastic changes is called metamorphosis. Eg. Frog, Insects
9. Differentiate between internal fertilization and external fertilization.
Ans. Internal Fertilization: It takes place inside the female body. It occurs in many animals including humans, cows, dogs and hens.
External Fertilization: In this, the fertilization of gametes takes place outside the female body. It is very common in aquatic animals such as fish, starfish, frogs etc.
10. Complete the crossword puzzle using the hints given below
Across
1. The process of the fusion of the gametes. FERTILIZATION
6. The type of fertilization in hen. INTERNAL
7. The term used for bulges observed on the sides of the body of Hydra. BUDS
8. Eggs are, produced here. OVERY
Down
2. Sperms are, produced in these male reproductive organs. TESTES
3. Another term for the fertilized egg. ZYGOTE
4. These animals lay eggs. OVIPAROUS

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