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Chapter 9: Cell - Reproduction in Animals



   Chapter 9: Cell - Reproduction in Animals

  Class: VIII

   Exemplar Solutions


Question 1

 Sets of reproductive terms are given below.

Choose the set that has an incorrect combination.

(a) sperm, testis, sperm duct, penis

 (b) menstruation, egg, oviduct, uterus

(c) sperm, oviduct, egg, uterus

(d) ovulation, egg, oviduct, uterus

Answer 1 (c)

Question 2

 In humans, the development of fertilised egg takes place in the

 (a) ovary   (c) oviduct

 (b) testis   (d) uterus

Answer 2 (d)

Question 3

In the list of animals given below, hen is the odd one out.

   human being, cow, dog, hen

The reason for this is

(a) it undergoes internal fertilisation.

(b) it is oviparous.

(c) it is viviparous.

 (d) it undergoes external fertilisation.

Answer 3 (b)

Question 4

 Animals exhibiting external fertilisation produce a large number of gametes.

Pick the appropriate reason from the following.

(a) The animals are small in size and want to produce more offsprings.

(b) Food is available in plenty in water.

(c) To ensure better chance of fertilisation.

(d) Water promotes production of large number of gametes.

Answer 4 (c)

Question 5

 Reproduction by budding takes place in

(a) hydra  (c) paramecium

(b) amoeba  (d) bacteria

Answer 5 (a)

Question 6

 Which of the following statements about reproduction in humans is correct?

(a) Fertilisation takes place externally.

 (b) Fertilisation takes place in the testes.

(c) During fertilisation egg moves towards the sperm.

 (d) Fertilisation takes place in the human female.

Answer 6 (d)

Question 7

 In human beings, after fertilisation, the structure which gets embedded in the wall of uterus is

(a) ovum  (c) foetus

 (b) embryo  (d) zygote

Answer 7 (b)

Question 8

 Aquatic animals in which fertilisation occurs in water are said to be:

 (a) viviparous without fertilisation.

(b) oviparous with external fertilisation.

 (c) viviparous with internal fertilisation.

(d) oviparous with internal fertilisation.

Answer 8 (b)

Question 9

 After fertilisation, the resulting cell which gives rise to a new individual is the

 (a) embryo  (c) foetus

 (b) ovum  (d) zygote

Answer 9 (d)

Question 10

 In human beings, the correct sequence of events during reproduction is

 (a) gamete formation, fertilisation, zygote, embryo

(b) embryo, zygote, fertilisation, gamete formation

(c) fertilisation, gamete formation, embryo, zygote

(d) gamete formation, fertilisation, embryo, zygote

Answer 10 (a)


Question 11

 Although 2 cells called gametes fuse, the product formed is a single cell called zygote. Justify.

Answer 11

 During fertilisation, only the nucleus of the sperm moves into the egg cell and fuses with the egg nucleus to form the zygote. The sperm degenerates.

Question 12

 Stages in the lifecycle of silkworm are given below. Write them in sequential order.

   pupa, silkworm, egg, silkmoth

Answer 12

egg, caterpiller, pupa, silk moth

Question 13

 What is the importance of reproduction?

Answer 13

It ensures the continuation of species generation after generation.

Question  14

 In markets, eggs of birds are available but never eggs of dogs. Why?

Answer 14

Dogs do not lay eggs.

Question 15

 The eggs of frogs do not have shells for protection, yet they are safe in water. How?

Answer 15

A layer of jelly covers the eggs of frog and provides protection.


Question 16

Fill up the blanks with the terms given below:

body, asexual, binary, single, nucleus  

Amoeba is a ___________ celled organism. It reproduces by ___________ reproduction. The process of reproduction begins by the division of its ___________ into two. This is followed by the division of its ___________ into two. This type of reproduction is called ___________ fission.

Answer 16

Single, asexual, nucleus, body, binary

Question 17

 The term metamorphosis is not used while describing human development. Why?

Answer 17

In human beings, body parts of an adult are present from the time of birth itself. Whereas, in metamorphosis, the parts of the adult are different from those at the time of birth.

Question 18

 Mother gives birth to a baby but the baby has characters of both parents. How is this possible?

Answer 18

Although mother gives birth to a child, fertilisation involves two gametes, one from the mother and the other from father. The zygote, therefore has both father and mother’s contribution. Since the zygote develops into the baby it has characters of both parents.

Question 19

How is reproduction in hydra different from that in amoeba?

Answer 19

Hydra reproduces by budding where an outgrowth arises from the parent and develops into a new individual. Amoeba reproduces by binary fission in which the division of nucleus is followed by division of the cell resulting in two individuals.

Question 20

 State whether the following statements are True or False. If false, correct the statement:

(a) External fertilisation can occur both in water and on land.

(b) The eggs of fish are covered by hard shells for protection.

(c) Human egg has a head, middle piece and tail.

(d) In adult human females, a single mature egg is released into an oviduct every month.

Answer 20

(a) F; External fertilisation occurs only in water.

(b) F; The eggs of fish are covered by a jelly for protection.

(c) F; Human sperm has a head, middle piece and tail.

(d) T

Question 21

Why do only male gametes have a tail?

Answer 21

Because they have to be motile and reach the non-motile female gamete.

Question 22

 What does Fig. 9.1 represent?

Science Class 8 Chapter 9 Exemplar

Answer 22

The figure shows an amoeba undergoing binary fissions with a dividing nucleus.

Question 23

Observe the figure given as Fig. 9.2 and answer the questions that follow.

Science Class 8 Chapter 9 Exemplar

(a) Label A and B.

(b) Identify the process.

 (c) What happens during this process and what is formed?

Answer 23

(a) A-sperm; B-ovum (egg)

(b) Fertilisation

(c) Sperm nucleus fuses with the egg nucleus to form the zygote.


Question 24

How can we say that fish exhibits external fertilisation?

Answer 24

Female fish release eggs into water and male fish releases sperms. Sperms swim randomly in water and comes in contact with the eggs. The nucleus of the sperm moves into the egg and fuses with it. Since fertilisation occurs in water, outside the female body, it is external fertilisation.

Question 25

After observing Fig. 9.3 answer the following.

Science Class 8 Chapter 9 Exemplar

  1. Read the following statements and label them in the figure:
  • The part which produces female gametes.
  • The part where development of the baby takes place.
  • The part through which the developing embryo passes to reach the uterus.
  1. Explain the future development of the embryo that would take place after it gets embedded in the uterus.

Answer 25

Science Class 8 Chapter 9 Exemplar

Question 26

Hens and frogs are both oviparous exhibiting different types of fertilisation. Explain.

Answer 26

Hens are oviparous in which internal fertilisation takes place. The fertilised egg develops into an embryo inside the body. However, the development of chick from the embryo takes place outside the body.

Frogs are oviparous in which both fertilisation and development of zygote to embryo and young ones occurs outside the body.

Question 27

 Observe the following figures.

Science Class 8 Chapter 9 Exemplar

Science Class 8 Chapter 9 Exemplar

Science Class 8 Chapter 9 Exemplar

  • Identify the stages a to d in Fig. 9.4 during development of human baby.
  • Arrange the stages in correct sequence of development.
  • Explain the development that takes place in any one stage.

Answer 27

 (i) (a) Embedding of the embryo in the uterus.

 (b) Fertilisation.

 (c) Zygote formation and development of an embryo from the zygote.

 (d) Zygote showing fusion of nuclei.

 (ii) The correct sequence is c, b, d, a

(iii) Zygote formation The sperm and the egg nuclei fuses to form a single nucleus resulting in the formation of a fertilised egg or zygote. (Note: One step is explained as an example. Students may explain any other step.)

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