NCERT Exemplar Solutions Class 8 Science Reproduction in Animals

Multiple Choice Questions..................................

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 

Solution 1: (c) sperm, oviduct, egg, uterus

The male gamete is sperm, the female gamete is egg, and the female reproductive system includes the oviduct and uterus. As a consequence, option c) is a poor combination.

Question 2:  In humans, the development of the fertilised egg takes place in the

(a) ovary

(b) testis

(c) oviduct

(d) uterus 

Solution 2:  (d) uterus

The uterus is where the fertilised egg grows and develops. The embryo is inserted in the uterine wall for implantation and development.

Question 3:  In the list of animals given below, the hen is the odd one out. 

The reason for this is

(a) it undergoes internal fertilisation.

(b) it is oviparous.

(c) it is viviparous.

(d) it undergoes external fertilisation. 

Solution 3:  (b) it is oviparous

The hen is oviparous, meaning she lays the egg and the baby hatches later.

The remaining species are all viviparous. After they have fully grown, they give birth to young ones.

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 is plenty of water.

(c) To ensure a better chance of fertilisation.

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

Solution 4:  (c) To ensure a better chance of fertilization

Since they release gametes into the sea, they have a higher risk of being washed away by water, wind, and rain. Consequently, to increase the likelihood of fertilisation. Animals that use external fertilisation contain a large number of gametes.

Question 5:  Reproduction by budding takes place in

(a) hydra

(c) paramecium

(b) amoeba

(d) bacteria 

Solution 5:  (a) hydra

Binary fission is used by Paramecium, Amoeba, and bacteria to replicate. Hydra reproduces by budding, in which a bud detaches from the parent and develops into a fully formed organism.

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. 

Solution 6:  (d) Fertilisation takes place in the human female.

The vaginal canal is used to inject male gametes into a female's body. Via the oviduct, sperm entering the uterus. A zygote is formed when an egg is fertilised by sperm in the uterus.

Question 7:  In human beings, after fertilisation, the structure which gets embedded in the wall of uterus is

(a) ovum

(b) embryo

(c) foetus

(d) zygote 

Solution 7:  (b) embryo 

The zygote is formed when an egg fuses with sperm and divides into a clump of hundreds of cells, which is the embryo. Implantation is the method of transferring an embryo from the oviduct into the uterus.

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. 

Solution 8:  (b) oviparous with external fertilisation.

Fertilization happens as marine organisms lay eggs and release sperm into the water. External fertilisation refers to the formation of a young person outside of the body.

Question 9: After fertilisation, the resulting cell which gives rise to a new individual is the

(a) embryo

(b) ovum

(c) foetus

(d) zygote 

Solution 9: (d) zygote

The zygote is the first step in the creation of a new person. Any multicellular organism begins life as a single-celled zygote.

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, the zygote

(d) gamete formation, fertilisation, embryo, the zygote 

Solution 10:  (a) gamete formation, fertilisation, zygote, embryo

Male gametes combine with female gametes in the female ovary to fertilise it. Fertilized sperm and eggs combine to create a zygote, which divides several times to form an embryo.

Very Short Answer Questions.......................................

Question 11:  Although two cells called gametes fuse, the product formed is a single cell called the zygote. Justify. 

Solution 11:   Only the nucleus of the sperm is inserted into the uterus during fertilisation to form a zygote. Sperm then degenerates. As a consequence, the fused cell is referred to as a gamete.

Question 12:  Stages in the lifecycle of silkworm are given below. Write them in sequential order.

[Pupa, silkworm, egg, silkmoth] 

Solution 12:

a) Egg

b) Pupa

c) Silkmoth

d) Silkworm

Question 13:  What is the importance of reproduction? 

Solution 13:   The continuity of a species from generation to generation is assured by reproduction.

Question 14:  In markets, eggs of birds are available but never eggs of dogs. Why? 

Solution 14:   Due to the fact that the dog is viviparous. It doesn't contain an egg. It is the mother of a new one.

Question 15:  The eggs of frogs do not have shells for protection, yet they are safe in the water. How? 

Solution 15:   Frog eggs are protected in the water because they have a jelly-like coating on them.

Short Answer Questions.......................................

Question 16:  Fill up the blanks with the terms given below:

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. 

Solution 16:  Amoeba is a single celled organism. It reproduces by asexual reproduction. The process of reproduction begins with the division of its nucleus into two. This is followed by the division of its body into two. This type of reproduction is called binary fission.

Question 17:  The term metamorphosis is not used while describing human development. Why? 

Solution 17:   Since human body parts would be present at birth. Adults' sections vary from those of children during metamorphosis.

Question 18:  Mother gives birth to a baby but the baby has characters of both parents. How is this possible? 

Solution 18:   Fertilization requires the fusion of gametes from both parents, even if the mother gives birth to the child. As a result, all parents build character.

Question 19:  How is reproduction in hydra different from that in amoeba? 

Solution 19:  Hydra reproduces by budding, in which a bud detaches from the parent and develops into a fully formed organism. The amoeba, on the other hand, reproduces by binary fission. The division of the nucleus into two sections starts the reproduction process. The body of the creature is then split into two parts.

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) The 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. 

Solution 20:

1. False- Only in water can external fertilization take place.
2. False- For defence, fish eggs are coated in a jelly-like material.
3. False- Human sperm has three parts: a head, a middle segment, and a tail.
4. True

Question 21:  Why do only male gametes have a tail? 

Solution 21:  Since sperm must be motile in order to penetrate the non-motile egg in the female's ovary.

Question 22:  What does the below figure represent?

Solution 22:  Binary fission of an amoeba with a dividing nucleus is illustrated in the diagram.

Question 23:  Observe the figure and answer the questions that follow.

(a) Label A and B.

(b) Identify the process.

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

Solution 23:

(a) A- sperm

     B- ovum (egg)

(b) The process is fertilisation.

(c) The zygote is formed when the nucleus of the sperm and the nucleus of the egg fuse.

Long Answer Questions.......................................

Question 24:  How can we say that fish exhibits external fertilisation? 

Solution 24:  Female fishes release eggs into the water, while male fishes release sperm. To enter the egg, sperm swim around in the water at random. The sperm nucleus enters the egg and fuses with it to form the zygote. Since fertilisation is done externally. It's referred to as "external fertilisation."

a) Read the following statements and label them in the figure:

1. The part which produces female gametes.
2. The part where the development of the baby takes place.
3. The part through which the developing embryo passes to reach the uterus.

1. Ovary
2. Uterus
3. Oviduct

b) Explain the future development of the embryo that would take place after it gets embedded in the uterus. 

Solution 25:  a)

1. The part which produces female gametes is Ovary
2. The part where the development of the baby takes place is Uterus
3. The part through which the developing embryo passes to reach the uterus is Oviduct 

b) The developing embryo is inserted in the uterine wall to continue its development. In the uterus, the embryo begins to develop. It produces body parts like hands, legs, head, eyes, and ears over time. A foetus is the stage of the embryo in which all of the body parts can be described. The mother gives birth to the baby when the foetus' development is complete.

Question 26:  Hens and frogs are both oviparous exhibiting different types of fertilisation. Explain. 

Solution 26:   Internal fertilisation occurs in hens. The fertilised egg grows inside the female body, but the embryo develops outside the body, resulting in the birth of a chick. In frogs, however, both fertilisation and the growth of the zygote into an embryo and young ones take place outside the body.

Question 27:  Observe the following figures.              

1. Identify the stages (a) to (d) in the given figures during the development of the human baby.
2. Arrange the stages in the correct sequence of development.
3. Explain the development that takes place in any one stage. 

Solution 27:

1.  The stages during the development of the human baby:

(a) The embryo is inserted in the uterus.

(b) The process of fertilisation.

(c) The creation of a zygote and the subsequent growth of an embryo from the zygote.

(d) The nuclei of a zygote have fused.

2.  The correct sequence of stages during development is:

(c) The creation of a zygote and the subsequent growth of an embryo from the zygote.

(b) The process of fertilisation.

(d) The nuclei of a zygote have fused.

(a) The embryo is inserted in the uterus.

3. The nuclei of the sperm and the egg combine to form a single nucleus, resulting in a fertilised egg or zygote.