Class 8 Science · 26 questions · 26 with answers
Sets of reproductive terms are given below. Choose the set that has an incorrect combination.
(c) sperm, oviduct, egg, uterus
In humans, the development of fertilised egg takes place in the
(d) uterus
In the list of animals given below, hen is the odd one out. human being, cow, dog, hen The reason for this is
(b) it is oviparous.
Animals exhibiting external fertilisation produce a large number of gametes. Pick the appropriate reason from the following.
(c) To ensure better chance of fertilisation.
Reproduction by budding takes place in
(a) hydra
Which of the following statements about reproduction in humans is correct?
(d) Fertilisation takes place in the human female.
In human beings, after fertilisation, the structure which gets embedded in the wall of uterus is
(b) embryo
Aquatic animals in which fertilisation occurs in water are said to be:
(b) oviparous with external fertilisation.
After fertilisation, the resulting cell which gives rise to a new individual is the
(d) zygote
In human beings, the correct sequence of events during reproduction is
(a) gamete formation, fertilisation, zygote, embryo
Although 2 cells called gametes fuse, the product formed is a single cell called zygote. Justify.
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.
Stages in the lifecycle of silkworm are given below. Write them in sequential order. pupa, silkworm, egg, silkmoth
egg, caterpiller, pupa, silk moth
What is the importance of reproduction?
It ensures the continuation of species generation after generation.
In markets, eggs of birds are available but never eggs of dogs. Why? REPRODUCTION IN ANIMALS 49
Dogs do not lay eggs.
The eggs of frogs do not have shells for protection, yet they are safe in water. How?
A layer of jelly covers the eggs of frog and provides protection. SHORT ANSWER QUESTIONS
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.
Single, asexual, nucleus, body, binary
The term metamorphosis is not used while describing human development. Why?
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.
Mother gives birth to a baby but the baby has characters of both parents. How is this possible?
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.
How is reproduction in hydra different from that in amoeba?
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. ANSWERS 133
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.
Why do only male gametes have a tail?
Because they have to be motile and reach the non-motile female gamete.
What does Fig. 9.1 represent? Fig. 9.1
This question refers to a figure in the original PDF.
The figure shows an amoeba undergoing binary fissions with a dividing nucleus.
Observe the figure given as Fig. 9.2 and answer the questions that follow. 50 E XEMPLAR PROBLEMS Fig. 9.2
This question refers to a figure in the original PDF.
(a) Label A and B.
(b) Identify the process.
(c) What happens during this process and what is formed?
How can we say that fish exhibits external fertilisation? 25. Fig. 9.3 REPRODUCTION IN ANIMALS 51 After observing Fig. 9.3 answer the following. a. Read the following statements and label them in the figure:
This question refers to a figure in the original PDF.
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.
Hens and frogs are both oviparous exhibiting different types of fertilisation. Explain.
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. 134 E XEMPLAR PROBLEMS Frogs are oviparous in which both fertilisation and development of zygote to embryo and young ones occurs outside the body.
Observe the following figures.
This question refers to a figure in the original PDF.
(a)
(b) 52 E XEMPLAR PROBLEMS
(c)
(d) Fig. 9.4 (i) Identify the stages a to d in Fig. 9.4 during development of human baby. (ii) Arrange the stages in correct sequence of development. (iii) Explain the development that takes place in any one stage.