Solved examples for class 8 science : Chapter 9
Reproduction in Animals
I. Multiple Choice Questions (MCQs).
Q.1. Budding is observed in
Answer. b) Hydra
Q.2. The male reproductive organs consist of
a) a pair of testes
b) two spermatic ducts
c) a penis
d) all of these
Answer. d) all of these
Q.3. Which of the following insect show metamorphosis?
d) Red ant
Ans. (c) Butterfly
Q.4. The female reproductive organs consist of
a) a pair of ovaries
b) a pair of oviduct
c) a pear-shaped uterus
d) all of these
Answer. (d) all of these
Q.5. The middle portion of the sperm contains which provides energy to the sperm for its movement.
d) plasma membrane
Answer. (a) mitochondrion
II. Fill in the blanks by selecting appropriate words from the given list:
List: zygote, fallopian, uterus, embryo, baby, asexual, gametes
Q.1. In……………………………. reproduction only one or a single parent is involved.
Q.2. Like in plants, male and female animals produce………………………….. that fuse together to form a………………………………. .
Q.3. In uterus zygote develops into …………………………. and finally into a…………………………….. .
Q.4. Fertilisation occurs in the…………………………………. tube.
Q.5. The embryo gets embedded in the wall of the…………………………….. for further development.
2- gametes, zygote
3- embryo, baby,
III. Match the items of Column A with those of Column B.
Answer. 1-e, 2-a, 3-d, 4-b, 5-c
IV. Write ‘T’ for the true and ‘F’ for the false statements.
Q.1. The type of reproduction in which one parent organism gets divided into two young ones is called binary fission.
Q.2. For sexual reproduction, male and female reproductive parts are required.
Q.3. The male hormone is responsible for the appearance of primary sexual characters.
Q.4. Through spermatic duct, the sperm passes into fallopian tube of female via penis.
Q.5. The nuclei of sperm and ovum fuse to form a single nucleus, called embryo.
Answer. 1-T, 2-T, 3-F, 4-T, 5-F,
V. Very Short Answer Questions.
1. Name the reproduction in which one parent organism gets divided into two young ones.
Answer: Binary fission.
2. Which hormone is responsible for the appearance of secondary sexual characters in male?
3. Where does zygote develop into embryo and finally into a baby?
4. Name the first step of reproduction in human beings.
5. How is protection of the foetus from the jerk and other injuries possible inside the human uterus?
Answer. Inside the uterus, a layer of liquid called amniotic fluid protects the foetus from jerk and other injuries.
VI. Short Answer Questions.
Q.1. Why is reproduction essential?
Answer. Reproduction essential for continuation of life of animals and it also ensure the similar kinds of individuals, generation after generation.
Q.2. How do son and daughter possess the characters of their parents?
Answer. The nuclei of sperm and ovum fuse to form a single nucleus. This is called zygote. The formation of zygote ensures the beginning of a new individual. Since, a sperm inherits some characters from father and ovum inherits some characters of mother. So, the new individual gets characters from both the father and the mother.
Q.3. How are several protective layers formed around the eggs?
Answer. Soon after fertilisation, zygote divides and redivides and travel down to the oviduct. At that time, several protective layers were formed around the eggs, i.e., a hard shell. After the formation of hard and protective shell, hens lay the eggs.
Q.4. What are kinds of reproduction? Describe asexual reproduction in Hydra through an activity.
Answer. There are two kinds of reproduction:
(i) Asexual reproduction
(ii) Sexual reproduction
There may be one or more buldges developed in the lateral sides of the Hydra.The buldges are called buds. These buds further develop and detach from the parent body and grow into separate individuals of Hydra.
To study asexual reproduction (budding) in Hydra.
Requirements: Permanent slides of budding in Hydra of different stages, microscope, pencil, eraser, paper, etc.
Procedure : Take a permanent slide of Hydra and observe them in a microscope and draw the diagram of it. Repeat this process with other slides. Now, count the number of buldges and their growth in slides that you have seen in different slides and compare it with the given picture.
Q.5. Describe reproduction in Amoeba by binary fission.
Answer. Amoeba is a single celled organism. In this organism, reproduction starts with the division of nucleus, which divides into two nuclei. Nuclear division is followed by division of its body into two. Each part gets a nucleus and finally, two daughter amoebae are produced from one parent Amoeba. So, the type of reproduction in which one parent organism get divided into two young ones is called binary fission.
Q.6. (a) Define viviparous and oviparous animals.
(b) Describe metamorphosis with an example.
Answer (a) Some animals give birth to young ones, are called viviparous animals for example- cow, human, cat, dog, etc. while some other animals which Lay eggs are called oviparous animals for example- hen, birds, etc.
b) After the birth or hatched from the eggs, young ones continue to grow and passes through different stages of their life cycle to become an adult. The life cycle of frog passes through the three distinct states,
$egg \rightarrow tadpole larva \rightarrow adult$. The tadpole transform into adult and capable of jumping and swimming. They also become reproductively mature. The transformation of larva into an adult through different stages of drastic changes is called metamorphosis.
VII. Long Answer Questions.
Q.1. What do you mean by sexual reproduction? Describe human male and female reproductive organs with the help of proper labelled diagrams.
Answer. The mode of reproduction in which two parents are involved to produce their young ones, is called sexual reproduction, in which one is male parent and other is female parent.
The male reproductive organs consist of a pair of testes, two spermatic ducts and a penis. These are called primary sexual organs. The testes produce millions of male gametes called sperms. Through spermatic duct, the sperm passes into fallopian tube of female via penis.
The female reproductive organ consists of a pair of ovaries, a pair of oviduct and a pearshaped uterus.
Q.2. Draw a labelled diagram of a human sperm and explain its function.
Answer: Sperms are very small in size, each has a head, a middle piece and a tail. Sperm is a single cell with only one set of chromosomes. Head part contains nucleus, middle piece contains mitochondrion which provides energy to the sperm for its movement. Testes also produce a chemical substance called male hormone also known as testosterone. This hormone is responsible for the appearance of secondary sexual characters.
Q.3. (a) How does embryo develop in human? Describe with examples.
(b) How is chick completely developed after fertilisation?
Answer. (a) After fertilization, zygote begins to divide and redivide repeatedly to give rise to a ball of cells. Then, cells begin to reorganise and develop into different tissues and organs of the body. This developing structure is known as embryo. The embryo gets embedded in the wall of the uterus for further development. Embryo develops its body parts such as hands, heads, legs, eyes, ears, etc., at this stage embryo is known as foetus. When the development of foetus is complete, the mother gives birth to a baby. The total period of the development of foetus in the uterus is called gestation period. It is about nine months or 40 weeks in case of human.
b) In chick soon after fertilisation, zygote divides and redivides and travel down to the oviduct. At that time, several protective layers were formed around the eggs, i.e., a hard shell. After the formation of hard and protective shell, hens lay the eggs. The development of an embryo into a chick takes about 3 weeks. The hen provides sufficient warmth for the chick embryo development.
This is called incubation. After the chick is completely developed, it hatches out of the egg shell.