Class 8 Science Textbook Solution

Reproduction in Animals – Class 8 Science Textbook Solution


Chapter 12 Reproduction in Animals
 
1. Explain the importance of reproduction in organisms.
Answer
: Reprodution is very important in the organisms, the continuation of similar kinds of individuals, generation after generation.
 
2. Describe the process of fertilization in human beings.
Answer:
In human beings, the process of fertilization occurs when millions of sperms from the male are transferred into the female body The sperms swim in the oviduct with the help of their tails to reach the egg. When sperms come in contact with the egg than one of the sperms may fuse with the egg and fertilization occurs. A fertilized egg or zygote with a single nuclues is formed which develops into new individual.

 

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.
Answer:
(i) In Female body

(b) A tadpole develops into an adult frog by the process of:
(i) Fertilization
(ii) Metamorphosis
(iii) Embedding
(iv) Budding
Answer:
(ii) Metamorphosis
 
(c) The number of nuclei present in a zygote is:
(i) None
(ii) One
(iii) Two
(iv) Four
Answer:
(iii) Two
 
4. Indicate whether the following statements are True (T) or False (F).
(а) Oviparous animals give birth to young ones.
(b) Each sperm is a single cell.
(c) External fertilization takes place in frog.
(d) A new human individual develops from a cell called gamete.
(e) Egg laid after fertilization is made up of a single cell.
(f) Amoeba reproduces by budding.
(g) Fertilization is necessary even in asexual reproduction.
(h) Binary fission is a method of asexual reproduction.
(i) A zygote is formed as a result of fertilization.
(j) An embryo is made up of a single cell.
Answer:

(a) Oviparous animals give birth to young ones. (F)
(b) Each sperm is a single cell. (T)
(c) External fertilization occurs in frog. (T)
(d) A new human individual develops from a cell. (F)
(e) Egg laid after fertilization is made up of a single cell. (T)
(f) Amoeba reproduces by budding. (F)
(g) Fertilization is necessary even in asexual reproduction. (F)
(h) Binary fission is a method of asexual reproduction. (T)
(i) A zygote is formed as a result of fertilization. (T)
(j) An embryo is made up of a single cell. (F)BA zygote is single celled and no part of the body is identifiable in it whereas a foetus is multicellular and in this all the parts of the body are identifiable.
 
6. Define asexual reproduction. Describe two methods of asexual reproduction in animals.
Answer:
Asexual reproduction is the method of reproduction in which a new individual is produced by a single parent.
Different methods of asexual reproduction are:
•    Binary fission
•    Budding
(a) Binary fission: When one mature cell splits into two daughter cells, the process is called binary fission. In binary fission, first, the nucleus divides into two nuclei. The cytoplasm then divides into two parts each containing a nucleus. Further stretching leads to the formation of the two daughter cells. These cells so formed grow into mature cells and then undergo similar binary fission.
Binary fission in Amoeba is shown below:

 
(b) Budding. Hydra and yeast reproduce by budding. A bulb-like projection formed on the body of an organism is known as the bud. The nucleus of the parent body divides into two, and one of the nuclei goes into the bud. When the bud gets matured, it detaches itself from the parent body and becomes an independent individual.
Reproduction in hydra and yeast by budding is shown below:

 
7. In which female reproductive organ does the embryo get embedded?
Answer:
Embedding of the embryo takes place in the uterus of the female reproductive organ.
 
8. What is metamorphosis? Give example.
Answer:
The drastic change which transforms a larva into an adult is called metamorphosis, e.g., tadpole transforms into a frog. Caterpillar transforms into an adult silkworm.
 
9. Differentiate between internal fertilization and external fertilization.
Answer:
Fertilization that takes place inside the female body is called internal fertilization. This is observed in human beings and other animals such as hens, cows, and dogs. Fertilization that takes place outside the female body is called external fertilization. This is observed in frogs, fish, starfish, etc.
 
10. Complete the crossword puzzle using the hints given below:
Across
1. The process of the fusion of the gametes.
6. The type of fertilization in the hen.
7. The terms used for bulges observed on the sides of the body of Hydra.
8. Eggs are produced here.
Down
2. Sperms are produced in these male reproductive organs.
3. Another term for the fertilization egg.
4. These animals lay eggs.
5. A type of fission in amoeba.


 
Reproduction in Animals Additional s and Answers
 
1. What is reproduction?
Answer:
Reproduction is a process through which young ones are produced.
 
2. Complete the table given below:

3. What is sexual reproduction?
Answer:
Sexual reproduction is the method of reproduction in which a new individual is produced by the fusion of male and female reproductive cells (gametes) produced by the parents.
 
4. What does the male reproductive system consist of?
Answer:
The male reproductive system consists of a pair of testes (singular testis), sperm ducts (sperm tubes), and the penis.
 
5. Show the life-cycle of a frog with the help of a diagram.
Answer:

Eggs → Tadpole larva → Adult frog.
 

6. What is metamorphosis?
Answer:
The drastic change which takes place during the development of an animal is called metamorphosis, e.g tadpole transform into an adult capable of jumping and swimming.
 
7. What is asexual reproduction?
Answer:
Asexual reproduction is the method of reproduction in which a new individual is produced by a single parent. It does not require the involvement of separate sexes.
 
8. Name the methods of asexual reproduction?
Answer:
The methods of asexual reproduction are:
•    Binary fission
•    Budding
 
9. What is cloning?
Answer:
Cloning is the production of an identical cell, any other living part, or a complete organism.

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