Reproduction in Animals NCERT Solutions for Class 8

 

Reproduction in Animals is an essential unit of the Class 8 Science syllabus and students must prepare it thoroughly. Students can visit the NCERT solutions of Reproduction in Animals prepared by the subject-matter experts by SimplyAcad. The study material is crafted to assist students in gaining in-depth knowledge of the theories that the chapter discusses.

Access NCERT Solutions of Class 8 Reproduction in Animals

1. Explain the importance of reproduction in organisms.

Solution:

The following highlights the significance of reproduction in organisms:

The biological process by which organisms give birth to their progeny is referred to as reproduction.

It contributes to both the expansion of the species’ population and the preservation of a certain race.

All organisms are supposed to reproduce to survive.

2. Describe the process of fertilization in human beings.

Solution:

The process of male and female gametes fusing is known as fertilization.

The male reproductive organ known as the penis releases the male gametes or sperm.

Through the vagina, the sperm are released and enter the female body.

Sperm exit the vagina and pass through the fallopian tubes to encounter eggs.

After that, the fallopian tube is used for the fertilization process.

A zygote is created when the female and male gamete cells—egg and sperm—fuse.

After around five days, the zygote rapidly divides to create a collection of cells known as a morula, which eventually forms the embryo. After fertilization, the fetus is present for roughly eight weeks.

3. Choose the most appropriate answer.

(a) Internal fertilization occurs

(i) in the female body

(ii) outside the female body

(iii) in the male body

(iv) outside male body

(b) A tadpole develops into an adult frog by the process of

(i) fertilization

(ii) metamorphosis

(iii) embedding

(iv) budding

(c) The number of nuclei present in a zygote is

(i) none

(ii) one

(iii) two

(iv) four

Solution:

a) (i) in the female body

b) (ii) metamorphosis

c) (iii) two

4. Indicate whether the following statements are True (T) or False (F).

(a) Oviparous animals give birth to young ones. ( )

(b) Each sperm is a single cell. ( )

(c) External fertilization takes place in the frog. ( )

(d) A new human individual develops from a cell called a gamete. ( )

(e) The 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. ( )

Solution:

a) False

b) True

c) True

d) False

e) True

f) False

g) False

h) True

i) True

j) False

5. Give the differences between a zygote and a fetus.

Solution:

Zygote:

It is the initial phase of growth.

The union of male and female gametes forms it.

There is just one cell.

A multiplex zygote splits into an embryo.

After a week, the zygote usually matures into the following stage.

Fetus

It is the final phase of an organism’s development.

All of the primary identifiable body parts of a fully grown creature are visible at the embryonic stage.

Following the embryonic stage is the fetus stage.

The fetus primarily develops internally.

6. Define asexual reproduction. Describe two methods of asexual reproduction in animals. \section*

{Solution} \textbf{Asexual Reproduction:} Asexual reproduction is a mode of reproduction in which only a single parent is involved, and there is no formation and fusion of gametes. This type of reproduction results in offspring that are genetically identical to the parent. \textbf{Methods of Asexual Reproduction:} 1. **Binary Fission:** In binary fission, a single parent cell divides into two daughter cells. The nucleus of the parent cell divides first, followed by the division of the cytoplasm, resulting in the formation of two daughter cells. This type of reproduction is common in primitive organisms, such as the amoeba. During binary fission, the genetic material is equally distributed between the two daughter cells, ensuring that they are genetically identical to the parent. 2. **Budding:** Budding is a form of asexual reproduction observed in organisms like Hydra. In this process, a small outgrowth called a bud develops on the parent organism. The bud grows and eventually forms structures such as tentacles and a mouth, similar to those of the parent Hydra. Once the bud has fully developed, it detaches from the parent body and grows into a new individual. The new individual is genetically identical to the parent.

7. In which female reproductive organ does the embryo get embedded?

Solution:

The uterus is where the embryo attaches itself to the female reproductive organ.

As soon as it attaches, body components including hands, eyes, and legs begin to form.

We then refer to the embryo as a fetus.

8. What is metamorphosis? Give two examples of metamorphosis. \section*

{Solution} \textbf{Metamorphosis:} Metamorphosis is the process of transformation in which an animal undergoes a series of distinct developmental stages, changing from an immature form, such as a larva, to an adult form. This process often involves significant changes in the animal’s morphology, physiology, and behavior. \textbf{Examples of Metamorphosis:} 1. **Frogs:** Frogs undergo metamorphosis in which they transition from a water-dwelling tadpole, which has gills and a tail, to an air-breathing adult frog with lungs and limbs. The tadpole’s body structure changes dramatically during this process, including the development of legs and the absorption of the tail. 2. **Silk Moths:** Silk moths exhibit complete metamorphosis, progressing through four stages: egg, larva (caterpillar), pupa (cocoon), and adult moth. The larval stage involves feeding and growth, while the pupal stage is a period of reorganization, during which the larva transforms into the adult moth, emerging with wings and reproductive organs.

9. Differentiate between internal fertilization and external fertilization.

Solution:

Fertilization, in general, is defined as the fusion of a male and a female gamete.

Internal fertilization

It takes place within the female anatomy.

The likelihood of the progeny surviving is high.

By internal fertilization, the fertilized egg or embryo is shielded from unfavorable conditions.

A cow, a human, a dog, a monkey, etc. are examples.

External fertilization

Outside of the female body, it happens.

The chances of the progeny surviving are slim.

This kind of fertilization is used by the majority of aquatic species, and because of external dangers, it has the benefit of producing a large number of progeny.

Fish, frogs, and other species are examples.

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 a hen.

7. The term is used for bulges observed on the sides of the body of a hydra.

8. Eggs are produced here.

Down

2. Sperms are produced in these male reproductive organs.

3. Another term for in vitro fertilization.

4. These animals lay eggs.

5. A type of fission in amoeba

Across

1) Fertilization

6) Internal

7) Buds

8) Ovary

Down

2) Testis

3) Zygote

4) Oviparous

5) Binary