NCERT Solutions For Class 8 Science Chapter – 9

NCERT Solutions For Class 8 Science Chapter – 9 Reproduction in Animals

Q1. Explain the importance of reproduction in organisms.

Answer:-

Importance of reproduction in organisms is as follows

Reproduction is termed to be a biological process in which organisms give birth to their offspring
It helps in maintaining the continuity of a particular race and helps in increasing the population of the species.
Reproduction is meant for the survival of all living things.

Q2. Describe the process of fertilisation in human beings.

Answer:-

The process of fertilisation is the meeting of an egg cell from the female and a sperm cell from the male. Basically the fusion of a sperm and an ovum . When sperms come in contact with an egg, one of the spems may fuse with the eggs. Such fusion of the egg and the sperm is called fertilisation.

Fertilisation which takes place inside the female body is called internal fertilisation.

Q3. Choose the most appropriate answer.

Internal fertilisation occurs
In female body.
Outside female body.
In male body.
Outside male body.

Answer:-

In female body

A tadpole develops into an adult frog by the process of
Fertilisation
Metamorphosis
Embedding
Budding

Answer:-

Metamorphosis

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

None
One
Two
Four

Answer:-

(ii)One

Q4. Indicate whether the following statements are True or False.

Oviparous animals give birth to young ones.
Each sperm is a single cell.
External fertilization take place in frog.
A new human individual develops from a cell called gamete.
Egg laid after fertilisation is made up of a single cell.
Amoeba reproduces by budding
Fertilisation is necessary even in asexual reproduction.
Binary fusion is a method of asexual reproduction.
A zygote is formed as a result of fertilisation

Answer:-

True
True
False
True
False
False
True
True

Q5. Give two difference between a zygote and a foetus.

Answer:-

Zygote-

The zygote formed after the fertilisation of male sperm and female ovum.
The zygote divides repeatedly to give rise to a ball of cells. The cells then begin to form groups that develop into different tissues and organs of the body. This developing structure is termed an embryo.

Foetus-

The stage of the embryo in which all the body parts can be identified is called a foetus.
Embryo gradually develops into a foetus.

Q6. Define asexual reproduction . Describe two methods of asexual reproduction in animals.

Answer:-

In this type of reproduction, there is no need for the fusion of male and female gametes. It is a mode of reproduction in which only a single parent is involved is called asexual reproduction.

Two methods of asexual reproduction in animals-

(i)Binary fission – In this type of asexual reproduction, a single cell organism is divided into two halves. Amoeba can reproduce by this method. It begins the process of reproduction by the division of its nucleus into two nuclei. This is followed by the division of its body into two , each part receiving a nucleus finally two amoeba are produced from one parent amoeba.

Binary fission in amoeba

(ii)Budding – In this method developing of new individual is by the bulges and they are called buds formed on the parent body.

These types of asexual reproduction is common in Hydra In hydra the new individuals develop as outgrowths (called buds/) from a single parent. While being attached to the parent, develops into smaller individuals and when these get matured, they detach from the parent and became individual ones.

Budding in hydra

Q7. In which female reproductive organ does not embryo embedded ?

Answer:-

The embryo gets embedded in the wall of the uterus for further development The embryo continues to develop in the uterus It gradually develops bodyparts such as hands , legs , head eyes, ears The stage of the embryo in which all the body parts can be identified is called a foetus.

Q8. What is metamorphosis? Give examples.

Answer:-

Metamorphosis- The biological transformation of the larva into an adult through drastic changes is called metamorphosis.

Example – Life cycle of a toad.

Q9. Differentiate between internal fertilisation and external fertilisation.

Answer:-

Internal fertilisation-

Fertilisations which take place inside the female body is called internal fertilisation
Survival chances of the offspring are more.
Animals including humans cows dogs and hens

External fertilisations-

Fertilisations in which the fusion of a male and a female gamete takes place outside the body of the female is called external fertilisations.
Chance of survival of offspring are less.
It is very common in aquatic animals such as fish, starfish,etc.

Q10. Complete the crossword puzzle using the hints given below.

Across