There are two types of reproduction - sexual and asexual. Some beings are born from eggs, like in ducks and birds. In contrast, some beings like the platypus, humans, etc., give birth to their offspring. There are also ways of reproduction such as cloning, budding, etc. Let’s talk about different types of reproduction:

 

 

 

 

 

Before knowing about the reproduction process, a thorough knowledge of the sexual organs is necessary. In animals, the sexual parts produce gametes. Then, zygotes are formed by the combination of gametes. The zygotes grow into offspring. Sexual reproduction is when male and female gametes combine to create a zygote.

Male reproductive organs:

Testis, sperm ducts, and the penis form the male reproductive parts. Sperms are produced in the testis in innumerable numbers. Every sperm has a head, tail, and middle part.

Female reproductive organs:

In a female, the ovary, oviduct, and uterus are the reproductive parts. The ovaries produce eggs every month. The eggs, when matured, are released from the body. The eggs that are not fused are released from the body along with the skin and blood vessels inside the uterus through menstruation. The sperms and eggs are single cells. The sperms are innumerable, but the egg is only one. 

Fertilisation:

A sperm and an egg fuse through a process called fertilisation. The fusion results in the formation of a zygote, and it has a nucleus. The child inherits properties from both the father and the mother through this process. Usually, fertilisation happens inside the body in the case of hens, humans, etc. This is called internal fertilisation. In frogs, reproduction typically occurs through external fertilisation. They mate during the rainy season and the fertilization happens in water. But all the zygotes formed in fishes or frogs do not survive extreme situations. Only a few are able to survive.

Development of embryo:

The zygote formed as a result of fertilisation continuously divides itself until a cell is formed. It then creates cell groups, tissues, and becomes an embryo. The embryo grows inside the uterus. The stage at which the embryo starts developing organs is called foetus. Embryos develop different layers through stages.

Viviparous and oviparous animals:

Animals that lay eggs are called oviparous, while those which give birth to young ones are called viviparous. Frogs, crocodiles, most fish, etc., lays eggs and are examples of oviparous animals. On the other hand, platypus, seals, humans, etc., are examples of viviparous animals.

Young ones to adults:

In butterflies, caterpillars grow from eggs and undergo various physical changes and growth through different stages called metamorphosis. In a butterfly, the first stage is of an egg. The egg becomes a caterpillar, and the caterpillar becomes a cocoon after some days after reaching its full growth. The cocoon then grows into a beautiful butterfly. Similar is the case of a frog, which starts from an egg. The eggs develop into tadpoles, and the tadpoles grow and become frogs.

Browse the MSVgo resource library for additional information and examples on types of reproduction and metamorphosis to learn concepts in minutes.

Microscopic animals like hydra reproduce by forming buds. Small projections form on the body of a hydra, and these projections separate and grow into a new hydra. This is through the process called budding. Binary fission is responsible for reproduction in amoeba. In this process, the nucleus of an amoeba divides and forms two daughter cells of equal size. These are asexual modes of reproduction where the offspring is directly formed from the parent. 

 Cloning is another technique in which cells are copied to produce a copy of the parent. Dolly the sheep was the first mammal that was cloned. Cloning is usually seen in single-celled organisms like bacteria.

1. Explain the importance of reproduction in organisms

Answer: Reproduction is essential for the existence of life. If there is no reproduction, no offspring would be produced and the organisms would become extinct. Hence, for generations to live, reproduction is necessary.

2. Describe the process of fertilisation in human beings

Answer: In human beings, males and females have different reproductive organs. In males, a pair of testes produces millions of sperms. In females, the ovary produces an egg. These are single cells. These gametes fuse to become a zygote. Which on a further division of cells becomes an embryo. An embryo then grows into a foetus that has organs. This foetus eventually develops into a human baby.

3. Choose the most appropriate answer

(a) Internal fertilisation occurs

(i) in the female body

(ii) outside the female body

(iii) in male body

(iv) outside male body

Answer: Internal fertilisation, like the name itself, suggests that fertilisations happen inside the human body. The sperms enter the woman's body, and it fertilises inside her body. Hence, option (i) in the female body is the correct answer.

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

(i) fertilisation
(ii) metamorphosis
(iii) embedding
(iv) budding

Answer: A tadpole develops into an adult frog by changing its bodily features. A tadpole can exist in water, but with time, it becomes a late tadpole which develops legs and body structures and in the final stage it becomes a frog that can live in water and in land. This happens through the process called metamorphosis. So, option (ii) is the correct answer.

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

(i) none
(ii) one
(iii) two
(iv) four

Answer: A single nucleus is present in the zygote through fusion of male and female gametes. Hence, (ii) one is the right answer.

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

(a) Oviparous animals give birth to young ones

Answer: False, Oviparous are beings that are able to produce offspring by laying eggs. Examples are birds. 

(b) Each sperm is a single cell 

Answer: True, even though millions of sperms are produced from the testis. Each sperm is a single cell. 

(c) External fertilisation takes place in frogs 

Answer: True. In frogs, males and females mate and the zygotes are formed outside the body of the female frog which is then released into the water. 

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

Answer: True, gametes are combined to form zygotes that grow into embryos and foetus. 

(e) Egg laid after fertilisation is made up of a single cell

Answer: True, the single-celled egg then grows into the child.

(f) Amoeba reproduces by budding

Answer: False, hydra reproduces through an asexual process called budding. Amoeba reproduces through binary fission.

(g) Fertilisation is necessary even in asexual reproduction

Answer: False, fertilisation is the process where female and male gametes combine to create a zygote. But in the asexual process, no such phenomenon takes place.

(h) Binary fission is a method of asexual reproduction

Answer: True, binary fission is the process through which amoeba reproduces. It is asexual reproduction.

(i) A zygote is formed as a result of fertilisation. 

Answer: True, zygote is formed as a result of combination between female and male cells. 

(j) An embryo is made up of a single cell

Answer: True, an embryo is a single cell.

5. Give two differences between a zygote and a foetus

Answer: 

•  After the female and male gametes combine, the first stage is the formation of zygote. Foetus is the last stage after embryo. 

• The single celled sperm and egg combine to give unicellular zygotes. Whereas the foetus is multicellular. 

• Zygote, on further division, becomes a foetus. The foetus has organs similar to that of humans.

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

Answer: When the reproduction does not involve fertilisation, it is called asexual reproduction. Hydra reproduces through the asexual process called budding, and amoeba reproduces through binary fission. 

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

Answer: Females have uterus. The embryo formed through fertilisation gets embedded in the uterus. 

8. What is metamorphosis? Give examples.

Answer: Metamorphosis is the change from young to adult form through a series of transformations. 

Examples are frog, butterflies. 

9. Differentiate between internal fertilisation and external fertilisation

Answer: Fertilisation occurs when female and male sex gametes fuse together. This could happen either inside the parent’s body or outside the body. The former is called internal fertilisation and humans, birds etc. are examples of this. The latter is called external fertilisation where the process occurs outside the human body. Frog is an example for this.

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

Across

1. The process of the fusion of the gametes: Fertilisation

6. The type of fertilisation in hen: Internal

7. The term used for bulges observed on the sides of the body of hydra: Buds

8. Eggs are produced here: Ovary

Down

2. Sperms are produced in these male reproductive organs: Testis

3. Another term for in vitro fertilisation: IVF

4. These animals lay eggs: Oviparous

5. A type of fission in amoeba: Binary

 

Reproduction, sexual organs in males and females and types of reproduction are the major portions in class 8 science chapter 9. It also explains internal and external fertilization, reproductive organs in males and females, asexual reproduction, and metamorphosis. A brief concept and examples related to these should be understood clearly. The NCERT class 8 science chapter 9 solutions offered by the MSVgo app will help students grasp the concepts. 

The MSVgo app offers multiple features and services, such as 15,000+ videos and 10,000+ questions bank developed in accordance with the NCERT syllabus and the boards of CBSE, ICSE, IGCSE, and ISC, textbook question video solutions, solutions matched to all textbooks and also quizzes to test your knowledge.

With the app, you may save your notes and share them with your friends. You can also participate in the MSVgo Interschool Challenge to represent your school on a nationwide scoreboard.