GSEB Class 8 Science Solutions Chapter 9 Reproduction in Animals

Question 1. Explain the importance of reproduction in organisms.
Answer: Reproduction is a really vital process for all living beings. This process is important for keeping a species going and ensuring its continued existence on Earth.
In simple words: Reproduction is very important. It helps different kinds of living things keep existing and prevents them from disappearing.

Exam Tip: When explaining importance, focus on both individual survival (though less direct) and species continuation, which is the primary biological role.

Question 2. Describe the process of fertilisation in human beings.
Answer: Sexual reproduction occurs in humans. Internal fertilisation happens within human bodies. Males release sperm inside the female's body. Sperm and ovum then join together in the fallopian tube to create a zygote. During this process, the nucleus of the sperm merges with the nucleus of the ovum to create a single nucleus. This entire series of events is known as fertilisation.
In simple words: Humans reproduce sexually. Inside the female's body, sperm and egg combine in the fallopian tube to form a zygote. This fusion of nuclei is called fertilisation.

Exam Tip: Key terms to include are "sexual reproduction," "internal fertilisation," "sperm," "ovum," "fallopian tube," "zygote," and "fusion of nuclei."

Question 3. Choose the most appropriate answer:
(a) Internal fertilisation occurs
(i) in female body
(ii) outside female body
(iii) in male body
(iv) outside male body.
(b) A tadpole develops into an adult frog by the process of
(i) fertilisation
(ii) metamorphosis
(iii) embedding
(iv) budding.
(c) The number of nuclei present in a zygote is
(i) none
(ii) one
(iii) two
(iv) four
Answer:
(a) (i) in female body
(b) (ii) metamorphosis
(c) (ii) one.
In simple words: Internal fertilisation takes place inside the female. Tadpoles become frogs through metamorphosis. A zygote has one nucleus.

Exam Tip: Remember specific definitions: internal fertilisation happens inside the body, metamorphosis is a major change from larva to adult, and a zygote is a single cell with one fused nucleus.

Question 4. Indicate whether the following statements are True or False.
(a) Oviparous animals give birth to young ones.
(b) Each sperm is a single cell.
(c) External fertilisation takes place in frog.
(d) A new human individual develops from a cell called gamete.
(e) Egg laid after fertilisation is made up of a single cell.
(f) Amoeba reproduces by budding.
(g) Fertilisation is necessary even in asexual reproduction.
(h) Binary fission is a method of asexual reproduction.
(i) A zygote is formed as a result of fertilisation.
(j) An embryo is made up of a single cell.
Answer:
(a) False
(b) True
(c) True
(d) False
(e) True
(f) False
(g) False
(h) True
(i) True
(j) False
In simple words: Oviparous animals lay eggs, not give birth. A sperm is one cell. Frogs have external fertilisation. A gamete is not a whole new individual. A fertilised egg starts as one cell. Amoeba uses binary fission, not budding. Asexual reproduction does not need fertilisation. Binary fission is a type of asexual reproduction. A zygote is made when fertilisation happens. An embryo has many cells.

Exam Tip: Thoroughly understand the definitions of key terms like "oviparous," "gamete," "zygote," "embryo," "fertilisation," "asexual reproduction," "budding," and "binary fission."

Question 5. Give two differences between a zygote and a foetus.
Answer:
Zygote:
• It contains only a single cell.
• It is formed by the joining of ovum and sperm.
Foetus:
• It contains many cells.
• It is formed by repeated cell divisions of a zygote.
In simple words: A zygote is a single cell made when sperm and egg join. A foetus has many cells and grows from a zygote that keeps dividing.

Exam Tip: Emphasise the developmental stage: zygote is the initial single cell, while a foetus is a much later, multi-cellular stage with developing organs.

Question 6. Define asexual reproduction. in animals.
Answer: The kind of reproduction where only one parent is involved is known as asexual reproduction. Asexual reproduction happens in animals through different techniques:
(i) Budding: This activity occurs in hydra and yeast. A part of the organism starts growing outwards. Slowly, it grows and becomes a separate individual.
(ii) Binary Fission: This kind of reproduction occurs in amoeba. The nucleus of the amoeba separates into two, followed by the division of their bodies, with each part getting one nucleus. Each new part develops into a separate amoeba. This form of reproduction is common among unicellular organisms.
In simple words: Asexual reproduction means only one parent is needed to make new offspring. It happens in ways like budding, where a new part grows off the parent (like in hydra), or binary fission, where one cell splits into two (like in amoeba).

Exam Tip: Define asexual reproduction clearly and then provide specific examples with a brief description of each process, focusing on key organisms like hydra and amoeba.

Question 7. In which female reproductive organ does the embryo get embedded?
Answer: In the uterus.
In simple words: The embryo gets attached and grows in the uterus.

Exam Tip: Remember that the uterus is the specific organ where the embryo implants and develops.

Question 8. What is metamorphosis? Give examples.
Answer: The change of a larva into an adult through significant modifications is called metamorphosis. For instance, in a frog and a butterfly, you can see this process.
In simple words: Metamorphosis is when a young animal (like a larva) changes a lot to become an adult. Frogs and butterflies are good examples.

Exam Tip: Highlight the "drastic changes" and the transition from "larva to adult" in your definition, and remember to provide at least two common examples.

Question 9. Differentiate between internal fertilisation and external fertilisation.
Answer: Internal fertilisation happens inside the female's body, while external fertilisation occurs outside the female's body. In internal fertilisation, the male releases sperm into the female's body, but in external fertilisation, sperm are released openly, usually in water.
In simple words: Internal fertilisation means sperm and egg join inside the female's body. External fertilisation means they join outside the female's body, often in water.

Exam Tip: The main distinction is the location where the fusion of gametes takes place – inside or outside the female body. Mentioning the medium (e.g., water) for external fertilisation is also helpful.

Question 10. Complete the crossword puzzle using the hints given below:
Across:
1. The process of the fusion of the gametes.
6. The type of fertilisation in hen.
7. The term 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 in vitro fertilization.
4. These animals lay eggs.
5. A type of fission in amoeba.
Answer:

Exam Tip: For crossword puzzles, always read all hints carefully for both "Across" and "Down" categories. Start with the easiest clues or those with fewer possible answers to fill in initial letters, which then help solve more difficult clues.