Question and Answer:

Question 1.
Why is reproduction essential for organisms?
Answer:
Reproduction is essential for organisms because it ensures the continuity of a species from one generation to the next. Without reproduction, individuals would die without leaving offspring, leading to the extinction of that species. It also helps in the transmission of genetic material, maintaining population stability, and allowing variations that contribute to evolution and adaptation.

Question 2.
Which is a better mode of reproduction: sexual or asexual? Why?
Answer:
Sexual reproduction is considered a better mode of reproduction than asexual reproduction because it introduces genetic variation among offspring. These variations help species adapt to changing environmental conditions and increase their chances of survival and evolution.

In contrast, asexual reproduction produces genetically identical offspring (clones), which limits adaptability and makes the species more vulnerable to diseases and environmental changes.

Question 3.
Why is the offspring formed by asexual reproduction referred to as clone?
Answer:
The offspring formed by asexual reproduction is referred to as a clone because it is genetically identical to the parent organism. Since asexual reproduction involves only one parent and no fusion of gametes, there is no genetic variation in the offspring. As a result, all individuals produced are exact copies of the parent in terms of their genetic makeup.

Question 4.
Offspring formed due to sexual reproduction have better chances of survival. Why? Is this statement always true?
Answer:
The progeny formed after asexual reproduction are exact copies of their parents. But in sexual reproduction, the male and female gametes produced from different parents fuse to produce progeny that show morphological and genetic variations from their parents.

These variations improve the chances of survival of the offspring in changing environmental conditions.

However, this statement is not always true, because in stable environments, asexual reproduction can also be advantageous as it is faster and produces many offspring without the need for gamete fusion.

Question 5.
How does the progeny formed from asexual reproduction differ from those formed by sexual reproduction?
Answer:
The progeny formed from asexual reproduction are genetically identical to the parent because there is no fusion of gametes and only one parent is involved. Such offspring are called clones.

In contrast, the progeny formed from sexual reproduction show genetic variation because they are produced by the fusion of male and female gametes from two parents. These variations make each offspring genetically unique and better adapted to survive in changing environments.

Question 6.
Distinguish between asexual and sexual reproduction. Why is vegetative reproduction also considered as a type of asexual reproduction?
Answer:

Question 7.
What is vegetative propagation? Give two suitable examples.
Answer:
Vegetative propagation is a type of asexual reproduction in which new plants are formed from the vegetative parts of a plant such as roots, stems, leaves, or buds, without the involvement of gametes or seeds.

Examples:

1. Potato – New plants arise from the eyes (buds) present on the potato tuber.
2. Bryophyllum – New plantlets develop from the notches present on the margins of leaves.

Question 8.
Define
(a) Juvenile phase,
(b) Reproductive phase,
(c) Senescent phase.
Answer:
(a) Juvenile phase: It is the period of growth between birth and reproductive maturity. In plants, it is the vegetative phase that ends with the formation of reproductive structures.

(b) Reproductive phase: It is the phase that begins after the juvenile phase, during which organisms produce gametes or flowers for reproduction.

(c) Senescent phase: It is the period between reproductive maturity and death, characterized by gradual deterioration in physiological activities.

Question 9.
Higher organisms have resorted to sexual reproduction in spite of its complexity. Why?
Answer:
Higher organisms have resorted to sexual reproduction in spite of its complexity because it offers several important advantages:

1. It introduces genetic variation through the recombination of genes from two parents.
2. This variation helps species to adapt better to changing environmental conditions.
3. It promotes evolution and helps in the formation of new species.
4. It eliminates harmful mutations over generations.

Hence, sexual reproduction ensures greater survival and evolutionary success of species compared to asexual reproduction.

Question 10.
Explain why meiosis and gametogenesis are always interlinked?

Answer:

• In sexually reproducing organisms, meiosis occurs during gametogenesis to reduce the diploid number of chromosomes (2n) to the haploid number (n) in the gametes.
• This reduction is essential so that during fertilization, the fusion of male and female gametes restores the diploid chromosome number in the zygote.
• Thus, meiosis and gametogenesis are always interlinked because meiosis ensures the formation of haploid gametes necessary for maintaining chromosomal stability across generations.

Question 11.
Identify each part in a flowering plant and write whether it is haploid (n) or diploid (2n).

• Ovary
• Anther
• Egg
• Pollen
• Male gamete
• Zygote

Answer:

Question 12.
Define external fertilisation. Mention its disadvantages.
Answer:
External fertilisation is the process in which fusion of male and female gametes occurs outside the body of the organism, usually in an external medium like water (e.g., in frogs and fishes).

Disadvantages:

1. A large number of gametes are wasted as not all meet and fuse.
2. There is a high risk of predation of gametes and young ones.
3. Environmental factors such as temperature and water currents can affect fertilisation success.
4. Offspring survival rate is very low due to lack of parental care.

Question 13.
Differentiate between a zoospore and a zygote.
Answer:

Question 14.
Differentiate between gametogenesis from embryogenesis.
Answer:

Question 15.
Describe the post-fertilisation changes in a flower.
Answer:
After fertilisation, the following post-fertilisation changes occur in a flower:

1. The petals, sepals, stamens, style, and stigma usually wither and fall off. In some cases, sepals remain persistent (e.g., pea).
2. The zygote develops into an embryo.
3. The fertilised ovule develops into a seed.
4. The wall of the ovary develops into the fruit wall, called the pericarp.
5. The ripened ovary containing the pericarp and seeds is called a fruit.

Question 16.
What is a bisexual flower? Collect five bisexual flowers from your neighbourhood and with the help of your teacher find out their common and scientific names.
Answer:
A bisexual flower is a flower in which both the sex organs – androecium (male) and gynoecium (female) are present. Such flowers can produce both pollen and ovules.

Examples of bisexual flowers:

Question 17.
Examine a few flowers of any cucurbit plant and try to identify the staminate and pistillate flowers. Do you know any other plant that bears unisexual flowers?
Answer:
In cucurbit plants, two types of unisexual flowers are present:

• Staminate flowers: These flowers contain stamens (male reproductive organs) but lack pistils. They do not produce fruits.
• Pistillate flowers: These flowers contain pistils (female reproductive organs) but lack stamens. They develop into fruits after fertilisation.

Examples of plants with unisexual flowers:

• Papaya (Carica papaya)
• Date palm (Phoenix dactylifera)

Question 18.
Why are offspring of oviparous animals at a greater risk as compared to offspring of viviparous animals?
Answer:
In oviparous animals, the development of the zygote takes place outside the body of the female parent, whereas in viviparous animals, it occurs inside the mother’s body.
In oviparous animals, the fertilised eggs are laid in the open environment, where they are not protected from predators and environmental hazards.

Therefore, their survival rate is very low as compared to the offspring of viviparous animals, which are protected and nourished within the mother’s body until birth.