CBSE Board Class XII – NCERT Biology
Chapter 1, Reproduction in Organisms
(NCERT solutions of Class 12 Biology textbook chapter exercise questions)
To see answers of Question 1 – 9 please
click below
Question
10: Explain why meiosis and gametogenesis are always interlinked.
Answer: Meiosis occurs at gametogenesis
stage in diploid organisms during gamete formation. As a result, the gametes
become haploid. By the fusion of two such haploid gametes, a diploid zygote is
formed, and it develops involving mitotic divisions. Thus, meiosis maintains
the characteristic number of chromosomes constant.
In this way, meiosis and
gametogenesis are always interlinked.
Question
11: Identify each part in a flowering plant and write whether it is haploid (n)
or diploid (2n):
(a)
Ovary (b) Anther (c) Egg (d) Pollen (e)
Male gamete (f) Zygote
Answer:
(a) Diploid (b) Diploid
(c) Haploid (d) Haploid (e) Haploid (f) Diploid
Question
12: Define external fertilisation. Mention its disadvantages.
Answer: External Fertilisation- When
fusion of gametes occurs outside the body of organisms (in the external medium
like water), the process is called "external fertilisation".
Its major disadvantages
are as follows:
1. A large nunnery of
gametes are required.
2. A large number of
offsprings are produced.
3. Chances of gametic
fusion are less.
4. The chances of
syngamy are less.
5. The offspring formed
are extremely vulnerable to predators, which threaten their survival upto
adulthood.
6. They are also exposed
to harsh environmental condition.
Question
13: Differentiate between a zoospore and a zygote.
Answer:
Zoospore
|
Zygote
|
Fig: Zoospores of Chlamydomonas
1. They are involved with asexual
reproduction.
2. Zoospores are formed in simple
plants, algae, or fungi.
3. They are microscopic motile
structures formed from parent body. No gametic fusion is involved.
|
Fig: Zygote
1. They are involved in sexual
reproduction.
2. Zygote is formed in complex
organisms.
3. This is formed because of fusion
of male and female gametes.
|
Question
14: Differentiate between gametogenesis from embryogenesis.
Answer:
Gametogenesis
|
Embryogenesis
|
1. Gametogenesis involves the
formation of haploid gametes in the gonads.
2. It leads to fertilisation.
3. It is of two types:
(a) spermatogenesis, and
(b) oogenesis.
4. It is variable in different
organisms.
|
1. Embryogenesis involves the
transformation of zygote into a multicellular organism.
2. It leads to birth.
3. It is a complex process which
involves:
(a) gametogenesis, (b)
fertilisation, (c) cleavage, (d) gastrulation, (e) organogenesis.
4. It includes a definite series of
phases which are fundamentally similar in all sexually reproducing organisms.
|
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Question
15: Describe the post-fertilisation changes in a flower.
Answer: Post-fertilisation changes in a
flower:
1. After fertilisation,
the sepals, petals and stamens of the flower wither and fall off.
2. The pistil remains
attached to the plant.
3. The zygote develops
into an embryo (embryogenesis) inside the ovule.
4. The ovule develops
into a seed.
5. The ovary transforms
into the fruit with a thick wall, called pericarp.
6. The seeds are dispersed
after maturity.
Question
16: What is a bisexual flower? Collect 5 bisexual flowers from your
neighbourhood and with the help of your teacher find out their common and
scientific names.
Answer: Flowers which contain both stamen
and pistil are called hermaphrodite or bisexual flowers e.g., sweet potato.
[For second answer, consult
your schoolteacher]
Question
18: Why are offsprings of oviparous
animals at a greater risk as compared to offspring of viviparous animals?
Answer: In oviparous animals, the
development of zygote takes place outside the body of the female parent i.e.
they lay fertilised egg in safe environment. These eggs are covered by hard
calcareous shells and hatch young ones after a period of incubation. Because of
lack of proper parental care and risk of predators, the offspring of oviparous
animals are at a greater risk for survival. On the other hand, in viviparous
animals, the zygote develops into a young one inside the body of the female
organism. After attaining a certain age of growth, the young ones are delivered
out of the body of female organism. Thus, due to proper embryonic care and
protection, the chances are survival of young ones is greater in viviparous
organisms.
To see
answers of Question 1 – 9 and Solutions of CBSE Hot Questions and Value Based Questions (VBQs) for Chapter 1,
Reproduction in Organisms, please click below:
- CBSE Class XII, Reproduction in Organisms - NCERT solutions of Biology textbook exercise questions (1 – 9)
- Reproduction In Organisms - VBQs for CBSE Class 12 Biology
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