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29

$$ \text { In the figure given below, mark the ovule and pericarp. } $$

Explanation

In flowering plants, the zygote is formed inside the ovule. After fertilisation the sepals, petals and stamens of the flower wither and fall off. The pistil however, remains attached to the plant.

The zygote develops into the embryo and the ovules develop into the seed. The ovary develops into the fruit which develops a thick wall called pericarp that is protective in function.

30

Why do gametes produced in large numbers in organisms exhibit external fertilisation?

Explanation

Organisms that take part in such process produce large number of gametes because

(i) In external fertilisation, there is a great chance that the sperm and the eggs released by the organisms can be affected by factors present in the environment like dessication, predators, etc. So, to make up for the high fatality rate of the gametes, the organism produces a lot of gametes.

(ii) Producing large number of gametes increase the chance for at least some eggs and sperms to meet in the environment ensuring that atleast a stable number of offspring are able to survive and carry on.

31

Which of the following are monoecious and dioecious organisms?

(a) Earthworm ............... (b) Chara ...............

(c) Marchantia ............... (d) Cockroach ...............

Explanation

(a) Earthworm- Monoecious animal

(b) Chara-Monoecious plant

(c) Marchantia-Dioecious plant

(d) Cockroach- Dioecious animal

32

Match the organisms given in column I with the vegetative propagules given in column II.

Column I Column II
A. Bryophyllum 1. Offset
B. Agave 2. Eyes
C. Potato 3. Leaf buds
D. Water hyacinth 4. Bulbils
Explanation

$$ \text { The correct matching is as follows } $$

Column I
(Plant Angiosperms)
Column II
(Vegetative Propagules)
A. Bryophyllum 1. Leaf buds
B. Agave 2. Bulbils
C. Potato 3. Eyes
D. Water hyacinth 4. Offset

In plants, the units of vegetative propagation such as runner, rhizome, sucker, tuber, offset, bulb are all capable of giving rise to new offsprings. These structures are called vegetative propagules.

33

What do the following parts of a flower develop into after fertilisation?

(a) Ovary …….

(b) Ovules ……

Explanation

(a) Ovary .............. fruit

(b) Ovules ............ seed

After fertilisation, the zygote develops into the embryo and the ovules develop into the seed. The ovary develops into the fruit which develops a thick, protective wall called pericarp.