[2 Mark Question Answer]

Question 12 Marks

Given ahead is a diagrammatic representation of the process of fertilization. Study the same and then answer the question that follows:

What part does the stigma play in the process of fertilisation?

Answer

Role of Stigma:
During pollination, pollen grain is transferred to the stigma. Pollen grains are germinated only in the event of it falling on the stigma. Post germination, the pollen tube grows through the stigma, reaching the ovary in order for the egg cell to be fertilized.

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Question 22 Marks

Given ahead is a diagrammatic representation of the process of fertilization. Study the same and then answer the question that follows:

Name the parts labelled $1, 2, 3, 4, 5$ and $6$.

Answer

$1$→Style
$2$ → Pollen tube
$3$ → Polar nuclei
$4$ → Embryo sac
$5$ → Antipodal cells
$6$ → Micropyle

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Question 32 Marks

Given ahead is a diagrammatic sketch of the sectional view of a germinating pollen grain. Study the same and then answer the question that follows:

What happens to the part labelled $'5\ '$ during the process?

Answer

During germination of the pollen grain, part $ '5\ ' ($generative nucleus$)$ present at the tip of the pollen tube divides into two sperm nuclei. The pollen tube enters one of the synergids and releases its two sperm nuclei. Of these, one sperm nucleus enters the egg cell and fuses with its nucleus, while the other sperm nucleus moves towards the two polar nuclei in the central cell and fuses with them.

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Question 42 Marks

Mention any two contrivances in flowers which favour cross-pollination.

Answer

Contrivances in flowers whichfavourcross-pollination:

Unisexuality
Different timings of maturation of androecium and gynoecium
Self-sterility
Structural barriers

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BIOLOGY [2 Mark Question Answer]

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