(i) Explain with the help of a diagram how pollen after landing on the stigma of a flower helps male germ cell to reach the female germ cell. Label the following: ovary, female germ cell, male germ cell and pollen grain. (ii) State the meaning of pollination and mention a distinguishing feature between self-pollination and cross-pollination. OR State in brief the changes that take place in a fertilized egg (zygote) till birth of the child in the human female reproductive system. What happens to the egg when it is not fertilized?

Part (i)

Process of Fertilisation in Flowering Plants:

1. Germination: After a pollen grain lands on a compatible and suitable stigma, it absorbs moisture and germinates.
2. Pollen Tube Growth: A pollen tube grows out of the pollen grain and travels downwards through the style to reach the ovary.
3. Travel of Male Gametes: The male germ-cells (gametes) travel through this pollen tube.
4. Fertilisation: The pollen tube enters the ovule inside the ovary. The male germ-cell fuses with the female germ-cell (egg cell) present in the ovule. This fusion is called fertilisation, which results in the formation of a zygote capable of growing into a new plant.

Part (ii)

• Pollination: The transfer of pollen grains from the stamen (male reproductive part) to the stigma (female reproductive part) of a flower is known as pollination.
• Distinguishing Feature:
• Self-pollination: The transfer of pollen occurs within the same flower or between flowers of the same plant.
• Cross-pollination: The transfer of pollen occurs from the flower of one plant to the flower of another plant of the same species, which is typically carried out by external agents like wind, water, or animals.

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OR Option

Changes in a fertilized egg (zygote) till birth:

1. Division and Implantation: The zygote divides several times to form an embryo. This embryo is implanted in the thick, spongy inner lining of the uterus.
2. Nourishment via Placenta: The embryo gets nutrition from the mother's blood through a specialized disc-like tissue embedded in the uterine wall called the placenta. It provides a large surface area for glucose and oxygen to pass from the mother to the embryo, and also helps in removing metabolic wastes.
3. Gestation: The embryo grows and develops organs sequentially. The period from fertilisation to birth (gestation period) is about 9 months in humans.
4. Birth: The child is born as a result of rhythmic contractions of the muscles in the uterus.

What happens when the egg is not fertilized:

1. If the egg is not fertilized, it survives for about one day.
2. The thick, spongy lining of the uterus, which was prepared to receive the zygote, is no longer required.
3. This lining slowly breaks down and is discharged along with blood and mucous through the vagina.
4. This monthly cycle of discharge is called menstruation, which lasts for about 2 to 8 days.