Fertilisation

In sexual reproduction, two germ-cells join. Each carries half the usual amount of DNA, so the zygote they form has the full amount again.

• In a flowering plant, the male germ-cell from the pollen grain fuses with the female gamete in the ovule. The zygote divides to form an embryo. The ovule becomes a seed, and the ovary becomes a fruit.
• In human beings, fertilisation happens in the oviduct, also called the fallopian tube. The zygote divides into a ball of cells, the embryo, which settles in the lining of the uterus.

A small example

Put the plant steps in order. Pollen lands on the stigma. A pollen tube grows through the style to the ovary. The germ-cells fuse in the ovule, and a zygote forms. The zygote becomes an embryo, inside a seed, inside a fruit. Pollination is the first step only.

Where marks go

Question 5 of CBSE's 2026-27 Science sample paper is about vasectomy and tubectomy. These surgical methods block the vas deferens in men and the oviduct in women. It asks what common event is prevented. The board's Science marking scheme for 2026-27 gives its 1 mark to the meeting and fusion of the male and female gametes.

Blocking the tubes does not stop gametes being made or hormones being released. It stops the two gametes from meeting. NCERT puts it plainly: "In both cases fertilisation will not take place." See where the marks go in CBSE Science.

About the author

Deepti Sardana

Founder Member & Academic Lead

An IIT alumna (M.Sc., M.Phil.) with over 25 years in teaching, child psychology and learning assessment. As Academic Lead at EduBrahma, she leads the method TRUtesting uses to find where and why a child loses marks.

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