Sexual reproduction involves the joining (fusion) of male and female…

The idea

Sexual reproduction requires the fusion of male and female gametes, which are specialised sex cells. In animals, the male gamete is the sperm cell and the female gamete is the egg cell. In flowering plants, the male gamete is contained within pollen and the female gamete is the egg cell found in the ovule. The fusion of gametes is called fertilisation and results in a zygote that develops into a new individual. Gametes are haploid, meaning they contain half the normal number of chromosomes, so that the offspring has the correct diploid number after fertilisation.

For example: In humans, a sperm cell fuses with an egg cell to form a zygote with 46 chromosomes.

What earns the marks

• Sexual reproduction involves the fusion of male and female gametes.
• In animals, the male gamete is the sperm cell and the female gamete is the egg cell.
• In flowering plants, the male gamete is in pollen and the female gamete is the egg cell.
• Fusion of gametes is called fertilisation.
• Gametes are haploid, so the offspring receives half its chromosomes from each parent.
• The fusion of gametes leads to the formation of a zygote.

Common mistakes and how to put them right

• Confusing the male gamete in plants.

  Put it right: The male gamete is inside pollen.

• Thinking gametes are diploid.

  Put it right: Gametes are haploid.

• Believing fertilisation occurs without fusion.

  Put it right: Fertilisation is the fusion of gametes.

Exam tips

• Name the specific gametes for animals and flowering plants.
• Use the term 'fusion' when describing fertilisation.
• State that gametes are haploid and the zygote is diploid.