Fertilisation

Fertilisation involves fusion of the sperm cell with the egg cell or ovum

Fertilisation takes place in the woman’s fallopian tubes

Sperm can stay in the fallopian tubes for up to 2 days

In some animals like fish, fertilisation is carried out externally meaning large numbers of eggs are produced so some will survive

After fertilisation, the fertilised egg begins to divide, making a ball of cells that become the foetus

Egg cells (ova) are quite large and have a food reserve.

Eggs cells are released from the ovary approximately once a month

Sperm cells are much smaller than ova and have a tail to help propel them forward.

Sperm cells are streamlined as they have a cytoplasm in the cell.

Sperm cells have a strengthened head which contains chemicals to penetrate and break down the outer layers of the egg

The egg cell and sperm cell each have half of the inherited information in their nuclei needed to male the fertilised egg cell

Identical twins come from one fertilised cell that split into two identical halves. All the nuclei in their cells is the same