Sexual Reproduction

Sexual reproduction involves two parents. The parents have sex organs which produce sex cells or gametes.  The male gamete is sperm and the female gamete is the egg.

Sexual reproduction is the fusion or fertilisation of the two male and female gametes to produce a fertilised egg or zygote

 

The fertilised egg goes on to divide many times to form a ball of cells.  This grows into an embryo which eventually develops into a separate individual.

 

Sex Cells (Gametes)

Sperm Cell
Sperm are highly specialised cells that contain that carry the genetic material of the male. A sperm cell has three main parts: the head, the body and the tail. In the head of the sperm is the nucleus which contains chromosomes ie the genetic information from the father. The tail of the sperm plays an important role as it beats and helps drive the sperm forward and swim towards the egg. 
 
Egg Cell
An egg cell is the female sex cell. In term of size it is much bigger than the sperm. It also has a nucleus which contains the female genetic information. A key difference from the sperm cell is that the egg has its’ own food store in the form of yolk contained in the cytoplasm. 

Fertilisation occurs when the nucleus of the sperm joins with the nucleus of the egg.

 



Comparison of the sex cells

Sperm cell Egg cell
Small Large
Mobile-swims using tail Cannot move as much
No food store Has own food store
Millions produced Much fewer produced