Fertilisation

Fertilisation is the process in sexual reproduction where a male gamete and a female gamete join together. Gametes are special reproductive cells which themselves are sexually differentiated. The female gametes are called egg cells or ova whilst the male gametes are called sperm. When the cells join during fertilisation, the fertilized cell is called a zygote. This develops into an embryo and a new individual of the species. The fertilisation of a female gamete by a male can take place in one of two ways, depending on the species. In most land animals, fertilisation takes place internally (internal fertilisation), that is the sperm is passed from the male into the female’s body. However, in some animals, notably fish and amphibians, the female lays unfertilised eggs for the male to pour his sperm over. This process is called external fertilisation. Most animals with external fertilisation produce many eggs so that enough will survive (some will be lost or eaten) to be fertilised.