In order for an animal to prevent its extinction, it needs to reproduce. Just as in the case of plants where there has to be male and female gametes, so it is in the case of animals. In fact, sexual reproduction in plants and animals are very similar. For the gametes (male and female sex cell) to be formed, meiosis has to occur.

The diagram above shows how meiosis occurs

It is important to note that the male gamete is always the one that moves toward the female gamete.

Also of importance is the fact that the female gamete is often larger than the male gamete.