Concept 8 Sex cells have one set of chromosomes; body cells have two.

Gametes are usually smaller than the organisms that make them. However, at 2 mm, fruit fly sperm is as long as the fly itself and 300 times longer than human sperm. Another species of fly, Drosophila bifurca, makes sperm that are 6 cm long, 20 times larger than the flies.

Only one sperm is needed to fertilize one egg, however, the sperm to egg ratio is usually thousands or even millions to one. Why do you think this is the case?