Male and female gametes, and where fertilization happens
In higher plants and animals sexual reproduction uses two different kinds of gamete, male and female. Both are made by meiosis in the gonads. The male gametes can move. They have lost most of their cytoplasm, their body is pointed, and they have a tail, a flagellum, that moves them and carries the genetic material to the female gamete. Because some are lost on the way, four male gametes are made from each original cell. The female gametes are made in the ovary and usually stay in one place in the female’s body until fertilization. They are round and well supplied with food, and they are made in small numbers. Fertilization is the fusion of the nucleus of the male gamete with the nucleus of the female gamete. The zygote has the diploid number (2N) again and starts to divide by mitosis in the first steps of the embryo. Fertilization may take place outside the female’s body, which is external fertilization, as in bony fish and frogs. Or it may take place inside her body, which is internal fertilization, as in cartilaginous fish, reptiles, birds and mammals.
| Feature | Male gamete | Female gamete |
|---|---|---|
| Movement | moves, with a tail | stays in place in the female’s body |
| Shape | pointed body, little cytoplasm | round, with much food stored |
| Number | very many; 4 from each original cell | few |
| Made by | meiosis in the gonad | meiosis in the gonad |
| External fertilization | Internal fertilization |
|---|---|
| bony fish, frogs | cartilaginous fish, reptiles, birds, mammals |
Draw a comparison poster, with a grown-up. Fold a page in two. On the left draw a simple male gamete (a head and a tail) and list its features; on the right draw a simple female gamete (a large circle) and list its features. Along the bottom write the six animal groups of this lesson and tick whether each has external or internal fertilization. Stop at the biology of the gametes; no further detail is needed.