Page 54 - Science Coursebook

3.6 Natural selection

We have seen how selective breeding can, over time, produce new varieties of animals
and plants. Can a similar process happen in the wild, without any involvement of
humans?

Let’s think about how this might work. We will use an imaginary example.

Long ago, in a population of giraffes, some had long necks and some had short necks.

This was because they had different forms of a gene. The giraffes ate leaves on trees.

One year, there was a severe drought. Food was in short supply. When all the lower

leaves had been eaten, only the long-necked giraffes could get food.

Most of the short-necked giraffes died. Only the long-necked giraffes survived.

The long-necked giraffes reproduced. Their offspring inherited the genes for long necks.

Question
1 From the giraffe story, give an example of each of the following:

a variation
b adaptation

c a factor affecting the size of a population.

52 3 Variation and inheritance

A+I A+E SE