Page 55 - Science Coursebook

3.6 Natural selection

Comparing selective breeding and natural selection

The way in which the length of giraffes’ necks may have changed is called natural selection.
Natural selection is similar to the process of selective breeding. The table shows some ways in
which they are similar – but not quite the same.

Selective breeding Natural selection
To begin with, there is a population of organisms To begin with, there is a population of organisms that
that show variation. The variation is partly caused show variation. The variation is partly caused by their
by their genes. genes.
People choose individuals that have characteristics Individuals that have characteristics that provide the
that they want. best adaptations to their habitat are more likely to
survive.
Only the individuals with the characteristics that Only individuals with the best adaptations survive long
people want are allowed to breed. enough to breed.
These individuals pass on their genes, and there- These individuals pass on their genes, and therefore

fore their characteristics, to their offspring. their characteristics, to their offspring.
Question

2 Use the table to find two differences between selective breeding and natural selection.
Activity 3.6

Mountain hares and global warming

Mountain hares live in places that get very cold in
winter. Most mountain hares have coats that are
brown in summer and turn white in winter. This

camouflages them from foxes and other predators.
Some mountain hares have coats that do not turn
white in winter. They stay brown.
A mountain A mountain hare
In your group, use the theory of natural selection to hare in winter. in summer.
discuss what might happen to mountain hare coats if
global warming happens.
Make a presentation, or construct a poster, to
explain your ideas.

Summary
• Some of the variation between organisms is caused by their genes.
• Individuals that have variations that best adapt them to their
environment are most likely to survive and reproduce.

• These individuals pass on their genes to their offspring. The offspring

may inherit the genes for these adaptations.
• This process is named natural selection.

3 Variation and inheritance 53