See the two kinds of variation, then run a peppered moth experiment and watch natural selection reshape a whole population.
Check yourself
What is the difference between continuous and discontinuous variation?
Continuous variation can take any value across a range, like height, and gives a smooth spread. Discontinuous variation falls into separate groups with no in-between, like blood group.
On dark, sooty bark, why do the dark moths survive better?
They are camouflaged against the dark bark, so birds are less likely to spot and eat them. More dark moths survive to breed, so the next generation has more dark moths.
Explain how this is an example of natural selection.
There is variation in colour. The environment favours the better camouflaged moths, which survive and reproduce more. They pass their colour on, so over many generations the population changes. This is evolution by natural selection.