Natural Selection Step by Step: The Peppered Moth

0:00How does natural selection work? Let us follow some peppered moths, step by step.

0:06Peppered moths rest on tree bark during the day.

0:10Step one: the moths are not all the same. Most are light and speckled, but a few are dark.

0:18In places with lots of factory smoke, soot made the tree trunks dark.

0:24Step two: birds hunt the moths. On dark bark, the light moths are much easier to spot.

0:31The dark moths are better camouflaged, so more of them survive.

0:36Step three: the survivors have young, and the young inherit their colour from their parents.

0:43So the next generation has more dark moths than before.

0:48Step four: this happens again and again, in every generation.

0:54After many generations, most of the moths are dark.

0:59These four steps, working together, are called natural selection.

1:04So in natural selection, the living things best suited to their surroundings are more likely to survive, and pass their traits on to their young.