Evolution and inheritance
Biology · Key Stage 2 · The School
The evidence in the rock
Fossils are the remains or traces of living things preserved in rock, and they show that the living things on Earth have not always been the ones here now. Some fossil animals have no living match at all. Others are recognisably related to animals alive today but not identical to them. Fossils are dated by the rock layers they sit in — deeper is generally older.
Like your parents, but not identical
Living things produce offspring OF THE SAME KIND: dogs have puppies, oaks make acorns that grow into oaks. But offspring are not copies. Puppies in one litter differ in size, coat and temperament. Some of that variation is inherited from the parents and some comes from the environment, and it is the inherited part that matters for what follows.
How a population changes
Animals and plants are ADAPTED to where they live — thick fur in the cold, deep roots in dry ground, a beak shaped for the food available. Because offspring vary, some individuals happen to be better suited than others. Those individuals are more likely to survive and have young, and they pass that variation on. Over many generations the whole population shifts. That is EVOLUTION.
A population of beetles is half green and half brown, on brown soil. Birds spot the green ones more easily and eat more of them. The survivors are mostly brown, so more brown beetles breed, and the next generation is mostly brown. No individual beetle changed colour. What changed was the PROPORTION in the population — which is exactly what evolution by natural selection means.