Key ideas1 of 3
Start with variation
Individuals in a population vary. Some differences are inherited because individuals have different versions of genes. Random mutations can create new genetic variants. A mutation does not happen because an organism needs it.
In this model, light and dark insects are present before selection occurs. On a dark surface, predators may spot light insects more easily. This creates a difference in the insects' chances of surviving. All living species evolved from simple life forms that first developed more than three billion years ago.
