Members of a species are not all alike, partly because of differences in heredity (genetics). This is true even with children of the same parents. Some of these differences might make one organism better at surviving and reproducing than others in a particular habitat. When this organism reproduces, its children get the genes, which gave it the advantage. Some adaptations are extremely long-lasting, useful in many habitats. The evolution of wings in birds environment stays the same. If the environment changes enough, then another organism might do better.