Heredity, Natural Selection, and Evolution

Species and Population

What are microevolution and macroevolution?

Microevolution is the change in allelic frequencies that occurs at the level of the population or species. When individuals with certain traits are more successful at reproduction, the ensuing generation will have more copies of that trait. Should the trend continue, eventually the traits will become so common in the population that the population profile will change. This is microevolution. Macroevolution is large-scale change that can generate entire new groups of related species, also known as a clade. One example would be the movement of plants onto land; all terrestrial plants are descended from that event, which occurred during the Devonian period about 400 million years ago.


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