Heredity, Natural Selection, and Evolution

Species and Population

What are convergent and divergent evolution?

Scientists recently did a study of house dust mites and found that these members of the arachnids (related to spiders) demonstrated reverse evolution. Although Dollo’s law states that evolution is not reversible, genetic studies have shown that house dust mites—little mites that thrive in our mattresses, rugs, and sheets, or any place where we shed dead skin cells and are known as one of the most diverse animals on Earth—evolved from parasites. These parasites, in turn, evolved from free-living organisms millions of years ago. Now dust mites are back to their roots—literally—and are once again free-living organisms.

Convergent evolution occurs when diverse species develop similar adaptations in response to the same environmental pressure. For example, dolphins and sharks are descended from different ancestors, but as a result of sharing an aquatic environment, they have similar adaptations in body shape. When two species move away from the traits that they share with a common ancestor as they adapt to their own environments, the result is called divergent evolution. As an example, imagine the diversity among bird species. Ducks, hummingbirds, ostriches, and penguins are all descended from an ancestral bird species, yet they have all diverged as they adapted to their particular environments.


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