Unit B

Module 4 ~ Lesson 3

 Evidence for Evolution


Anatomical structures that are similar because of common ancestry are homologous structures. For example, humans, frogs, bats, dolphins, and horses have the same basic arrangement of bones in their forelimbs. Homologous structures do not always share a common function.

Analogous structures are structures that are similar and have developed for the same function but do not share ancestry. For example, bird wings and insect wings are both adapted for flying but evolved independently of one another.

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The similarities in embryonic development among related groups, such as vertebrates, provides evidence for common ancestral origin.

Molecular Biology and Genetics

How similar organisms are on a molecular level can also provide evidence of common ancestry. For example, the proteins for many species can be observed at a cellular level. The similarities among all multi-cellular organisms suggest a common ancestor. Scientists can also compare patterns of DNA in various organisms. Species with similar patterns most likely inherited these from a common ancestor. Modern genetics supports Darwin's theory of inheritance, further supporting evolution by natural selection.

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