Homologous structures are similar physical features in organisms that share a common ancestor, but the features serve completely different functions/18%3A_Evolution_and_the_Origin_of_Species/18.05%3A_Evidence_of_Evolution/18.5F%3A_Homologous_Structures). These structures are the result of divergent evolution, which is the process in which organisms from the same common ancestor evolve and accumulate differences, often resulting in a new species. Homologous structures do not have to look exactly the same or have the same function, but they are structurally similar. Examples of homologous structures include the limbs of humans, cats, whales, and bats, which are built upon the same bone structure. Another example is the eyes of humans and mice, which are homologous structures because we each inherited them from our common ancestor that also had the same sort of eyes.

In contrast, analogous structures are similar physical features in organisms that do not share a common ancestor. Instead, these structures are related to one another because they perform the same function. An example of analogous structures are the wings of a bat and the wings of a bird. They have completely different bone structure, but their wings share the same function, allowing the animal to take flight.

Homologous structures suggest that organisms have independently evolved similar traits, and they indicate a common ancestry and same developmental origin. Homologous structures are important in evolutionary biology because they provide evidence for common ancestry and help scientists to construct phylogenetic trees.