Final Answer:
Homologous structures in different animals suggest a common evolutionary ancestry, indicating that these animals share a common ancestor. The presence of similar structures with variations in form and function implies divergence from a common ancestral structure due to adaptation to different environmental needs while retaining underlying similarities in anatomy.
Step-by-step explanation:
Homologous structures refer to anatomical features in different species that share a common evolutionary origin, despite possibly having different forms or functions. These structures suggest that organisms with these features are descended from a common ancestor who also possessed similar structures.
For instance, the forelimbs of vertebrates—such as the wings of birds, flippers of whales, arms of humans, and the forelegs of other mammals—display variations in function but have a similar underlying structure of bones. This similarity suggests that these structures originated from a common ancestor but have adapted over time to serve different purposes based on the needs of the species in their respective environments.
The existence of homologous structures supports the theory of evolution by demonstrating a shared ancestry among different species and the concept of descent with modification through the process of natural selection.