Final-Answer:
Anatomical similarities and differences between various organisms (living today or fossils) help infer lines of evolutionary descent by providing evidence of shared ancestry. For example, the presence of a backbone in humans, fish, and birds is evidence that these organisms share a common ancestor. Similarly, the presence of feathers in birds and dinosaurs is evidence that these organisms are closely related.
Anatomical similarities can be either homologous or analogous. Homologous structures are similar because they share a common evolutionary origin, while analogous structures are similar because they have evolved to perform similar functions in different organisms. For example, the wings of birds and bats are homologous structures, as they both evolved from the forelimbs of a common ancestor. The wings of birds and insects, on the other hand, are analogous structures, as they both evolved to perform the function of flight, but they have different evolutionary origins.
Anatomical differences can also provide evidence of evolutionary descent. For example, the presence of fur in mammals and hair in humans is evidence that these organisms are closely related, but the fact that mammals have fur and humans have hair is evidence that these organisms have diverged from a common ancestor.
By comparing the anatomical similarities and differences between various organisms, scientists can infer the lines of evolutionary descent. This information can be used to understand the history of life on Earth and to predict how organisms may evolve in the future.
