A snake does not have legs. Nevertheless, it has tiny hip-like bones in its midsection where legs could reasonably attach. The bones have no function. How do the hip bones of a snake provide evidence for the evolution of snakes? A. The hip bones are vestigial structures that show evolutionary descent from an ancestor that had legs. B. The hip bones are analogous structures with the leg bones of other animals, and show how they all evolved from a common ancestor. C. The hip bones are vestigial structures that show that snakes, worms and other legless animals evolved by adaptive radiation. D. The hip bones are homologous structures with the vertebrae and other bones of the snake, and show the sequence in which the vertebrate skeleton evolved.

## Step 1<br />The problem is asking us to identify the correct explanation for the presence of hip bones in snakes, which are legless. The hip bones in snakes are remnants of an ancestor that had legs. These remnants are known as vestigial structures.<br /><br />## Step 2<br />Vestigial structures are parts of an organism that are reduced from their original ancestral form and are usually nonfunctional. They provide evidence for evolution because they show the remnants of features that were once functional in ancestral species but are no longer needed in the current species.<br /><br />## Step 3<br />The hip bones in snakes are vestigial structures because they are remnants of an ancestor that had legs. They are not analogous structures, which are structures in different species that have the same function but have evolved separately, nor are they homologous structures, which are structures in different species that have evolved from a common ancestor.<br /><br />## Step 4<br />The hip bones in snakes are not evidence of adaptive radiation, which is a process in which species diversify rapidly from an ancestral species into a variety of forms to fill different ecological niches.