Examine the evolutionary tree below. This tree tells us that the amnion is found in which of the following groups?

• A. All vertebrates
• B. Amphibians and fish
• C. Only mammals
• D. Reptiles, birds, and mammals

Answer: (D)

Verified step by step guidance

1. Examine the evolutionary tree provided in the problem. Evolutionary trees (phylogenetic trees) show relationships among organisms and the traits they share. Look for the placement of the amnion trait on the tree.
2. Understand the concept of the amnion. The amnion is a membrane that forms a protective sac around the embryo in amniotic eggs. This adaptation is found in amniotes, which include reptiles, birds, and mammals, but not amphibians or fish.
3. Identify the groups on the evolutionary tree that are labeled as having the amnion. These groups will be descendants of the branch where the amnion trait first appears.
4. Compare the groups listed in the question (all vertebrates, amphibians and fish, only mammals, reptiles, birds, and mammals) with the groups identified on the tree as having the amnion. Eliminate any groups that do not match the evolutionary placement of the amnion.
5. Conclude that the amnion is found in reptiles, birds, and mammals, based on the evolutionary tree and the biological significance of the amnion in these groups.