Which of the following could be considered the most recent common ancestor of living tetrapods?

• A. Ray-finned fish
• B. Lobe-finned fish
• C. Jawless fish
• D. Cartilaginous fish

Answer: (B)

Verified step by step guidance

1. Understand the evolutionary tree of vertebrates: Vertebrates are a diverse group of animals that include fish, amphibians, reptiles, birds, and mammals. They evolved from a common ancestor and diversified into various lineages over millions of years.
2. Identify the key groups of fish: The major groups of fish include jawless fish, cartilaginous fish, ray-finned fish, and lobe-finned fish. Each group represents a different evolutionary branch.
3. Recognize the significance of lobe-finned fish: Lobe-finned fish are characterized by their fleshy, lobed, paired fins, which are joined to the body by a single bone. This group includes the coelacanths and lungfish, which are more closely related to tetrapods than other fish groups.
4. Connect lobe-finned fish to tetrapods: Tetrapods, which include amphibians, reptiles, birds, and mammals, are believed to have evolved from lobe-finned fish. The structure of their fins is similar to the limb bones of tetrapods, suggesting a common ancestry.
5. Conclude that lobe-finned fish are the most recent common ancestor of living tetrapods: Given the evolutionary relationship and anatomical similarities, lobe-finned fish are considered the most recent common ancestor of living tetrapods among the options provided.