Which of the following is the most likely ancestor from which animals evolved?

• A. Green algae
• B. Cyanobacteria
• C. Slime molds
• D. Choanoflagellates

Answer: (D)

Verified step by step guidance

1. Understand the question: The problem is asking about the most likely ancestor of animals. This requires knowledge of evolutionary biology and the characteristics of different organisms.
2. Review the options: Green algae, cyanobacteria, slime molds, and choanoflagellates. Each of these groups has distinct evolutionary traits and relationships to animals.
3. Eliminate unrelated groups: Green algae are more closely related to plants, cyanobacteria are prokaryotic and not directly related to animals, and slime molds are part of the Amoebozoa group, which is not closely related to animals.
4. Focus on choanoflagellates: These are single-celled or colonial eukaryotes that share a striking resemblance to the collar cells (choanocytes) of sponges, one of the simplest animal groups. This similarity suggests a close evolutionary relationship.
5. Conclude that choanoflagellates are the most likely ancestor of animals based on molecular and morphological evidence, as they share a common ancestor with the earliest animals.