[Campbell Biology P.725] According to Figure 32.4 and the accompanying text, which statement... | Practice Question

According to Figure 32.4 and the accompanying text, which statement best describes the significance of the "CCD" domain in the context of animal evolution?

  • A: The "CCD" domain is essential for choanoflagellate cell attachment, indicating their close relationship to animals.
  • B: The "CCD" domain is found in both choanoflagellates and animals, suggesting a common ancestor for all eukaryotes.
  • C: The "CCD" domain is unique to animals and its incorporation into ancestral choanoflagellate protein domains likely contributed to the evolution of animal multicellularity.
  • D: The "CCD" domain's absence in choanoflagellates indicates that these organisms are not related to animals.

Explanation

Figure 32.4 and the text explain that the 'CCD' domain is unique to animals and is not found in choanoflagellates. The text further suggests that the cadherin attachment protein in animals originated from a rearrangement of existing choanoflagellate protein domains combined with the incorporation of this novel 'CCD' domain, which was a key step in the transition to multicellularity.