
Concept explainers
Introduction:
Animals are classified as a monophyletic group, who share a common ancestor. The common animal ancestor was a multicellular organism as known from the data records, such as study of comparative morphology, fossils, comparative development, and comparative genomics.

Answer to Problem 1TYK
Correct answer:
The multicellularity is the derived trait that distinguishes animals as a monophyletic group and makes them distinct from choanoflagellates, since animals are multicellular and choanoflagellates are unicellular, free-living, colony-forming eukaryotes, and contain collared flagellates.
Explanation of Solution
Explanation/Justification for the correct answer:
Option (a) is given as multicellularity. Multicellularity represents the presence of more than one types of cells with different features and functions. Choanoflagellates differ from animals on the basis of multicellularity. Choanoflagellates do not exhibit muticellularity, whereas animals are multicellular organisms. Hence, option (a) is correct.
Explanation for incorrect answer:
Option (b) is given as coloniality. Coloniality refers association of organsims in form of colonies. It can be shown by both animals and choanoflagellates. So, it is an incorrect option.
Option (c) is given as heterotrophy. Heterotrphy shows state of being heterotropic that cannot produce their own food. Both animals and choanoflagellates are heterotrophs. So, it is an incorrect option.
Option (d) is given as movement. This characteristic is not classify animals from choanoflagellates, since both of the organisms are motile. So, it is an incorrect option.
Hence, options (b), (c), and (d) are incorrect.
Thus, it can be concluded the choanoflagellates are distinguished from animals on the basis of multicellarity.
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Chapter 33 Solutions
Biological Science
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