Chapter 30, Problem 1TYK

What synapomorphy (shared, derived trait) distinguishes animals as a monophyletic group, distinct from choanoflagellates?

a. multicellularity

b. coloniality

c. heterotrophy

d. movement

Summary Introduction

Introduction:

Animals are classified as a monophyletic group (share a common ancestor). The ancestor was multicellular as known from the data records from 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. Choanoflagellates are unicellular, free-living, colony-forming eukaryotes, and contain collared flagellates. They are considered to be the closest living relatives of the animals.

Explanation of Solution

Explanation/Justification for the correct answer:

Option (a) is given as multicellularity. 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. The organisms exhibit the colonial characteristics, such as protozoa, bacteria, echinoderms, bivalves, and many more. Choanoflagellates are unicellular and are sometimes colonial (due to the presence of bacteria). So, it is an incorrect option.

Option (c) is given as heterotrophy. All the animals are heterotrophs along with fungi. Both the categories are motile. So, it is an incorrect option.

Option (d) is given as movement. This characteristic is not the basis of diversion of animals from choanoflagellates. So, it is an incorrect option.

Hence, options (b), (c), and (d) are incorrect.

Conclusion

The choanoflagellates are the closest relatives of animals, but they are distinguished from animals on the basis of multicellular organization.