Among the characteristics unique to animals is:

a. gastrulation

b. multicellularity

c. sexual reproduction

d. flagellated sperm

e. heterotrophic nutrition 2. what synapomorphy distinguishes animals as a monophyletic group, distinct form choanoflagellates?

a. multicellularity

b. coloniality

c. heterotrophy

d. no cell walls 3. based on morphological & molecular data, which living protist group is most closely related to animals?

a. poriferans

b. nucleariids

c. chytrids

d. choanoflagellates

e. dinoflagellates

First question:

a. Gastrulation

Gastrulation is a phase of the embryonic development in animals. It doesn't occur in plants or any other organism. The other options can be put apart because multicellularity, sexual reproduction, and flagellated sperm are also characteristics that are present in plants, for example. Heterotrophic nutrition is something that's part of all animals as well as non green plants.

Second question:

a. M ulticellularity

Synapomorphy is a shared trait that distinguishes a clade from other organisms. C hoanoflagellates are considered the most close ancestors to the animals distinguishing from them by multicellularity. They are very studied with the purpose to know the mechanisms of colonies' formation and evolution to multicellular animals.

Third question:

d. Choanoflagellates

This are the most closely related living protist group. The choanoflagellates are very similar to the ch oanocytes of the sponges bringing them into closeness with the animals. They even aggregate in colonies, and are thought, because of all of this, to be the closest branch of single cells to that of the animals.