Question

1. It is thought that the animal evolutionary lineage descended from choanoflagellates (or a choanoflagellate-like common ancestor). Why are some researchers interested in comparing choanoflagellates to choanocytes of sponges?

2. Cnidarians lack a centralized nervous system, but they do have a ____________that responds to stimuli by activating muscle tissue. (1)

3.Members of the Phylum Cnidaria are the only organisms to have ____________________________, structures used to inject venom into prey (also helpful for defense).

Answer 1

Answer 1. Scientists wants to compare because of the similarities between the choanoflagellates and the choanocytes. Both have similar morphology with respect to the presence of collar cell and flagella. Both help in the movement of water that helps in drawing food.

Besides this, there are differences too like sponges that bear choanocytes are multicellular, and asymmetrical too.

Overall, the similarities are more than dissimilarities that accounts for that both choanoflagellates and choanocytes have originated from a common ancestor.

Answer 2. Nerve net.

Answer 3. Nematocysts.