Eli5: Animalia phylum. Why are there so many divisions for worms while mammals, fish, amphibians, birds, and reptiles all get lumped into Chordata?

Question

Flatworms (Platyhelminthes), Roundworms (Nematoda), Segmented worms (Annelida), acorn worms (Hemichordata) all get their own phylums. Why?

In: Biology

Answer 1

I believe a lot has to do with how the worms develop in the embryonic stages, these differ a lot compared to how chordata develop. As chordata usually rely on a similar developing patterns early on in the embryonic stages (f.e. at certain stages we would resemble an amphibian embryo).

Whilst worms, i think, have a lot of different ways of organizing within an embryo. Not sure about the differences exactly but i do know i studied this for a semester lol. Different ways of cell structures migrating and developing within the embryo.

Hope this helps a bit 😀

Beinj