Phylum
A group of closely related classes in a kingdom is called a phylum. It is a taxonomic rank below kingdom and above class.
its called a phylum
swimming
The group of vertebrates most closely related to birds are probably the dinosaurs.
a Class
its phylum! (probably)
family
a population i think.
a bunch of hookers
which group are starfishes more closely related arthropods or jellfishes
About as closely as we are to frogs. Crustacea and Chelicerata (arachnids) are different classes in the same phylum (Arthropoda), just like mammals and amphibians are different classes in the phylum Chordata (vertebrates).
It depends how large the group is and how closely they are related.