Cnidaria

The Evolution of Animals Eukaryotes come in two grades of organization: single-celled (protists) and multicellular (plants, animals, and fungi). The world today is full of complex multicellular plants and animals: how, why, and when did they evolve from protists? Proterozoic Protists A single-celled eukaryote or protist can carry chlorophyll (it can be an autotrophic, photosynthetic, "alga"), it can eat other organisms (it can be an organotrophic, "protozoan" "animal"), or it may do both