Some of the members of the protist kingdom have to take in food from their environment in order to survive as members of the animal kingdom. why are these organisms classified as protists and not as animals? they are unicellular and the members of the animal kingdom are all multicellular. they do not produce live young as the rest of the members of the animal kingdom do. they lack hair or fur and therefore cannot be classed as members of the animal kingdom. they are ectothermic while the members of the animal kingdom are all endothermic.