when is an organism classified as a protist
Protist A protist (/ˈproʊtɪst/) is any eukaryotic organism that has cells with nuclei and is not an animal, plant or fungus. The protists do not form a natural group, or clade, since they have no common characteristic origin, but, like algae or invertebrates, they are often grouped together for convenience. In some systems of biological classification, such as the popular five-kingdom scheme proposed by Robert Whittaker in 1969, the protists make up a kingdom called Protista, composed of "organisms which are unicellular or unicellular-colonial and which form no tissues".[2][3][A]
Starfish The scientific name Asteroidea was given to starfish by the French zoologist de Blainville in 1830.[3] It is derived from the Greek aster, ἀστήρ (a star) and the Greek eidos, εἶδος (form, likeness, appearance).[4] The class Asteroidea belongs to the phylum Echinodermata. As well as the starfish, the echinoderms include sea urchins, sand dollars, brittle and basket stars, sea cucumbers and crinoids. The larvae of echinoderms have bilateral symmetry, but during metamorphosis this is replaced with radial symmetry, typically pentameric.[5] Adult echinoderms are characterized by having a water vascular system with external tube feet and a calcareous endoskeleton consisting of ossicles connected by a mesh of collagen fibres.[6] Starfish are included in the subphylum Asterozoa, the characteristics of which include a flattened, star-shaped body as adults consisting of a central disc and multiple radiating arms. The subphylum includes the two classes of Asteroidea, the starfish, and Ophiuroidea, the brittle stars and basket stars. Asteroids have broad-based arms with skeletal support provided by calcareous plates in the body wall[7] while ophiuroids have clearly demarcated slender arms strengthened by paired fused ossicles forming jointed "vertebrae".[8]