BIOL 1002 Lecture Notes - Lecture 9: Gastrovascular Cavity, Gastrodermis, Body Plan
16 Aug 2019
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An overview of animal diversity-kingdom animalia part b: Invertebrates account for 95% of the known animal species and occupy almost every habitat. Sponges are basal animals that lack true tissues. Phylum porifera (sponges) are among the simplest of animals: sedentary, live in marine or fresh water, lack true tissues and organs. All animals except sponges and a few others belong to the clade eumetazoa, animals with true tissues. Phylum cnidaria is one of the oldest groups in the clade; includes corals, sea anemones, jellies, and hydras. Two variations on body plan: sessile polyp and motile medusa: polyp: adheres to substrate by aboral end of body (hydras, medusa: bell-shaped body with mouth on underside, do not attach to substrates but move freely (jellies) Some exist only as polyps or only as medusas, others have polyp and medusa stages in life cycle.
