BSC 196 Lecture 18: BSC 196- Lecture 18
Document Summary
They account for more than 95% of known animal species. Animals in the phylum porifera are known informally as sponges. They are sedentary and live in marine or fresh waters. Sponges are filter feeders, capturing food particles suspended in the water that passes through their body. Most sponges are hermaphrodites: each individual functions as both male and female. All animals except sponges and a few other groups belong to the clade eumetazoa, animals with true tissues: phylum cnidaria is one of the oldest groups in this clade. Cnidarians have diversified into a wide range of both sessile and motile forms including jellies, corals, and hydras. They exhibit a relatively simple diploblastic, radial body plan, but have a simple nerve net. The basic body plan is a sac with a central digestive compartment, the gastrovascular cavity: a single opening functions as mouth and anus. There are two variations on the body plan: the sessile polyp and motile medusa.
