BIL 160 Lecture Notes - Lecture 11: Symmetry In Biology, Catenulida, Rhabditophora
28 Apr 2016
School
Department
Course
Professor
Document Summary
Sponges (porifera: no nervous system, radial symmetry, lack true tissues, filter feeders, choanocytes. Collar cells generate water current and ingest suspended food: mesohyl gelatinous layer between two cell layers. Cnidarians: sessile and motile forms, radial symmetry, a sac with central digestive compartment, polyp. Bell-shaped body with mouth on the underside. Anthozoans: sea anemones and corals, only polyps, corals form symbioses with algae and secrete hard exoskeleton. Each generation grows on remains of previous generation forming rocks. Bilaterians: bilateral symmetry and 3 germ layers and digestive tract with 2 openings. Flatworms: one opening, no true coelem (cavity for gas and fluid exchange, when have sex have to decide which one will be female (video in class) Flat shape maximizes area for this: catenulida. Chain worms can reproduce by budding: rhabditophora. Spend time in snails and then infect humans (2 hosts) Have to avoid 2 host immune systems. Look like plant with mosses but actually animals: brachiopods.
