PSYC 2000 Chapter : Research Methods In Psychology 9 2 14
Document Summary
Most recent hypothesis about animal phylogeny (figure 32. 11) Concept 33. 1: sponges are basal animals that lack true tissues. Filter water passing through their bodies (figure 33. 4)- pores: doughnut shaped cells that span body wall. Choanocytes: line the spongeocoel; movement of flagella sets up water flow. Choanocytes trap food and ingest it by phagocytosis; pass it along to amoebocytes. Amoebocytes: transport nutrients to other cells; secretes spicules. Concept 33. 2: cnidarians are an ancient phylum of eumetazoans (true tissue layers) A wide range of sessile (don"t move as adults) and floating forms including jellyfish, corals, and hydras. Simple diplablastic (2 tissue layers), radial body plan: body plan is a sac with central gastrovascular cavity. Single opening serves as both mouth and anus. Mesoglea layer (jelly of jellyfish) between epidermis and endodermis (gastrodermis) Medusa form moves freely in water by passive drifting and contractions of the bell.
