BSC 2011C Chapter Notes - Chapter 1: Cnidaria, Endoderm, Flatworm
Document Summary
Phylum porifera sponges multicellular, eukaryotic organisms that diverged from protists: don"t move sit and filter water for food, embyos don"t have any layers, only cells. Cnidaria jellies, sea anemones, corals, and hydras: develop 2 germ layers endoderm and ectoderm (diplastic) Form a tube that allows an animal to ingest, digest, and get rid of stuff: only one hole that serves as mouth and anus and they don"t have organs, ectoderm contains stinging cells called cnidocytes. Platyhelminthes soft, unsegmented worms, includes flatworms, planaria, tapeworms: triploblastic (3 germs layers) endo- ecto- and mesoderm. Ectoderm forms brain, nervous system and skin. Mesoderm forms muscles, bones, cartilage and heart and blood. Endoderm forms digestive and respiratory systems: mesoderms key feature coelom. Fluid filled cavity that stores and protects major organs. Allows internal organs to move independent of body wall. Fluid provides shock resistance: acoelomates don"t have a coelom, but are triploblastic. Nematoda unsegmented roundworms: pseudocoelomates incomplete body cavity, a lot live in humans.
