Ch 26- Sponges and Cnidarians What characteristics do all animals share? – Members of kingdom Animalia, multicellular, eukaryotic heterotrophs, lack cell walls Invertebrates- animals that do not have a backbone – 95% of all animal species – Range in size from dust mites to giant squids Vertebrates- animals that have a backbone – Fish, amphibians, reptiles, birds, mammals

What essential functions do animals carry out? – Feeding, respiration, circulation, response, movement, and reproduction What are the important trends in animal evolution? – High levels of cell specialization and internal body organization in complex animals – Bilateral body symmetry – Front end or head with sense organs – Body cavity

Sponges Why are sponges classified as animals? – Multicellular, heterotrophic, no cell walls, contain a few specialized cells Phylum Porifera Are sessile and filter feeders Body plan – Asymmetrical, forms wall around large central cavity – Choanocytes- specialized cells that use flagella to move steady current of water through sponge – Osculum- large hole at top of sponge – Spicule- spike shaped structrure made of chalklike calcium carbonate – Archaeocytes- specialized cells that move around within the walls of sponge

How do sponges carry out essential functions? – Movement of water throughout sponge Characteristics of sponges No true tissues or organs – Food digested by collar cells and nutrients are passed to rest of body – Produce toxins – Feed on bacteria, protozoans, unicellular algae – May reproduce either sexually or asexually Internal fertilization Gemmules- groups of archaeocytes surrounded by tough layer of spicules Play an important role in the primary productivity of coral reefs

Cnidarians What is a cnidarian? – Soft-bodied, carnivorous animals with stinging tentacles arranged in circles around their mouths – Simplest animals to have body symmetry and specialized tissues Cnidocyte- stinging cells, located along tentacles Nematocyst- poison-filled, stinging structure that contains tightly coiled dart

Form and Function in Cnidarians Polyp-sessile and vase shaped-cylindrical Medusa-swimming and bell shaped Radially symmetrical Most cnidarians reproduce both sexually and asexually

Groups of Cnidarians Jellfishes, hydras, sea anemones, corals Scyphozoa-means cup animals – Sexual reproduction – Medusa dominant form of life cycle – Nematocysts-poison – Common jellyfish Hydrozoa – Hydras are most common freshwater, lack a medusa stage – Sexual or asexually – Portuguese man-of-war Anthozoa – Sea anemones Sessile, only polyps Coastal areas Tentacles and feed on fish – Corals Polyps in colonies Calcium carbonate Warm clear water Coral reefs