Invertebrate Animals What you need to know

Sponges Characteristics – simplest animals, no tissues, Examples – Venus flower basket, bath sponge Support – spicules – calcium, silica or protein Movement – sessile (don’t move) Food Getting – collar cells capture food Digestion – by vacuoles Circulation – collar cell flagella move water through, amoeba like cells move food vacuoles around Respiration – no Nervous – no Reproduction – budding and sexual Importance/Nature – clean/filter huge amounts of water Importance/Economy – minor, bath sponge formerly very important

Cnidarians Characteristics – true tissues, 2 tissue layers, tentacles, stinging cells, radial symmetry Examples – coral, anemone, jellyfish, hydra, Portuguese man-of-war Support – water pressure Movement – muscle cells and a ring of muscle around the bell of the medusa form Food Getting – stinging cells, tentacles Digestion – one cavity Circulation – no system Respiration – no system Nervous – a nerve ring in the mesoglea (middle layer) Reproduction – budding & sexual. Some alternate generations Importance/Nature – big link in food chain, feed on plankton, corals provide home for most of the ocean’s species Importance/Economy – coral, anemone Vocabulary - medusa, polyp, mesoglea

Flatworms Characteristics – 3 tissue layers, distinct head, many parasitic Examples – planarians, flukes, tapeworms Support – still just water pressure Movement – cilia & simple muscles Food Getting – pharynx Digestion – still only one opening parasites absorb food directly Circulation – some, minor Respiration – mostly diffusion Nervous – nerve ladder, ganglia at head end Reproduction – many are hermaphrodites Importance/Nature – scavengers and parasites Importance/Economy – flukes and tapeworms are serious infections

Roundworms Characteristics – 3 tissue layers, simple tube-within-a-tube body plan. all are small hugely abundant, many are parasites Examples – nematodes, rotifers, tardigrades Support – H2O pressure, cuticle Movement – longitudinal muscles allow for simple undulations Food Getting – most are scavengers or parasites Digestion – complete(mouth & anus) pharynx Circulation – some Respiration – still diffusion Nervous – nerve ring Reproduction – most have separate sexes Importance/Nature – major decomposer and component of soil Importance/Economy – parasites including hookworm

Segmented worms Characteristics – tube-within-a-tube plan. segmented body, much more complex than other worms Examples – earthworms, marine worms, leeches Support – muscles Movement – both circular and longitudinal muscles control each segment Food Getting – scavengers Digestion – complete system including a crop Circulation – closed system with simple “hearts” Respiration – some with gills, others use diffusion Nervous – nerve cord and ganglia Reproduction – most hermaphroditic Importance/Nature – supreme recyclers of soil Importance/Economy – fish bait, medical leeches

Mollusks Characteristics – Soft body, shell producing mantle, radula. 2nd largest group of animals Examples – clam, snail, squid, octopus Support – shell Movement – foot or jet propulsion Food Getting – scav, filter feeders and carnivores Digestion – complete Circulation – open system with heart and sinuses Respiration – gills Nervous – smartest invertebrates Reproduction – separate sexes except the snail, usually external fert. Importance/Nature – fill many niches Importance/Economy – major food source

Echinoderms Characteristics – water vascular system, spiny skin, radial symmetry, all bottom dwellers, Examples – starfish, sea cucumber, sea urchin Support – spiny skin Movement – water vascular system, tube feet Food Getting – herbivores or carnivores, Digestion – some can invert stomach, mouth on bottom, anus on top Circulation – water vascular system Respiration – water vascular system or gills Nervous – decentralized, no “brain” Reproduction – external, also can regenerate Importance/Nature – scav, some carnivores, some eat corals Importance/Economy – urchins in development. Some are pests