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Cnidarians Characteristics • Cnidarian means Thistle • Referring to the stinging cells (nematocysts) that all members possess • All aquatic • Radial symmetry • Body has a single opening through which food and wastes pass • Has a gastrovascular cavity where digestion begins Symmetry Gastrovascular cavity Nematocysts • Some can move around, others are sessile • Two tissue layers, the ectoderm(outer) and the endoderm ( inside) • Simple nervous system and muscle tissue • Reproduce asexually by budding and sexually by producing gametes. Cnidarians are hermaphrodites Hydra, Jellyfish, Sea anemones, Coral • • • • • • • • • Platyhelminthes Means flat and wide Simplest animals with bilateral symmetry Have organs and organ systems Have an anterior end and so move in a forward direction 3 tissue layers: endoderm, mesoderm and ectoderm Lack a body cavity Some have a primitive brain and sensory organs Planarians are free-living, while tape worms and flukes are parasites Reproduce sexually and asexually Planaria, tape worms and flukes Nematode Worms • • • • • • • • Means thread-like Commonly called roundworm Some are free-living and some parasitic Distinct head and organ systems Tube within a tube body plan Has a pseudo coelom (body cavity) Sexual reproduction Some species are hermaphrodites Annelids • Annelida means ring • Referring to the body being segmented into repeating units • The only group of segmented worms • They live on land and in water • They have complete digestion, a closed circulatory system, a ventral nerve cord, a nephridial excretory system, and a true body cavity • Digestion is extracellular ( in special compartment in the body, not in cells) • Sexual reproduction, internal fertilization, some are hermaphrodites True body cavity Earthworms, clamworms, leeches Gross!!!! • In 1994, a woman's scalp was ripped off when her hair was yanked into moving machinery. Doctors performing micro-surgery at the University of Southern California reattached the scalp, but one area swelled with congested blood. They applied leeches, one at a time for eight days, to suck up stagnant blood. Eventually new capillaries, or tiny blood vessels, formed in the scalp wound, leading to healing circulation. Mollusca • • • • • • • Means soft-bodied unsegmented Most live in water, a few (slugs) live on land Most have an internal or external shell Have a mantle (fold in the body wall that lines the shell) Muscular foot and/or tentacles All except bivlaves have a radula and a well-developed head • Most have an open circulatory system, some have closed circulation • Many respire using gills, slugs use a hole in the side of their head and breath through their skin • Gums to bums digestion Arthropods • • • • • • • • • The most successful phylum (106 to 107 species) Means “jointed foot” but have jointed appendages Very diverse group Reproduce sexually, most have separate sexes Rigid, jointed exoskeleton provides a waterproof protective armor, a site for muscle attachment, protection from drying Well developed nervous system Most have an open circulatory system, breath using gills, trachea, book lungs Well developed excretory system ( kidneys) One way digestive system Echinoderms • • • • • • • • Means spiny skinned Most advanced group of invertebrates Radial symmetry Digestion is extracellular, one way digestive system Reproduction is sexual, asexual powers of regeneration Does not have a centralized nervous system Has an endoskeleton made of calcium carbonate plates Water -vascular system with “tube feet”helps catch food, with movement and gas exchange