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Invertebrates Invertebrates • • • • Major Phyla Porifera = Sponges Cnidarians = Jellyfish Mollusks = Squids, clams, snails • Annelids = Earthworms, leeches • Arthropods = insects, crustaceans Phylum Porifera • AKA: Sponges • Most primitive animals (>570myo) – Related to subgroup of animal-like protista • ~9000 species (most saltwater) • Sessile (stationary) • Reproduction: – Sexual: egg and sperm released into water • Larva attaches to surface and grows into sessile adult – Asexual: Budding Sponge Structure • Filter feeders: – Water sucked in through many pores – Water exits through osculum • Bodies made of 2 cell layers – No body symmetry – Pinacocytes (Outer layer): Flat, protective cells – Collar Cells (Inner layer): cells with cilia to create current • Specialized Cells – No tissue, organs, or systems – Amoebocytes: digest and transport nutrients around the body Phylum Cnidaria • Basic Characteristics • Radial symmetry • Two body forms: – 1) Polyps: tubes with mouth and tentacles facing upward – 2) Medusa: Umbrella-shaped with mouth and tentacles downward Phylum Cnidaria • Reproduction – Asexual: Budding – Sexual: Sperm and egg released into water; new polyp created • Anatomy – 2 tissue layers (evolutionary advancement) • 1) Ectoderm (outer layer): covered with stinging cells • 2) Endoderm (inner layer) • Gastrovascular cavity: single opening to digest food
