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Sponges, Cnidarians, Flatworms, Roundworms

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Phylum Porifera, sponges;
   -their symmetry is asymmetrical
   -most are marine
   -are filter feeders
   -have no true tissues
   -structure includes osculum, pore cells, epithelial cells, collar cells, amoebocytes, and spicules
   -budding, group of cells that are released and start new organism
   -infernal fertilization
   -external fertilization, eggs and sperm are released outside of organism

Phylum Cnidaria, invertabrates;
   -their symmetry is radial
   -have tissues but no organs
   -have two life stages, first a polyp attached to the floor, then a medusa free to move around
   -their digestion invovles nematocysts, gasrtovascular cavity, and an opening that is an enrantce and an exit to the GVC
   -diffusion is enough to get oxygen and get rid of carbon dioxide
   -have a nervous system with simple nerves arranged into a net
   -have no brain
   -reproduce sexually during the medusa stage and asexually during the polyp stage
   -Portugese Man of war
   -Jellyfish, Class Seyphozoa
   -Sea anemones, Class Anthozoa
   -Corals, Class Anthozoa

Phylum Platyhelminthes, flatworms;
   -three major divisions: cystota and trematota are parasitic, turbolaria is free living
   -have bilateral symmetry
   -have tissues and organs but are acoelemate
   -free living eat dead matter
   -nervous system has a ganglia, two nerve cords and eyespots which detect light
   -rely on diffusion
   -have a highly branched GVC
   -reproduction is hermaphroditic
 Tapeworms are modified to be parasites. They have a sculex (head), hooks and suckers.
 Flukes are parasitic and have a tendency to invade the liver and blood vessels

Phylum Nematoda, roundworms;
   -is a large phylum but most of the species are unidentified
   -have tissues, organs and organ systems
   -are psuedocoelomate
   -are mostly parasitic
   -have a hydrostatic skeleton
   -muscles only run lengthwise
   -include hookworms, pinworms and heartworms
   -can cause trichinosis and elephentosis