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Chapter 33: An Introduction to Invertebrates33.1: Sponges-General characteristics•In the animal phyla, Porifera•Suspension feeders: capture food particles suspended in the water that passes through their body•Water flow goes through the poresspongocoelout of osculumoInside of spongocoel lie flagellated choanocytes, which engulf bacteria and other food particles by phagocytosis•More complex sponges have folded body walls•Lack true tissues•The body of a sponge consists of two layers of separated by a gelatinous region called the mesohyloGas exchange and waste removal can occur via diffusionoOther tasks are performed by cells called amoebocytes•Most sponges are hermaphrodites(both male and female parts)oEggs reside in mesohyl, fertilization occurs in mesohyl33.2: Cnidarians-General characteristics•Where the eumetazoa clade begins on the animal phylogeny•Cnidarians include hydras, corals, and jellies•Body planoDiploblastic and radialoContains a sac with a central digestive compartment called the gastrovascular cavityoTwo variationsSessile polyp•Polypsare cylindrical forms that adhere to the substrate by the aboral end of their bodyMotile medusa•Medusaresembles a flattened, mouth-down version of the polyp•Carnivores that use tentacles arranged in a ring around their mouth to capture prey and push the food into their gastrovascular cavityoThe tentacles are armed with batteries of cnidocytes, cells unique to cnidarians that function in defense and prey capture•Phylum is divided into four major clades: Hydrozoa, Scyphozoa, Cubozoa, and Anthozoa-Hydrozoans•Alternate between the polyp and medusa form•Under ideal conditions, asexually reproduce by budding•Under not ideal conditions, sexually reproduce
-Scyphozoans•True jellyfish class-Cubozoans•Box-shaped medusa stage•Strong swimmers•Ex. Sea wasp-Anthozoa•Corals•Occur only as polyps•Form symbioses with algae33.3: Lophotrochozoans-General characteristics•Where bilateria clade begins on animal phylogenyoMost bilaterians have a digestive tract with two openings (mouth and an anus) and a coelemo