Chapter 33 Study Guide - Chapter 33 An Introduction to Invertebrates 33.1 Sponges-General characteristics In the animal phyla Porifera Suspension

Chapter 33 Study Guide - Chapter 33 An Introduction to...

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Chapter 33: An Introduction to Invertebrates 33.1: 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 pores spongocoel out of osculum o Inside 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 mesohyl o Gas exchange and waste removal can occur via diffusion o Other tasks are performed by cells called amoebocytes Most sponges are hermaphrodites (both male and female parts) o Eggs reside in mesohyl, fertilization occurs in mesohyl 33.2: Cnidarians -General characteristics Where the eumetazoa clade begins on the animal phylogeny Cnidarians include hydras, corals, and jellies Body plan o Diploblastic and radial o Contains a sac with a central digestive compartment called the gastrovascular cavity o Two variations Sessile polyp Polyps are cylindrical forms that adhere to the substrate by the aboral end of their body Motile medusa Medusa resembles 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 cavity o The 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 algae 33.3: Lophotrochozoans -General characteristics Where bilateria clade begins on animal phylogeny o Most bilaterians have a digestive tract with two openings (mouth and an anus) and a coelem o

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