Chapter 33

Chapter 33 - Chapter 33 Invertebrates 1) Sponges are...

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Chapter 33 – Invertebrates 1) Sponges are sessile and have a porous body and choanocytes a) Phylum Porifera i) Live in both fresh and marine waters ii) Lack true tissues and organs iii) Asymmetrical body plan b) Sponges are suspension feeders i) Filter water passing through their body 2) Cnidarians have radial symmetry, a gastrovascular cavity, and cnidocytes a) A wide range of sessile and floating forms including jellyfish, corals, and hydras b) Simple diploblastic, radial body plan i) Body plan is a sac with a central gastrovascular cavity ii) Single opening serves as both mouth and anus iii) Mesoglea layer between epidermis and endodermis (gastrodermis) c) Cnidarians body plans i) Polyp form is generally sessile ii) Medusa form moves freely in water by passive drifting and contractions of the bell d) Defining features of Cnidarians i) Cnidocytes (1) Unique cells that function in defense and the capture of prey ii) Stimulus causes the cell to evert releasing thread iii) Some cnidocytes sting, others just entangle prey 3) Most animals have bilateral symmetry a) Most animals belong to the bilateria clade i) Bilateral symmetry (1) Cephalization
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ii) Triploblastic development (1) Ectoderm – outer layer (2) Mesoderm – middle layer
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This note was uploaded on 02/04/2009 for the course BIOL 1202 taught by Professor Gregg during the Spring '08 term at LSU.

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Chapter 33 - Chapter 33 Invertebrates 1) Sponges are...

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