BIO 2135 Study Guide - Coelom, Endoskeleton, Respiratory System
1 Dec 2014
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Document Summary
Radial, about the axis of the mouth surface. Specialized cells (including chaonocytes and amoebocytes), but lack true tissues. Have true organs, with solid mass of mesodermal parenchyma cells surrounding organs. Metamerism - repetition of body parts (hearts, nephridia, reproductive organs) Cell layers separated by gel layer called mesenchyme. Two stages in the life cycle: free- swimming medusa stage and the sessile polyp stage. Use hemoglobin as respiratory pigment dissolved in blood (no red blood cells) Sinuses collect hemolymph and transport to ctenidia for gas exchange. Specialized cells called chaonocytes contain flagella that produce a current moving water through pores in body. Closed circulatory system (blood contained within vessels); dorsal blood vessel and ring-like hearts contract rhythmically. Gases diffuse via dermal branchiae; soluble wastes released by simple diffusion across surface epithelium. Open circulatory system; poorly-defined channels in coelomic cavity; lack heart; cilia associated with water vascular system circulate coelomic fluid. Can be hemimetabolous (like cockroach) or holometabolous (like fruit fly)
