01:119:101 Lecture Notes - Lecture 4: Gastrulation, Gnathostomata, Internal Fertilization
25 Feb 2016
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Unikont diversity iii: invertebrates ch 33, lack backbone, 95% of animal species, found throughout our animal phylogenetic tree. Sponges: structure, simple, multicellular, specialized cells, but not tissues and organs, asymmetric cannot cut them and get two mirror images, typical simple sponge, sac-like body, osculum- open end, spongocoel. Central cavity of the organism ; cavity acts as a passage for water. It is not digestive chamber: choanocytes = collar cells. Collar of microvilli at one end ; line spongocoel. Actual cells that will take up food particles. Fig 34. 4: oldest lineages in clade eumetazoa. One of the first branches that come off tree: mostly marine organisms. Ex: jellies (jelly fish ), coral: characteristics, radial symmetry, diploblastic, body structure, hollow sac ; mouth and tentacles, mouth only opening, gastrovascular cavity- digestive compartment, cnidocytes in tentacles. Function in defense and capturing prey: nematocysts. Produce a thread that is able to shoot out and penetrate into a body wall.
