BIO 203 Lecture Notes - Lecture 34: Dinoflagellate, Myelin, Overfishing
1 Dec 2016
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Evolution of multicellular eukaryotes in michigan, ~2. 1 bya. Grypania spiralis first multicellular eukaryote, from banded iron formations. Burgess shale fauna all extant phyla and some that appear unrelated to. First appearances of many modern groups in fossils (arthropods, mollusks, vertebrates). Molecular evidence indicates they diverged with the ediacaran fauna. extant phyla. The sponges are comprised of 3 lineages: calcarea. Synapomorphy for the group, cellular body, with internal system of pores and canals. Porifera are sessile (cid:523)don"t move(cid:524) and depend on water currents to bring in food and oxygen and carry away wastes. Asymmetric: morphology changes with substrate, calmness of water, etc, vary from a few millimeters to 2 meters across; vary greatly in shape and color. They have a cellular level of organization. Cells are totipotent (capable of differentiation into other cell types: amoebocyte (what all cells start out as, porocyte, pinacocyte, choanocyte. Most of the 5000 poriferan species are marine; about 150 are freshwater.
