BIOL 202 Lecture Notes - Lecture 4: Sponge, Ctenophora, Choanoflagellate
20 Jan 2016
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Document Summary
No division of labour, communication, or coordination. Specialization in function lead to morphological changes. Formation of septa to divide cells with 1 nucleus: ancestral group of metazoans likely the choanoflagellates, 3 phyla. Lower metazoans: earliest multicellular organisms, hypotheses for origin of multicellularity. Colonial: simplest of the metazoans, parazoans beside the animals (subkingdom of animalia, 4 cell types (demonstrates division of labour) Porocytes contractile to control water flow. Choanocytes pumping water, directing nutrients to amoebocytes. Amoebocytes carry nutrients in organism, reproduction. Can aid in locomotion (if shot simultaneously) Can contain toxic chemicals: nerve net sensory cell connected to influence hydrostatic, medusa form = reproductive, mobile (jellyfish) skeleton. Some species have lost medusa stage: polyp form = sessile, predate other invertebrates, or are herbivorous, form symbioses with algae or dinoflagellates, species examples: Flourish in warmer environment bioproduction increases, they have more food.
