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Lecture 6

BIOL215 Lecture 6 Notes.pdf

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Biology (Sci)
BIOL 215
Neil Price

BIOL215 Lecture 6 Notes Multicellularity is not a directional thing. It evolved at least 13 times independently. It obviously must be a good solution for adaptive problems Common advantages of multicellularity as discussed in class: •Complex coordination of movement •Absorb more food •Can become larger •Chance of survival increases •Can stick to the surface •Specialization of cells Multicellularity evolved because: •Aquatic: • Mutation allowed them to stick to ideal substrate? (some cells fail to divide and therefore, they grow together - allowing them to stick to substrate) • Increase in size preventing filter feeders from eating (volvox) • Faster swimming capability •Terrestrial: • Dispersal of spores, cysts Feeding • • Creates an internal environment less environmental hetrogeneity Summary: •Learn 3 important principles in Evolutionary Biology: • Inferring evolutionary history - principle of phylogeny • Independent evolution (the idea that a trait can evolve independently) • Evolutionary bias - is there direction in evolution? •Phylogenies and the transition from unicellular to multicellular organisms Consequences of independent evolution as discussed in class: •Large variety of species - radiation of successful organisms •Save on energy Evolutionary inventions can cause adaptive radiations Adaptive Radiation: evolutionary divergence of members of a single phylogenetic lineage into a variety of different adaptive forms over a relatively short interval of geological time When the internal nodes and internal branches are very short, and the terminal branches are very long, this is a signature sign of an adaptive radiation (comes out looking like a comb) How/Why adaptive radiations: •Different environmental conditions •Increase diversity of food nutrients •Acquired the ability to reach a new food source •Mutation agents - greater number of mutations in the linage and increased rate of evolution •Fill previously unavailable niches Competitive release - two organisms side by side with one being dominant causing other to be • extinct • Competitive advantage - transition from water to land See the geological timescale (Table 18.2 in textbook) - remember the information that are underlined In 25 million years, the "Big Bang Explosion" (Cambrian Explosion) occurred gave rise to 35 different phyla of animals 505 mya: Cambrian Explosion (Paleozoic Era) - "explosion" of sponges, worms, jellyfish, "small shelly fossils;" ancestors to all modern animal groups appear 435 mya (Ordovician): Jawless fishes; first land plants 410 mya (Silurian): First vascular plants & first fish with jaws, 360 mya (Devonian): Bony fishes See va
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