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Lecture 6

BIOL 215 Lecture Notes - Lecture 6: Molecular Clock, Carboniferous, Burgess Shale

Biology (Sci)
Course Code
BIOL 215
Neil Price

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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:
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
Dispersal of spores, cysts
Creates an internal environment less environmental hetrogeneity
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
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