Chapter 22: Evolution (Lecture 1 Notes)

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Published on 9 Mar 2011
Biological Sciences
BIOA02: Dr. K. Persaud
Lecture #17 (Video)
Chapter 22: Mechanisms of Evolution
Mechanisms of Evolution
Charles Darwin was the first to formulize evolution, without the use of genes, etc
oHe was interested in the world around him, he loved nature, exploring, and
looking at the biological systems around him (plants and animals)
oHe wanted to have time to himself to explore the world around him
oHe was asked to be a ship HMS Beigels naturalist: someone who knew about
nature and would document what the nature of the place they went to
oHe made records of what he saw and observed
oThey stopped at the Galapagos Islands each island differs slightly in terms
of species (form) and plants etc
oClassic example of his arrangement: beak of the finch differed from island to
island, but same species
oHe hypothesized that there was one main ancestor, but over tmie they became
different because the islands were different (in terms of vegetation and
oHe didnt know the mechanisms of change, but he knew they existed
oLater on during the years he came up with natural selection
A controversial book came out by Thomas Malthus which scripted that he could
calculate the human population exponentially
oSome things keep up in check and under control disease, famine, etc 
necessary for human growth
oArtificial selection: people knew that they could reproduce certain traits by
mating selection
oVariation in populationdifferent individuals with different traits
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Document Summary

 adaptation: particular structure, physiological process or behavior that makes an organism better able to survive and reproduce. Also the processes that leads to the persistence of that trait.  most characteristics are influences by alleles at more than one locus.  show quantitative variation instead of qualitative (eg: height)  natural section in 3 ways: stabilizing selection: preserves average phenotype.  one mean value of a trait that does the best suited in its environemtn and reproduce successfully.  ex: human birth weight  varies but there is optimal: directional selection: favors individuals that vary in one direction.  adaptations to environement (geographic reasons, global warming, nomadism moving from one place to another, etc)  shift in alleles that adapt to the environment they are in: disruptive selection: from the average favors individuals that vary in opposite directions.  variation is created when individuals at either extreme are more successful than average individuals.