Lecture_2_Mechanisms_of_Evolution

Lecture_2_Mechanisms_of_Evolution - 6/15/2011 Evolution:...

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6/15/2011 1 Evolution: What and How LS1: Summer Session A June 22, 2011 “Nothing in biology makes sense except in the light of evolution.” Theodosius Dobzhansky March 1973 Theodosius Dobzhansky (1900-1975) Evolution… Shows the relatedness of all of life Explains the differences between organisms Explains how organisms can adapt to varied or changing environments Works on many levels from molecules to species What is evolution? Descent with modification Change in allele frequencies over time Charles Darwin No discussion of evolution would be complete without mentioning Charles Darwin But he was not the first to suggest that evolution occurred Pre-Evolution Aristotle’s Scala Naturae was the prevailing notion prior to Darwin’s Theory of Evolution by Natural Selection Species were fixed and immutable
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6/15/2011 2 Early ideas of evolution Georges-Louis Leclerc, Comte de Buffon (1707-1788) Jean-Baptiste de Monet, Chevalier de Lamarck (1744-1829) Buffon’s observations Buffon’s studies on animals showed anatomical similarity Despite a wide diversity of form and function, the basic bone architecture was the same Common ancestry? Lamarck’s ideas of evolution Lamarck believed that the use or disuse of traits could cause them to be altered over an individual’s lifetime He suggested these differences could be inherited by offspring Charles Darwin & The Origin Evolution as a concept was known in the pre- Darwinian world However, The Origin provided a suitable mechanism to explain how evolution could occur Darwin’s Voyage At age 22, Charles Darwin began a five- year, round-the-world voyage aboard the HMS Beagle In his role as ship’s naturalist, he collected and examined the species that inhabited the regions the ship visited Voyage of the Beagle
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6/15/2011 3 The Galapagos Islands Galapagos Finches Darwin’s observations Many species of finch on the Galapagos Islands Clearly from similar origin Why so different? Finches were clearly adapted to different lifestyles. How did they get that way? Darwin was a pigeon breeder and recognized the power of selective breeding Artificial Selection Darwin’s Contribution to Biology Darwin’s Theory of Evolution by Natural Selection Variation Heritability Differential reproductive success
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6/15/2011 4 Darwin’s Theory in a Nutshell Observation 1: All populations have the potential to grow exponentially Observation 2: A population does not grow exponentially Inference 1: There is a competition for resources Struggle for existence Thomas Malthus posited the idea that more individuals are born than can survive Thomas Robert Malthus, 1766-1834 Darwin’s Theory in a Nutshell
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Lecture_2_Mechanisms_of_Evolution - 6/15/2011 Evolution:...

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