i) Artificial selectionii) Variation in natural speciesiii) Struggle for existenceiv) Natural selectionBio1b Summer 2008 Evolution Lecture 2Eric Harris Page 1 of 3EVOLUTION LECTURE 2: DARWIN AND THE GENETIC BASIS OF EVOLUTIONReading: 7th ed., 443–453, 251–260; 8th ed., 457–467, 262–271. A. Recap of Pre-Darwinian ideas of EvolutionB. The argument presented in “On the Origin of Species” (1859)i) Artificial selectionii) Variation in natural speciesiii) Struggle for existenceiv) Natural selectionC. Problems for Darwin’s Theoryi) ‘Blending’ theory of inheritance ii) How can selection recognize such small differences?iii) Is the earth old enough? iv) Lack of transitional formsD. Evidence of Evolutioni) Artificial selectionii) Systematicsiii) Geographical Distributions (Biogeography)iv) Comparative AnatomyHomology, Vestigial Structures, Rudimentary organsv) Comparative Embryologyvi) FossilsUpdated on 06/17/08Bio1b Summer 2008 Evolution Lecture 2Eric Harris Page 2 of 3vii) Molecular biology (in recent years)Darwin presented overwhelming evidence for evolution having occurred and a specificmechanism (natural selection) to explain how it occurred.Remember: i) Individuals do not evolve, populations doii) Natural selection can only amplify HERITABLE variationiii) Not all variation is heritable, much of it is environmentalE. Mendelian genetics – terms to remember: character, true-breeding, trait, P, F1, F2, homozygous, heterozygous, genotype, phenotype, monohybrid cross, dihybrid cross, test-cross i) Mendel’s law of segregation (using modern terminology)Allele pairs segregate during gamete formation (meiosis), and the paired condition is restored by the random fusion of gametes at fertilization.ii) Mendel’s law of independent assortment (using modern terminology)Each allele pair segregates independently of other gene pairs during gamete formation.iii) Mendelian genetics involve the application of these two simple laws and two basic laws of probability.Rule of multiplication – the probability that independent events will occur simultaneously is the product of their individual probabilities.Updated on 06/17/08Bio1b Summer 2008 Evolution Lecture 2Eric Harris Page 3 of 3Rule of addition – the probability that an event can occur in two or more independent ways is the sum of the separate probabilities of the different ways.Updated on
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