Bio1B Evolution 2 Last lecture Introduction to Craig lecture outline Foundations Pre Darwinian background Darwin early influences Beagle voyage Wallace Today Descent with modification Natural selection principles lines of evidence Estimation interpretation of phylogeny Homology principles of phylogenetics The molecular clock On line resources Understanding Evolution UCMP http evolution berkeley edu Tree of life www tolweb org tree time Descent with modification The only figure in Origin of the species The Darwin Wallace principle of Natural selection Individuals within a population vary for one or more characteristics traits Traits are to some extent inherited by offspring from their parents More offspring are produced than can survive those with traits that improve survival reproduction leave more offspring these favorable traits will accumulate in the population over generations Lines of evidence in the Origin of the species by means of natural selection Darwin 1859 Artificial selection as analogy to natural selection Biogeography Nested geographic distributions Homology of traits modified for different purposes Population pressure Fig 22 10 Homology e g forearm elements of convergent wings of bats birds Fig 16 2 Fig 22 18 Anatomical homologies of embryos Pharyngeal pouches Post anal tail Human embryo Chick embryo Fish gills Pharangeal pouches Mammals ears throat Molecular homologies new insights invisible to Darwin Genetic code Transcription translation machinery Colinear segmentation Hox genes etc etc Fig 14 15 The current view of the phylogenetic hierarchy Understanding Evolution web site cf Aristotle s scala naturae See also Figs 19 1 20 3 in text Clades Represent All the Descendants of a Common Ancestor fig 16 3 Relationships are inferred from the distribution of shared derived traits Fig 16 3 Classification is based on monophyletic not polyphyletic or paraphyletic groups Fig 16 11 DNA sequence variation Fitting observed patterns of sequence variation at homologous aligned sites to a phylogenetic hypothesis The molecular clock dating divergence events Hemoglobin and divergence of chimpanzee human lineages Fig 16 9 Dating the emergence of HIV Fig 16 10
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