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CH 17 -- Processes of Evolution Genetic Equilibrium allele frequencies remain constant in a population at genetic equilibrium Genetic Equilibrium if the allele frequencies change from one generation to the next, the population is evolving Evolving Populations Natural selection determines the alleles that are most fit. Two examples of selection the peppered moth warfarin resistant rats Natural Selection in Action Peppered Moth wide range of speckle patterns spend daytime at rest on tree trunks and branches prey for birds Natural Selection in Action What factor or factors in the environment “selected” for the darker moths? Natural Selection in Action Rat Poison warfarin blocks a protein needed for blood clotting one allele of the gene coding for this protein makes a mutant protein that is not as good for clotting, but is insensitive to warfarin. Natural Selection in Action Allopatric Speciation Macro Evolution Over LONG time spans -- species diverge enough to form separate species, separate lineages. Many processes may be involved -mutations and changes in allele frequenceis mass extinctions adaptive radiations and others Evolutionary Relationships Hypothesis: All life on Earth is Descended from One Common Ancestor. earthworm multicellular tuna multicellular with a backbone lizard multicellular with a backbone and legs mouse multicellular with a backbone, legs, and hair human CH 18 -- Early Evolution How did life on earth evolve? electrodes CH4 NH3 H2O H2 spark discharge gases water droplets boiling water water containing organic compounds Endosymbiont Theory ancestral prokaryote infoldings of the plasma membrane infoldings evolve into the nuclear envelope and endomembrane system DNA aerobic bacteria are engulfed or infect the cell aerobic bacteria evolve into mitochondria photosynthetic bacteria Eukaryotic cells: animals, fungi, some protists Eukaryotic cells: plants, some protists engulfed photosynthetic bacteria evolve into chloroplasts Endosymbiont Theory Evidence -some features of mitochondria and chloroplasts are more similar to prokaryotes than to eukaryotes. 1) they have their own circular DNA 2) reproduce by binary fission 3) ribosomes are similar to prokaryotic 4) codon usage similar to prokaryotes 5) inner membrane similar to prokaryote plasma membrane Evolutionary Relationships Evolutionary Relationships BACTERIA ARCHAEA common ancestor EUKARYA Learning Outcomes Describe genetic equilibrium. Explain directional selection and how changes in peppered moths and warfarin resistant rats provide evidence of this process. Describe how speciation can occur using allopatric speciation as an example. Explain ideas about formation of organic molecules in earth’s early atmosphere. Explain the endosymbiont theory and evidence supporting it.
