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Unit OneUnit OneEvolution and GeneticsChapters 20, 21, and 22
Genes Within Genes Within PopulationsPopulations
Chapter 20
DarwinDarwin• British Naturalist• Theory of Natural
Selection
Nuts and Bolts of the Nuts and Bolts of the TheoryTheory
• Species accumulate differences over time• Individuals pass on their traits• Descendants differ from ancestors• New species can therefore arise from old species
Major Agent of Major Agent of ChangeChange
• Not all organisms are the same• Some organism’s differences are better
adaptations• Better adaptations are passed on• Populations gradually change• Populations are better adapted to LOCAL
circumstances
Measuring Measuring allele allele
frequenciesfrequencies
• Approach #1o Electrophoresis to
separate proteins RFLP’s or SNP’s
• Approach #2oHardy-Weinberg
prediction
• Mutations
• Population genetics
Hardy-WeinbergHardy-Weinberg• Assumptions
o No mutation takes placeo No immigration or emigrationo Mating is randomo Population size is largeo No selection occurs
o Mr. Anderson Hardy-Weinberg
Five Agents of ChangeFive Agents of Change• Mutation changes alleles• Gene flow—when alleles move between
populations• Nonrandom mating shifts genotype frequencies• Genetic drift may alter allele frequencies in small
populations• Selection favors some genotypes over others
Did you notice anything Did you notice anything about the agents of about the agents of change and Hardy-change and Hardy-
Weinberg?Weinberg?Explain what you noticed.
Nonrandom matingNonrandom matingAssortative Mating Disassortative Mating
• Phenotypically similar organisms mate
• Essentially inbreeding
• Phenotypically different organisms mate
• Hybrids produced
Genetic Drift: Bottleneck Genetic Drift: Bottleneck EffectEffect
What types of scenarios could possibly cause this?
Genetic Drift: Founder EffectGenetic Drift: Founder Effect
What happened? Explain a mechanism whereby this could occur.
Bottleneck and Bottleneck and Founders Effect Founders Effect
ExamplesExamples• Northern Elephant
Seal• Amish communities
SelectionSelection• Phenotypic variation between individuals exist• Variation between individuals results in
differences of surviving offspring in the next generation
• Phenotypic variation has a genetic basis• Rock Pocket Mouse
Darwin’s FitnessDarwin’s Fitness• According to Darwin what is fitness?
Natural Selection Natural Selection RevisitedRevisited
• Negative frequency dependent selection• Positive frequency dependent selection• Oscillating selection
o Changes occur based on environmental pressureso Example in next chapter: finch beak shape due to precipitation
• Heterozygote advantageo Sickle cell anemia
Other Selection TypesOther Selection Types• Disruptive• Directional• Stabilizing
The Evidence for The Evidence for EvolutionEvolution
Chapter 21
Artificial Artificial SelectionSelection
Certain phenotypes are
favored
Russian FoxesRussian Foxes
Homologous Homologous StructuresStructures
Vestigial StructuresVestigial Structures
Convergence and Convergence and BiogeographyBiogeography
The Origin of SpeciesThe Origin of SpeciesChapter 22
Sympatric SpeciesSympatric Species• Phenotypically different• Utilize different habitats• Behave differently
SubspeciesSubspecies
Biological Species Biological Species ConceptConcept
• Sympatric species if they were to mate would become homogenized
• Ernst Mayr and the concepto Defines species as “…groups of actually or potentially interbreeding
natural breeding populations which are reproductively isolated from other such groups.”
o In other words, you must be able to reproduce and produce fertile offspring to be a species
• How could a species be reproductively isolated?
Geographic IsolationGeographic Isolation
Adaptive Adaptive RadiationRadiation
• Notable examples
include island habitats
• Hawaii
• Galapagos
Character Character displacementdisplacement
• A system where
individuals that do not
use the same resources
are favored by natural
selection
Micro and Micro and MacroevolutionMacroevolution
Stickleback Evolution