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