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Population Genetics The study of allele frequencies within a population.

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Presentation on theme: "Population Genetics The study of allele frequencies within a population."— Presentation transcript:

1 Population Genetics The study of allele frequencies within a population

2 Gene Pool All of the genes of a population of organisms –Organisms that are the most successful at reproducing contribute most to the gene pool

3 Evolution Any change in the frequency of any allele within a gene pool –Populations –Populations undergo evolution –Individuals –Individuals do not undergo evolution

4 Factors Affecting the Allele Frequency MutationMutation –Especially important for organisms with short generation times

5 Factors Affecting the Allele Frequency MigrationMigration –Movement of organisms into or out of the population

6 Factors Affecting the Allele Frequency Genetic DriftGenetic Drift –Random change in allele frequencies –Occurs mostly in small, isolated populations

7 Factors Affecting the Allele Frequency SelectionSelection –Environmental pressures –Competition –Climate change

8 Factors Affecting the Allele Frequency Nonrandom matingNonrandom mating –Preferences in selection of a mating partner

9 SPECIES Species Species: A group of organisms so similar to one another that they can interbreed and produce fertile offspring Kingdom Phylum Class Order Family Genus Species

10 Speciation SpeciationSpeciation is the evolution of new species through time SpeciationSpeciation occurs most rapidly in a small population

11 Mechanisms of Speciation Artificial SpeciationArtificial Speciation –New species have been developed by man Intentional mutations Cross breeding Genetic engineering

12 Mechanisms of Speciation Natural Speciation by Isolation of Small PopulationsNatural Speciation by Isolation of Small Populations –Geographical Isolation Geographical barriers separate two populations –Mountain ranges –Deep canyons –Bodies of water –Ecological Isolation Organisms of two populations require different habitats

13 Mechanisms of Speciation Behavioral IsolationBehavioral Isolation –Changes in habits that identify one population with another Mating rituals Methods of communication

14 Mechanisms of Speciation Seasonal IsolationSeasonal Isolation –Reproductive cycles do not coincide Plants that flower at different times Animals that mate or nest build at different times

15 Mechanisms of Speciation Mechanical IsolationMechanical Isolation –Physical characteristics that keep organisms from interbreeding Difference in size Difference in reproductive anatomy Inability of sperm to penetrate the egg

16 Observations From the Fossil Record Species often remain stable for millions of years with little or no noticeable change Species may disappear rapidly and new species may appear just as fast

17 Population Evolution

18 Punctuated Equilibrium Long periods of stability followed by short periods of rapid change


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