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Darwin

BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection. Darwin. 1835 _____________ visited the Galapagos Islands and became convinced various populations evolved from ancestral form.

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Darwin

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  1. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection Darwin • 1835 _____________visited the Galapagos Islands and became convinced various populations evolved from ancestral form. • 1838 After reading an essay by __________________, he theorized some individuals would have a competitive advantage conferred by favorable characteristics.

  2. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection Darwin’s Theory of Natural Selection • Some are heritable.

  3. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection • Augustinian Monk • Studied garden pea (Pisum sativum). • Discovered characteristics pass from parent to offspring in form of discrete packets called genes. • Exist in alternate forms - alleles. • Some prevent expression of others.

  4. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection Big Picture… • Phenotypic variation among individuals in a population results from the combined effects of …

  5. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection Big Picture… • The Hardy-Weinberg equilibrium model helps identify …

  6. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection Big Picture… • ________________ is differential survival and reproduction among phenotypes.

  7. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection Big Picture… • The extent to which phenotypic variation is due to genetic variation determines ….

  8. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection Big Picture… • Random processes, such as genetic drift, can…

  9. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection Variation Within Populations • Variation in Plant Populations • Many plant species differ dramatically in form from one elevation to another. • Clausen et al. found evidence of adaptation by ecotypes to local environmental conditions in Potentillaglandulosa.

  10. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection Variation Within Populations • Variation in Plant Populations • Phenotypic differences (growth and flower production) within clones grown at the 3 elevations are the result of environmental differences

  11. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection

  12. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection Variation in Animal Populations • Genetic Variation in Alpine Fish • Movement of cold adapted aquatic species into the headwaters of glacial valleys that lace the Alps created clusters of geographically isolated populations. • Douglas and Brunner used microsatellite DNA to conclude Coregonus populations are …

  13. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection Hardy Weinberg • Hardy Weinberg principle states that in a population mating at random in the absence of evolutionary forces, allele frequencies will remain constant.

  14. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection Calculating Gene Frequencies • SS (81%) SA (18%) AA (1%) • Frequency of S allele ? • =

  15. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection Conditions Necessary for Hardy Weinberg • …Between All Genotypes • Likely, at least one of these will not be met and allele frequencies will change. • Potential for evolutionary change in natural populations is very great.

  16. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection Natural Selection • Some individuals in a population, because of their phenotypic characteristics, will have higher survival and produce more offspring. • ________________is the measure of an individual’s contribution of offspring, or genes, to future generations. • Natural selection can…

  17. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection Stabilizing Selection • __________________ acts to impede changes in a population by acting against extreme phenotypes and favoring average phenotypes.

  18. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection Directional Selection • ____________________ leads to changes in phenotypes by favoring an extreme phenotype over other phenotypes in the population.

  19. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection Disruptive Selection • ________________ creates bimodal distributions by favoring two or more extreme phenotypes over the average phenotype in a population.

  20. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection Evolution by Natural Selection • Natural selection, which changes genotypic and phenotypic frequencies in populations, can result in adaptation to the environment. • Depends on ________________of trait. h2 = VG / VP • VG : Genetic variance • VP: Phenotypic variance

  21. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection Adaptive Change in Colonizing Lizards • Losos et al. • Genus Anolis • Great diversity includes large amount of variation in size and body proportions. • Length of hind limbs appears to reflect … • Diameter of perching surfaces.

  22. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection Rapid Adaptation by Soapberry Bugs • Carroll and Boyd • Soapberry Bug (Jaderahaematoloma) feeds on seeds from family Sapindaceae. • Slender beaks to pierce fruit walls. • Distance from outside fruit wall to seeds varies widely - … • Found close relationship between …

  23. Change Due To Chance BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection • Working in teams complete the simulation on Population Genetics…

  24. Change Due To Chance Random processes such as _____________ can change gene frequencies in populations, especially in small populations. Major concern of ____________________ is reducing habitat availability to the point where genetic drift will reduce genetic diversity within natural populations. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection

  25. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection Evidence of Genetic Drift in Chihuahua Spruce • Piceachihuahuana now restricted to peaks of Sierra Madre Occidental in N. Mexico. • Ledig et al. examined populations to determine if the species has lost genetic diversity as a consequence of reduced population size. • Found significant …

  26. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection Genetic Variation In Island Populations • In general, genetic variation is _________ in isolated and generally smaller, island populations. • Reduced genetic variation indicates a lower potential for a population to evolve.

  27. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection Genetic Diversity and Butterfly Extinctions • Frankham and Ralls point out ___________ may be a contributor to higher extinction rates in small populations. • Reduced fecundity, depressed juvenile survival, shortened life-span. • Saccheri et al. conducted genetic studies on populations of Glanville fritillary butterflies (Melitaceacinxia). • Populations with highest levels of inbreeding had…

  28. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection Evolution and Agriculture • “_____________________” is used to describe selective breeding of domesticated organisms to produce or maintain desirable traits. • “_____________________” is the introduction or deletion of genes in domesticated organisms. • These organisms are termed “genetically modified organisms” or GMOs.

  29. BIOL 3240 Plant and Animal Ecology – Population Genetics and Natural Selection Unintended Evolutionary Consequences • The use of chemicals in agriculture can have evolutionary consequences • Plant and animal pests may evolve resistance to the chemicals used to control them • Resistance among pests have been shown to be quick and widespread • Vila-Aiub et al. showed how Johnsongrass quickly evolved resistance to herbicides in Argentina

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