mechanisms for evolution chapter 23. objectives objectives –state the hardy-weinburg theorem...
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ObjectivesObjectives– State the Hardy-Weinburg theoremState the Hardy-Weinburg theorem– Write the Hardy-Weinburg equation and be Write the Hardy-Weinburg equation and be
able to use it to calculate allele and genotype able to use it to calculate allele and genotype frequenciesfrequencies
– List the conditions that must be met to maintain List the conditions that must be met to maintain Hardy Weinburg equilibriumHardy Weinburg equilibrium
VOCABULARYVOCABULARY
POPULATIONPOPULATION SPECIESSPECIES GENE POOLGENE POOL GENE FLOWGENE FLOW BOTTLENECK BOTTLENECK
EFFECTEFFECT FOUNDER EFFECTFOUNDER EFFECT HETEROZYGOTE HETEROZYGOTE
ADVANTAGEADVANTAGE
HYBRID VIGORHYBRID VIGOR STABILIZING STABILIZING
SELECTIONSELECTION DIRECTIONAL DIRECTIONAL
SELECTIONSELECTION DIVERSIFYING DIVERSIFYING
SELECTIONSELECTION SEXUAL SEXUAL
DIMORPHISMDIMORPHISM
POPULATIONPOPULATION– Localized group belonging to the same speciesLocalized group belonging to the same species
SPECIESSPECIES– Naturally breeding group of organisms that Naturally breeding group of organisms that
produce fertile offspringproduce fertile offspring GENE POOLGENE POOL
– Total aggregate of genes in a population at any Total aggregate of genes in a population at any one timeone time
Most species are not evenly distributed over a Most species are not evenly distributed over a geographic range. Individuals are more likely geographic range. Individuals are more likely to breed with others from their population to breed with others from their population centercenter
HARDY – WEINBURG THEOREMHARDY – WEINBURG THEOREM
Describes a NON-EVOLVING populationDescribes a NON-EVOLVING population In the absence of other factors the In the absence of other factors the
segregation and recombination of alleles segregation and recombination of alleles during meiosis and fertilization will not during meiosis and fertilization will not alter the overall genetic make-up of a alter the overall genetic make-up of a populationpopulation
Imagine an isolated Imagine an isolated wildflower population wildflower population with the following with the following characteristicscharacteristics– Diploid with both pink Diploid with both pink
and white flowersand white flowers
– Pink is dominant A and Pink is dominant A and white is recessive awhite is recessive a
– There are 480 pink There are 480 pink flowers and 20 whiteflowers and 20 white
» 320 are AA320 are AA
» 160 are Aa160 are Aa
(p + q)2 = 1
p + q = 1
p2 + 2pq +q2 = 1
pp22 = frequency of AA = frequency of AA 2pq = frequency of Aa2pq = frequency of Aa qq22 = frequency of aa = frequency of aa Calculate qCalculate q2 2 firstfirst There are 1000 allelesThere are 1000 alleles
– AA -- 320 x 2/plant = 640AA -- 320 x 2/plant = 640– Aa --160 x 1/plant =Aa --160 x 1/plant = 160 160
800800– aa -- 20 x 2/plant = 40aa -- 20 x 2/plant = 40– Aa – 160 x 1/plant =Aa – 160 x 1/plant =160160– 200200– Frequency of A = 80% and a = 20%Frequency of A = 80% and a = 20%
Condition for Hardy-WeinburgCondition for Hardy-Weinburg
Large populationLarge population No net mutationNo net mutation Isolated populationIsolated population Random matingRandom mating No natural selectionNo natural selection
CAUSES OF CAUSES OF MICROEVOLUTIONMICROEVOLUTION
GENETIC DRIFTGENETIC DRIFT
– BOTTLENECK EFFECTBOTTLENECK EFFECT
– FOUNDER EFFECTFOUNDER EFFECT
GENE FLOW – genetic exchange GENE FLOW – genetic exchange between populations due to migrationbetween populations due to migration
Mutation – a new mutation that is Mutation – a new mutation that is transmitted in a gamete can immediately transmitted in a gamete can immediately change the gene poolchange the gene pool
NONRANDON MATINGNONRANDON MATING– Breed with other members of the Breed with other members of the
“neighborhood” promotes inbreeding“neighborhood” promotes inbreeding– Assortative mating – mate with others like Assortative mating – mate with others like
themselvesthemselves NATURAL SELECTIONNATURAL SELECTION
Variation within PopulationsVariation within Populations
Most heritable variation is measured byMost heritable variation is measured by– Quantitative characters (vary along a Quantitative characters (vary along a
continuum ie. Height) are polygeneticcontinuum ie. Height) are polygenetic– Discrete characters (pink or white) are Discrete characters (pink or white) are
located on a single genelocated on a single gene
Polymorphism – two or more forms of a Polymorphism – two or more forms of a discrete character are represented in a discrete character are represented in a populationpopulation
GEOGRAPHICAL GEOGRAPHICAL VARIATIONVARIATION
A cline is a graded change in some trait along a geographical axis.