Mechanisms of Mechanisms of Evolution & their Evolution & their

Effects on Effects on PopulationsPopulations

NEW VOCABULARYNEW VOCABULARY

•POPULATIONPOPULATION – GROUP OF – GROUP OF INDIVIDUALS OF SAME SPECIES INDIVIDUALS OF SAME SPECIES THAT INTERBREEDTHAT INTERBREED

•GENE POOLGENE POOL – COMMON GROUP – COMMON GROUP OF OF ALL GENES PRESENT IN A ALL GENES PRESENT IN A

POPULATIONPOPULATION

Gene PoolGene PoolCombined Combined

genetic info. genetic info. of all of all membersmembers

Allele frequency Allele frequency is # of times is # of times alleles occuralleles occur

A. Variation in A. Variation in PopulationsPopulations2 processes can 2 processes can

lead to this:lead to this:

MutationsMutations - -

change in DNA change in DNA

sequencesequence

Gene ShufflingGene Shuffling – –

from sexual from sexual

reproductionreproduction

B. Genetic Drift changes populations =B. Genetic Drift changes populations =

random change in allele random change in allele frequency causes an allele to frequency causes an allele to become commonbecome common

•B. Genetic Drift- B. Genetic Drift- Founder Effect:Founder Effect: a cause a cause of genetic drift of genetic drift attributable to attributable to colonization by a colonization by a limited number limited number of individuals of individuals from a parent from a parent populationpopulation

B. Genetic Drift- Bottleneck Effect:B. Genetic Drift- Bottleneck Effect:

= changes in gene distribution that = changes in gene distribution that result from a rapid decrease in result from a rapid decrease in population size.population size.

•C. Gene Flow (migration)C. Gene Flow (migration): genetic : genetic exchange due to the migration of exchange due to the migration of fertile individuals or gametes fertile individuals or gametes between populations (reduces between populations (reduces differences between populations)differences between populations)

D. Nonrandom matingD. Nonrandom mating: inbreeding : inbreeding and assortative mating (both shift and assortative mating (both shift frequencies of different genotypes)frequencies of different genotypes)

E. Natural E. Natural SelectionSelection: : differential differential success in success in reproduction; reproduction; only form of only form of microevolution microevolution that adapts a that adapts a population to its population to its environmentenvironment

F. Sexual selectionF. Sexual selection• Sexual Sexual

dimorphismdimorphism: : secondary sex secondary sex characteristic characteristic distinctiondistinction

• Sexual selectionSexual selection: : selection selection towards towards secondary sex secondary sex characteristics characteristics that leads to that leads to sexual sexual dimorphismdimorphism

Evolution of PopulationsEvolution of Populations

Occurs when Occurs when there is a there is a change in change in relative relative frequency of frequency of allelesalleles

Phenotype Phenotype ExpressionExpression•Depends on Depends on

how many how many genes genes control that control that traittrait

Single-Gene vs. Polygenic Single-Gene vs. Polygenic TraitsTraitsSingle-GeneSingle-Gene::

2 Distinct 2 Distinct PhenotypesPhenotypes

PolygenicPolygenic::

Many PhenotypesMany Phenotypes

(EG: tongue rolling)

Natural Selection- see handoutNatural Selection- see handout

•Shifts to Shifts to

middle rangemiddle range

•Shifts to Shifts to

2 extremes2 extremes

•Shifts to Shifts to

1 extreme1 extreme

Today:Today:

On page 359 of your text, answer #1-On page 359 of your text, answer #1-11.11.

Use this note & text pages 350-358 to Use this note & text pages 350-358 to help formulate your answers.help formulate your answers.