Analyze and evaluate the effects of other evolutionary mechanisms, including genetic drift, gene flow, mutation, and recombination.

Unit 117F

Let’s remember…

• An allele is an alternative form of one gene

B stands for black b stands for brown

The allele would be…

Genetic Drift

• An evolutionary mechanism in which allele frequencies change in a population

Allele frequency changes due to…

• Natural disaster like flood, fire, or earthquake• A random change of the

population (some are eliminated)• Different from natural selection

b/c its by chance or randomly

Original Pop

R = red star r = green heart

Pop after change

6R, 5r 5r

http://www.google.com/url?sa=i&rct=j&q=genetic+drift&source=images&cd=&cad=rja&docid=ahwhAuczEEK9bM&tbnid=JKtd5bKpCW7DiM:&ved=0CAUQjRw&url=http://legacy.hopkinsville.kctcs.edu/sitecore/instructors/Jason-Arnold/VLI/Module%203/Module3Evolution/Module3Evolution7.html&ei=-NYaUfimD8LfyAGw5YDgCQ&bvm=bv.42261806,d.aWc&psig=AFQjCNGnvXDF2DFzuU1LF2LBAWD0UG2YLw&ust=1360799853869501

http://www.google.com/url?sa=i&rct=j&q=genetic+drift&source=images&cd=&cad=rja&docid=cF7FEBn_rBIBoM&tbnid=g9xu5pultJvDBM:&ved=0CAUQjRw&url=http://www.cssforum.com.pk/css-optional-subjects/group-d/zoology/14536-notes-zoology-15.html&ei=VdcaUZyiF6aIygGhpoCwAQ&bvm=bv.42261806,d.aWc&psig=AFQjCNGnvXDF2DFzuU1LF2LBAWD0UG2YLw&ust=1360799853869501

Bottleneck Effect

• The change in allele frequency where only genes of the surviving population members can be passed to future generations

http://www.google.com/url?sa=i&rct=j&q=genetic+drift&source=images&cd=&cad=rja&docid=MAr_RFPfkWMM8M&tbnid=33SazISehqdGgM:&ved=0CAUQjRw&url=http://waynesword.palomar.edu/lmexer6.htm&ei=u9gaUd2PFdH-2QXX-4FY&bvm=bv.42261806,d.aWc&psig=AFQjCNGnvXDF2DFzuU1LF2LBAWD0UG2YLw&ust=1360799853869501

http://www.google.com/url?sa=i&rct=j&q=genetic+drift&source=images&cd=&cad=rja&docid=h_vEi5mogExblM&tbnid=fKSSjhrywHw1pM:&ved=0CAUQjRw&url=http://nilevalleypeoples.blogspot.com/2012/12/demic-diffusion-notes-and-tropical.html&ei=2tcaUdmwB4GGyAHPh4CYDw&bvm=bv.42261806,d.aWc&psig=AFQjCNGnvXDF2DFzuU1LF2LBAWD0UG2YLw&ust=1360799853869501

Gene Pool

• the sum of all the genes in an interbreeding population

Gene Pool

• 2 blue alleles• 1 red allele• 12 green alleles

http://www.google.com/url?sa=i&rct=j&q=emigration+genetic+drift&source=images&cd=&cad=rja&docid=lBjm4mRsMnkl7M&tbnid=me52ChBbte9LUM:&ved=0CAUQjRw&url=http://www.phschool.com/science/biology_place/labbench/lab8/breedpop.html&ei=cdkaUa3VMOWg2QWRx4D4Aw&bvm=bv.42261806,d.aWc&psig=AFQjCNHK86mLpYiRLA48RjvK-vchxLlorg&ust=1360800384841404

Founder Effect

• The change in allele frequency in a gene pool that changes from a large population to a small population• Ex: small number of individuals get

separated from a larger population… the change in the allele frequency is the founder effect

http://www.google.com/url?sa=i&rct=j&q=founder+effect&source=images&cd=&cad=rja&docid=Nl81GL5sM9KP-M&tbnid=77l54uAJ5MCTkM:&ved=0CAUQjRw&url=http://www.umbc.edu/bioclass/biol100/powerpoints/lecture10/sld032.htm&ei=PN4aUZCaFaHI2AXWh4DQBg&bvm=bv.42261806,d.aWc&psig=AFQjCNF_gBagVweofaP_q2V6EbeTTScWMg&ust=1360801671481332

Founder Effect

Gene Flow

• Occurs when the genes of 1 population flow into a different population• This change causes a shift in allele

frequency

Immigration• Alleles move INTO a population

Emigration

• Alleles move OUT OF a population

Lots of gene flow…

• Slows down evolution• Lots of new alleles coming into

and out of a population• More genetic variation within a

population• Makes 2 populations more similar

Lack of gene flow…

• Less variation within a population• Makes 2 populations more

different and separates them

Mutation

• Any change in the genetic material of a cell• Can occur within individual genes

OR• Can involve changes in piece of

chromosomes

• If the mutation is beneficial to the organism, the mutation will be passed on to offspring • Slowly over time the mutation

will become more common in a population

Recombination

• A source of heritable variation• Occurs for 2 reasons:a. Independent assortmentb. Crossing over

Independent Assortment

Crossing Over

Hardy-Weinberg Principle

• States that allele frequencies in a population will remain constant unless one ore more factors cause those frequencies to change

Hardy-Weinberg Equation

P2 + 2pq + q2 = 1

Homozygous dominant

Homozygous recessive

Heterozygous

p = dominant allele frequency q = recessive allele frequency

Genetic Equilibrium

• The situation in which allele frequencies remain constant (don’t change)• If frequencies don’t change, the

population doesn't evolve

Conditions required to maintain genetic equilibrium:

1. Random mating2. Population must be large3. No immigration or emigration4. No mutations5. No natural selection