PopulationGenetics(KFogler)

8/7/2019 PopulationGenetics(KFogler)

1/23

2007-2008AP Biology

Evolution of Populations

Doonesbury - Sunday February 8, 2004Doonesbury - Sunday February 8, 2004


2/23

AP Biology

Populations evolve

Natural selection acts on individuals differential survival survival of the fittest

differential reproductive success who bears more offspring

Populations evolve genetic makeup of

population changesover time

favorable traits(greater fitness)

become more common

Presence of lactate

dehydrogenase

Mummichog


3/23

AP Biology

Changes in populations

Bent Grass on toxic mine sitePocket Mice in desert lava flows

Pesticidemolecule

Insect cellmembrane

Target site

Resistanttarget site

Insecticide resistance

Target site

Decreased number of target sites
http://biology%20textbook%20cds/Raven%20CD/chapter21/Powerpoint_Slides/chapter_21_powerpoint_i.ppthttp://biology%20textbook%20cds/Raven%20CD/chapter21/Powerpoint_Slides/chapter_21_powerpoint_i.ppthttp://biology%20textbook%20cds/Raven%20CD/chapter21/Powerpoint_Slides/chapter_21_powerpoint_i.ppthttp://biology%20textbook%20cds/Raven%20CD/chapter21/Powerpoint_Slides/chapter_21_powerpoint_i.ppthttp://biology%20textbook%20cds/Raven%20CD/chapter21/Powerpoint_Slides/chapter_21_powerpoint_i.ppthttp://biology%20textbook%20cds/Raven%20CD/chapter21/Powerpoint_Slides/chapter_21_powerpoint_i.ppthttp://biology%20textbook%20cds/Raven%20CD/chapter21/Powerpoint_Slides/chapter_21_powerpoint_i.ppthttp://biology%20textbook%20cds/Raven%20CD/chapter21/Powerpoint_Slides/chapter_21_powerpoint_i.ppthttp://biology%20textbook%20cds/Raven%20CD/chapter21/Powerpoint_Slides/chapter_21_powerpoint_i.ppt


4/23

2007-2008AP Biology

Individuals DONT evolve

Individuals survive or dont survive

Populations evolve

Individuals are selected

Individuals reproduce or dont


5/23

AP Biology

Fitness

Survival & Reproductivesuccess individuals with one

phenotype leave more

surviving offspring

Body size & egg laying in water striders


6/23

AP Biology

Variation & natural selection

Variation is the raw material for natural selection there have to be differences within population

some individuals must be more fit than others


7/23

AP Biology

Mean beak depth of parents (mm)

Medium ground finch8

8 9 10 11

9

10

11

1977 1980 1982 1984

Dry year

Dry year

Dry year

Wet year

Beakdepth

Beakdeptho

f

offspring(mm)

Where does Variation come from?

Mutation random changes to DNA

errors in mitosis & meiosis

environmental damage

Sex mixing of alleles

recombination of alleles

new arrangements in every offspring

new combinations = new phenotypes spreads variation

offspring inherit traits from parent


8/23

AP Biology

5 Agents of evolutionary changeMutation Gene Flow

Genetic Drift Selection

Non-random mating


9/23

AP Biology

1. Mutation & Variation

Mutation creates variation new mutations are constantly appearing

Mutation changes DNA sequence

changes amino acid sequence? changes protein? changes structure?

changes function?

changes in protein may

change phenotype &

therefore change fitness


10/23

AP Biology

2. Gene Flow

Movement of individuals &alleles in & out of populations seed & pollen distribution by

wind & insect migration of animals sub-populations may have

different allele frequencies

causes genetic mixingacross regions

reduce differences

between populations


11/23

AP Biology

Human evolution today

Gene flow in humanpopulations is

increasing today transferring alleles

between populations

Are we moving towards a blended world?Are we moving towards a blended world?


12/23

AP Biology

3. Non-random mating

Sexual selection


13/23

AP Biology

Warbler

finch

Tree

fin

ches

Groundfin

ches

4. Genetic drift

Effect ofchance events founder effect small group splinters off & starts a new colony

bottleneck some factor (disaster) reduces population to

small number & then population recovers &

expands again


14/23

AP Biology

Founder effect

When a new population is startedby only a few individuals some rare alleles may be at high

frequency; others maybe missing

skew the gene pool of

new population

human populations thatstarted from small group

of colonists

example:

colonization of New World


15/23

AP Biology

Distribution of blood types

Distribution of the O type blood allele in nativepopulations of the world reflects original settlement


16/23

AP Biology

Distribution of blood types

Distribution of the B type blood allele in nativepopulations of the world reflects original migration


17/23

AP Biology

Out of Africa

Likely migration paths of humans out of AfricaLikely migration paths of humans out of Africa

Many patterns of human traits reflect this migrationMany patterns of human traits reflect this migration

50,000ya

10-20,000ya

10-20,000ya


18/23

AP Biology

Bottleneck effect

When large population is drasticallyreduced by a disaster famine, natural disaster, loss of habitat

loss of variation by chance event alleles lost from gene pool not due to fitness

narrows the gene pool


19/23


20/23

AP Biology

Conservation issues

Bottlenecking is an importantconcept in conservation

biology of endangered

species loss of alleles from gene pool

reduces variation

reduces adaptability

Breeding programs must

consciously outcross

Breeding programs must

consciously outcross

Peregrine Falcon

Golden LionTamarin


21/23

AP Biology

5. Natural selection

Differential survival & reproduction dueto changing environmental conditions

climate change

food source availability

predators, parasites, diseases

toxins

combinations ofalleles

that provide fitnessincrease in the population adaptive evolutionary change


22/23

AP Biology

5 Agents of evolutionary changeMutation Gene Flow

Genetic Drift Selection

Non-random mating


23/23

2005-2006AP Biology

Any Questions??

Documents

PopulationGenetics(KFogler)