AIM: What are the overall factors causing evolution?

Warm-up: Briefly describe 2 mechanisms that could

account for speciation.

5 Agents of evolutionary change

5 Agents of evolutionary changeMutation

5 Agents of evolutionary changeMutation Gene Flow

5 Agents of evolutionary changeMutation Gene Flow Non-random mating

5 Agents of evolutionary changeMutation Gene Flow

Genetic Drift

Non-random mating

5 Agents of evolutionary changeMutation Gene Flow

Genetic Drift Selection

Non-random mating

1. Mutation & Variation

1. Mutation & Variation

1. Mutation & Variation

§Mutation creates variation

1. Mutation & Variation

§Mutation creates variationu new mutations are constantly appearing

1. Mutation & Variation

§Mutation creates variationu new mutations are constantly appearing

§Mutation changes DNA sequence

1. Mutation & Variation

§Mutation creates variationu new mutations are constantly appearing

§Mutation changes DNA sequenceu changes amino acid sequence

1. Mutation & Variation

§Mutation creates variationu new mutations are constantly appearing

§Mutation changes DNA sequenceu changes amino acid sequenceu changes protein

1. Mutation & Variation

§Mutation creates variationu new mutations are constantly appearing

§Mutation changes DNA sequenceu changes amino acid sequenceu changes proteinu changes in protein may

change phenotype & therefore change fitness

2. Gene Flow

2. Gene Flow

2. Gene Flow

§Movement of individuals & alleles in & out of populations

2. Gene Flow

§Movement of individuals & alleles in & out of populationsu seed & pollen distribution by

wind & insect

2. Gene Flow

§Movement of individuals & alleles in & out of populationsu seed & pollen distribution by

wind & insectu migration of animals

2. Gene Flow

§Movement of individuals & alleles in & out of populationsu seed & pollen distribution by

wind & insectu migration of animals§ sub-populations may have

different allele frequencies

2. Gene Flow

§Movement of individuals & alleles in & out of populationsu seed & pollen distribution by

wind & insectu migration of animals§ sub-populations may have

different allele frequencies

§ causes genetic mixing across regions

2. Gene Flow

§Movement of individuals & alleles in & out of populationsu seed & pollen distribution by

wind & insectu migration of animals§ sub-populations may have

different allele frequencies

§ causes genetic mixing across regions

§ reduce differences between populations

Human evolution today§ Gene flow in human

populations is increasing todayu transferring alleles

between populations

Human evolution today§ Gene flow in human

populations is increasing todayu transferring alleles

between populations

Human evolution today§ Gene flow in human

populations is increasing todayu transferring alleles

between populations

Are we moving towards a blended world?

3. Non-random mating

§ Sexual selection

3. Non-random mating

§ Sexual selection

4. Genetic drift

4. Genetic drift

4. Genetic drift

§ Effect of chance events

4. Genetic drift

§ Effect of chance eventsu founder effect

4. Genetic drift

§ Effect of chance eventsu founder effect§ small group splinters off & starts a new colony

Warbler

finch

Tree

finc

hes

Ground finches

4. Genetic drift

§ Effect of chance eventsu founder effect§ small group splinters off & starts a new colony

Warbler

finch

Tree

finc

hes

Ground finches

4. Genetic drift

§ Effect of chance eventsu founder effect§ small group splinters off & starts a new colony

u bottleneck

Warbler

finch

Tree

finc

hes

Ground finches

4. Genetic drift

§ Effect of chance eventsu founder effect§ small group splinters off & starts a new colony

u bottleneck § some factor (disaster) reduces population to

small number & then population recovers & expands again

Warbler

finch

Tree

finc

hes

Ground finches

4. Genetic drift

§ Effect of chance eventsu founder effect§ small group splinters off & starts a new colony

u bottleneck § some factor (disaster) reduces population to

small number & then population recovers & expands again

Founder effect

Founder effect

§When a new population is started by only a few individualsu some rare alleles may be at high

frequency; others may be missing

u skew the gene pool of new population§ human populations that

started from small group of colonists

§ example: colonization of New World

Distribution of blood types§ Distribution of the O type blood allele in native

populations of the world reflects original settlement

Distribution of blood types§ Distribution of the O type blood allele in native

populations of the world reflects original settlement

Distribution of blood types§ Distribution of the O type blood allele in native

populations of the world reflects original settlement

Distribution of blood types§ Distribution of the B type blood allele in native

populations of the world reflects original migration

Distribution of blood types§ Distribution of the B type blood allele in native

populations of the world reflects original migration

Distribution of blood types§ Distribution of the B type blood allele in native

populations of the world reflects original migration

Distribution of blood types§ Distribution of the B type blood allele in native

populations of the world reflects original migration

Bottleneck effect

Bottleneck effect

§When large population is drastically reduced by a disaster

Bottleneck effect

§When large population is drastically reduced by a disasteru famine, natural disaster, loss of habitat…

Bottleneck effect

§When large population is drastically reduced by a disasteru famine, natural disaster, loss of habitat…u loss of variation by chance event

Bottleneck effect

§When large population is drastically reduced by a disasteru famine, natural disaster, loss of habitat…u loss of variation by chance event§ alleles lost from gene pool

Bottleneck effect

§When large population is drastically reduced by a disasteru famine, natural disaster, loss of habitat…u loss of variation by chance event§ alleles lost from gene poolwnot due to fitness

Bottleneck effect

§When large population is drastically reduced by a disasteru famine, natural disaster, loss of habitat…u loss of variation by chance event§ alleles lost from gene poolwnot due to fitness

§ narrows the gene pool

Cheetahs

Cheetahs

§ All cheetahs share a small number of alleles

Cheetahs

§ All cheetahs share a small number of allelesu less than 1% diversity

Cheetahs

§ All cheetahs share a small number of allelesu less than 1% diversityu as if all cheetahs are

identical twins

Cheetahs

§ All cheetahs share a small number of allelesu less than 1% diversityu as if all cheetahs are

identical twins

§ 2 bottlenecks

Cheetahs

§ All cheetahs share a small number of allelesu less than 1% diversityu as if all cheetahs are

identical twins

§ 2 bottlenecksu 10,000 years ago

Cheetahs

§ All cheetahs share a small number of allelesu less than 1% diversityu as if all cheetahs are

identical twins

§ 2 bottlenecksu 10,000 years ago§ Ice Age

Cheetahs

§ All cheetahs share a small number of allelesu less than 1% diversityu as if all cheetahs are

identical twins

§ 2 bottlenecksu 10,000 years ago§ Ice Age

u last 100 years

Cheetahs

§ All cheetahs share a small number of allelesu less than 1% diversityu as if all cheetahs are

identical twins

§ 2 bottlenecksu 10,000 years ago§ Ice Age

u last 100 years§ poaching & loss of habitat

Conservation issuesPeregrine Falcon

Golden Lion Tamarin

Conservation issues§ Bottlenecking is an important

concept in conservation biology of endangered species

Peregrine Falcon

Golden Lion Tamarin

Conservation issues§ Bottlenecking is an important

concept in conservation biology of endangered speciesu loss of alleles from gene pool

Peregrine Falcon

Golden Lion Tamarin

Conservation issues§ Bottlenecking is an important

concept in conservation biology of endangered speciesu loss of alleles from gene poolu reduces variation

Peregrine Falcon

Golden Lion Tamarin

Conservation issues§ Bottlenecking is an important

concept in conservation biology of endangered speciesu loss of alleles from gene poolu reduces variationu reduces adaptability

Breeding programs must consciously outcross

Peregrine Falcon

Golden Lion Tamarin

5. Natural selection

5. Natural selection

§ Differential survival & reproduction due to changing environmental conditions

5. Natural selection

§ Differential survival & reproduction due to changing environmental conditions

§ climate change

5. Natural selection

§ Differential survival & reproduction due to changing environmental conditions

§ climate change§ food source availability

5. Natural selection

§ Differential survival & reproduction due to changing environmental conditions

§ climate change§ food source availability

§ predators, parasites, diseases

5. Natural selection

§ Differential survival & reproduction due to changing environmental conditions

§ climate change§ food source availability

§ predators, parasites, diseases§ toxins

5. Natural selection

§ Differential survival & reproduction due to changing environmental conditions

§ climate change§ food source availability

§ predators, parasites, diseases§ toxins

u combinations of alleles that provide “fitness” increase in the population

5. Natural selection

§ Differential survival & reproduction due to changing environmental conditions

§ climate change§ food source availability

§ predators, parasites, diseases§ toxins

u combinations of alleles that provide “fitness” increase in the population§ adaptive evolutionary change