Lamarck

Lamarck = Inheritance of acquired characteristics

Giraffe stretches neck over several generations to reach

leaves high in trees

Darwin

Natural selection – favorable new traits resulting from random mutations are passed on to succeeding generations

Darwin = Proposes the “Origin of Species”

(by natural selection)

5 year world cruise

leaves fruit

Vegetarian

grubs

cactus

Uses tools

Woodpecker

insectsinsects

seeds

seeds

Ancestor?

Darwin’s Finches

Ancestral bird “adapts” (by natural selection) into various habitats

Microevolution:Change in the gene frequency within a population

Provides new genetic material for new traits …… without which all life would look the same ….. like the first life.

Many bacteria, including resistant variety

Expose all bacteria to antibiotics;

most normal die

Resistant bacteria multiply

and dominate

Entire infection

evolves into resistant

strain

Normal bacteria

Resistant bacteria

Dead bacteria

Add Antibiotic

% R

ES

IST

AN

CE

Example of microevolution

Causes of microevolution:

1. Mutation – nucleotide or chromosome

2. Non random mating – mate selection

3. Gene Flow - migration

4. Genetic Drift – accidental loss of individuals

5. Natural Selection – most fit reproduce more often

UV light

Thymine dimer

Radiation (x-ray) causes chromosome damage

mutation No mutation

No mutation

No mutation

No mutationmutation

With and without mutation

Factors that will cause microevolution:

1. Mutation – nucleotide or chromosome change

2. Non random mating – mate selection

3. Gene Flow - migration

4. Genetic Drift – accidental loss of individuals

5. Natural Selection – most fit reproduce more often

Non random mating

The wolf is probably close to natural dog if dogs allowed to mate freely

Specific breeds of dog result if dogs are only allowed to breed with others in the same breed

Extreme example of nonrandom mating = inbreeding

Results in mostly homozygous genotypes (e.g. HH or hh)

Cubs low survival rate

Susceptible to disease

Males have low sperm count

Only chance for new genes is through mutation

20,000 Cheetahs

Factors that will cause microevolution:

1. Mutation – nucleotide or chromosome change

2. Non random mating – mate selection

3. Gene Flow - migration

4. Genetic Drift – accidental loss of individuals

5. Natural Selection – most fit reproduce more often

Gene flow (migration) Genes for the brown beetle move to green

populationPopulation A = 100% green Population B = 100% brown

Factors that will cause microevolution:

1. Mutation – nucleotide or chromosome change

2. Non random mating – mate selection

3. Gene Flow - migration

4. Genetic Drift – accidental loss of individuals

5. Natural Selection – most fit reproduce more often

Genetic Drift: accidental loss of members of a small population

20% purple

33% purple

33% purple

32% purple

Small population with 12.5% white and 87.5% dark

75% dark 25% white

100% dark 0% white

Factors that will cause microevolution:

1. Mutation – nucleotide or chromosome change

2. Non random mating – mate selection

3. Gene Flow - migration

4. Genetic Drift – accidental loss of individuals

5. Natural Selection – most fit reproduce more often

Bird eats dark moth Bird eats light moth

Light moth reproduces more often – why?

Dark moth reproduces more often – why?

Best adapted moth reproduces more offspring

Natural Selection does not give an organism an adaptation simply because it will do better with it.

– Adaptations occur by chance mutations

Factors that will cause microevolution:

1. Mutation – nucleotide or chromosome change

2. Non random mating – mate selection

3. Gene Flow - migration

4. Genetic Drift – accidental loss of individuals

5. Natural Selection – most fit reproduce more often

Review

SPECIES =

group of interbreeding populations reproductively isolated from other populations

Are lions and tigers separate species?

Liger = lion x tiger

Are horse and donkey different species??

Horse X Donkey = Mule (sterile)

sperm egg No meiosis

Ensatina eschscholtzii

Ensatina eschscholtzii

Geographic Isolation can lead to differences and

new species

Becomes separate species as mutations make them different

Kaibab and Abert’s squirrels separated by Grand Canyon =

geographic isolation

Colorado River

Geographic isolating mechanisms (fences) prevent exchange of genetic differences between

dog breeds allowing differences to build-up

If population is geographically isolated long enough, then behavioral

isolating mechanisms occur