The proliferation of species:The proliferation of species:

Darwin and Mechanisms of Darwin and Mechanisms of EvolutionEvolution

The theory and why it worksThe theory and why it works

Causes of Evolution:Causes of Evolution:

Fossil Record: Fossil Record: Evidence of Evidence of EvolutionEvolution

• Indicates life began 3 byaIndicates life began 3 bya • Prokaryotes then Eukaryotes then Prokaryotes then Eukaryotes then

multicellular Eukaryotesmulticellular Eukaryotes

• Fossil record determines:Fossil record determines:• When species appearedWhen species appeared• The type of environmentThe type of environment• When/if species became extinctWhen/if species became extinct

Darwin: Brain Pop Video

What does the theory say?What does the theory say?

• Theory b/c lots of evidence but Theory b/c lots of evidence but not enough to make it a lawnot enough to make it a law

• States that:States that:

• Variations in individuals can Variations in individuals can lead to changes in whole lead to changes in whole speciesspecies

Natural Selection: The Idea Natural Selection: The Idea Behind the TheoryBehind the Theory• Evolution controlled by NATURAL Evolution controlled by NATURAL

processesprocesses• THE PROCESS IS:THE PROCESS IS:

LIVELIVE + + BREEDBREED

+ PASS ON GENETIC INFO+ PASS ON GENETIC INFO = = SURVIVAL OF SPECIESSURVIVAL OF SPECIES

• ““Survival of Fittest”Survival of Fittest”• Those Those best ADAPTEDbest ADAPTED will be able to will be able to DO THE DO THE

PROCESSPROCESS

Results of Natural SelectionResults of Natural Selection

• Short term result:Short term result:• Best fit (adapted) will pass on Best fit (adapted) will pass on GOODGOOD genes genes

to offspringto offspring

• Long term result:Long term result:• Change in Change in frequencyfrequency (number) of certain (number) of certain

traitstraits• Which do you think will increase in Which do you think will increase in

frequency GOOD OR BAD?frequency GOOD OR BAD?GOOD OF COURSE!GOOD OF COURSE!

• As more individuals have good trait, As more individuals have good trait, species is evolvingspecies is evolving

What drives evolution?What drives evolution?

Interactions between individuals and Interactions between individuals and the environment:the environment:

1.1. OVERPRODUCTIONOVERPRODUCTION

2.2. STRUGGLE FOR SURVIVALSTRUGGLE FOR SURVIVAL

3.3. GENETIC VARIATIONGENETIC VARIATION

4.4. SELECTION BY THE SELECTION BY THE ENVIRONMENTENVIRONMENT

Evolution Cause #1: Evolution Cause #1: OVERPRODUCTIONOVERPRODUCTION

• POTENTIAL TO PRODUCE MORE POTENTIAL TO PRODUCE MORE OFFSPRING THAN WILL SURVIVEOFFSPRING THAN WILL SURVIVE

• This means the best “fit” individuals This means the best “fit” individuals will survive, grow and reproduce.will survive, grow and reproduce.

• EX:EX: DEER, FISH DEER, FISH

Evolution Cause #2: Evolution Cause #2: STRUGGLE FOR SURVIVALSTRUGGLE FOR SURVIVAL

• Overproduction leads to STRUGGLE Overproduction leads to STRUGGLE within species:within species:

1.1. Only some live to reproduceOnly some live to reproduce

2.2. Competition for resourcesCompetition for resources

3.3. Best competitors will live and breedBest competitors will live and breed

• Must STRUGGLE with environment also Must STRUGGLE with environment also (disease, predators, temp changes etc)(disease, predators, temp changes etc)

• Those that withstand will survive!Those that withstand will survive!

Genetic importance and evidence Genetic importance and evidence of evolutionof evolution

Evolution Cause #3: Evolution Cause #3: GENETIC VARIATIONGENETIC VARIATION• Variation must exist within survivorsVariation must exist within survivors

• ExEx:: Longer legs, bigger claws, diff. fur Longer legs, bigger claws, diff. fur colorcolor

• Favored traits will stay in population Favored traits will stay in population and lead to evolutionand lead to evolution

• Adaptive Value:Adaptive Value:• Describes a trait that helps an individual Describes a trait that helps an individual

survive in a particular environmentsurvive in a particular environment• EXEX:: polar bears have black skin; the black polar bears have black skin; the black

skin has adaptive value b/c it helps them skin has adaptive value b/c it helps them survivesurvive

Evolution Cause #4: Evolution Cause #4: SELECTION SELECTION BY ENVIRONMENTBY ENVIRONMENT• Traits w/ adaptive value benefit those Traits w/ adaptive value benefit those

individualsindividuals

• If reproduce, offspring have traits tooIf reproduce, offspring have traits too

• Eventually, # of individuals with trait Eventually, # of individuals with trait increases, and most all will have it!increases, and most all will have it!

• Therefore, adapting to environment Therefore, adapting to environment DRIVES EVOLUTION!DRIVES EVOLUTION!

Evolutionary Trees: AnimalsEvolutionary Trees: Animals

Comparison of Human and Chimp Comparison of Human and Chimp ChromosomesChromosomes

Actual Cartoons from Scope’s Trial, 1925