EvolutionEvolution

BiologyBiology

What is evolution?What is evolution? Process by which Process by which

organisms pass on organisms pass on traits from generation to traits from generation to generationgeneration

Over large stretches of Over large stretches of time time

Explains the origin of Explains the origin of new species and new species and diversity diversity

The living species of The living species of today are related to today are related to each other through each other through common traitscommon traits

Charles DarwinCharles Darwin

Theory of Natural Theory of Natural SelectionSelection– Species that are Species that are better better

adaptedadapted to their to their environment will environment will live live longer and reproducelonger and reproduce creating more offspring creating more offspring like them like them

– ““Survival of the fittestSurvival of the fittest””

How did Darwin form his How did Darwin form his theory?theory?

1831: naturalist on 1831: naturalist on the H.M.S. the H.M.S. BeagleBeagle for a for a 5 year voyage 5 year voyage around the worldaround the world

Galapagos IslandsGalapagos Islands– FinchesFinches

13 species of finches13 species of finches Beak size and shape Beak size and shape

varied, most likely varied, most likely due to their island due to their island locations and locations and available foodavailable food

Finches had adapted Finches had adapted to best obtain food to best obtain food in their environmentin their environment

Darwin’s FinchesDarwin’s Finches

MicroevolutionMicroevolution Any evolutionary Any evolutionary

change below the level change below the level of speciesof species

Small changesSmall changes in in within alleles of a within alleles of a population or species population or species

Effects the phenotype Effects the phenotype of organisms that of organisms that make up that make up that population or species. population or species.

Leads to natural Leads to natural selectionselection– Peppered mothsPeppered moths– Antibiotic resistanceAntibiotic resistance

MacroevolutionMacroevolution Change at or above Change at or above

the level of speciesthe level of species Speciation: Speciation:

– the splitting of a the splitting of a speciesspecies into two into two

– the change of a the change of a species over time into species over time into anotheranother

History of life using History of life using all available all available evidence: geology, evidence: geology, fossils, and fossils, and morphology of living morphology of living organisms. organisms.

Micro vs. MacroMicro vs. Macro

Micro vs. MacroMicro vs. Macro

MUTATIONS CAUSE MUTATIONS CAUSE VARIATION!VARIATION!

Natural selection happens Natural selection happens because of:because of:

MutationsMutationsVariationVariationEnvironmental influenceEnvironmental influence

Let’s look at an exampleLet’s look at an example

Example:Example:In the U.S., where people In the U.S., where people

use shampoos with use shampoos with particular chemicals in particular chemicals in

order to kill lice, we have a order to kill lice, we have a lot of lice that are lot of lice that are

resistant to the chemicals resistant to the chemicals in those shampoos.in those shampoos.

Resistant means unaffectedResistant means unaffected

Hypothesis AHypothesis A: Exposure to : Exposure to lice shampoo actually caused lice shampoo actually caused mutations for resistance to mutations for resistance to

the shampoo.the shampoo.

Hypothesis B: Hypothesis B: Resistant Resistant strains of lice were always strains of lice were always there—and are just more there—and are just more

frequent now because all the frequent now because all the non-resistant lice died a non-resistant lice died a

sudsy death.sudsy death.

Which of these hypotheses is Which of these hypotheses is correct?correct?

Hypothesis BHypothesis BWhy?Why?

Variation is there alreadyVariation is there alreadyShampoo killed the “weaker” liceShampoo killed the “weaker” liceOther lice live and reproduce to Other lice live and reproduce to

make more resistant licemake more resistant lice

MUTATION ARE NOT CAUSED!MUTATION ARE NOT CAUSED!

Lamarck was an evolutionist who Lamarck was an evolutionist who believed in hypothesis A. believed in hypothesis A.

He was proven wrong. He was proven wrong.

He called his theory “Acquired He called his theory “Acquired Characteristics”. Characteristics”.

DARWINDARWINHypothesis B is what Darwin Hypothesis B is what Darwin

discovered. discovered. He called these mutations or He called these mutations or

changes ADAPTATIONSchanges ADAPTATIONS

• AcquiredAcquired characteristicharacteristics passed cs passed down to down to offspringoffspring

• Essentially Essentially saying that saying that because because something something was to be was to be beneficial in beneficial in a given a given environmentenvironment, then an , then an organism organism could “pass could “pass that trait” to that trait” to its offspringits offspring

Variation, Variation, natural natural selection & selection & heredityheredity

Random Random mutations mutations brought about brought about changes in changes in traitstraits

If that change If that change was better was better suited to an suited to an environment, environment, that organism that organism had a better had a better chance of chance of survivalsurvival

What EVOLUTION is NOT!!What EVOLUTION is NOT!!