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!!