How Does Evolution How Does Evolution Happen? Happen?

(Natural Selection)

First man to explaino Charles DarwinCharles Darwin

o Took a five year voyage Took a five year voyage around the world after around the world after he got out of collegehe got out of college

o Served as a Served as a naturalistnaturalist on the British ship on the British ship HMS HMS BeagleBeagle

o Formed a theory of how Formed a theory of how evolutionevolution happened happened

o Collected plant and Collected plant and animal samples on his animal samples on his travelstravels

o Visited the Galapagos Visited the Galapagos islands just west of islands just west of EcuadorEcuador (South America) (South America)

Map of the Galapagos Islands

Galapagos Island Discoveries

o Found that the finches on Found that the finches on these islands were similar these islands were similar to Ecuador’s to Ecuador’s

o Each island was still a little Each island was still a little different from the nextdifferent from the next

o Found that theFound that the beaksbeaks of the of the finches had adapted to theirfinches had adapted to their foodfood source on the different source on the different islands.islands.

Finches

Darwin starts to think..o How did we get these similar species?How did we get these similar species?o He had ideas about the He had ideas about the EarthEarth

o He found that Earth has been formed by He found that Earth has been formed by naturalnatural processes over a long period of processes over a long period of timetime

o He had ideas about He had ideas about breedingbreedingo Selective breeding- breeding Selective breeding- breeding

plants/plants/animalsanimals to have desired to have desired characteristicscharacteristics

o He had ideas about He had ideas about populationspopulationso Realized that any species can produce Realized that any species can produce

many many offspringoffspring, but they are limited by , but they are limited by several factors.several factors.

What limits offspring?o StarvationStarvationo DiseaseDiseaseo CompetitionCompetitiono PredationPredation

o He found that really only a limited He found that really only a limited amount of individuals will survive to amount of individuals will survive to reproduce.reproduce.

o There is something unique about There is something unique about the survivors. They must have the survivors. They must have stronger geneticstronger genetic traitstraits. Those are . Those are the traits that will pass down to the traits that will pass down to their offspring.their offspring.

Darwin’s thinking lead to his theory of Natural Selection

o Once he returned from his voyage, Once he returned from his voyage, he thought forhe thought for 20 20 yrs about the yrs about the observations he had taken from the observations he had taken from the world and wrote aworld and wrote a bookbook called called On On the Origin of Species by Means of the Origin of Species by Means of Natural Selection.Natural Selection.

o Darwin’s theory of natural selectionDarwin’s theory of natural selection is is the process by which individuals best the process by which individuals best adapted to their environments survive adapted to their environments survive and reproduce more successfully than and reproduce more successfully than less well adapted individualsless well adapted individuals

o This theory of natural selection is This theory of natural selection is broken intobroken into fourfour parts.parts.

Four Parts of Natural Selectiono 1) 1) OverproductionOverproduction

oOrganisms will give birth to Organisms will give birth to thousands of offspring thousands of offspring realizing that some will realizing that some will become adults and others will become adults and others will not. not.

o 2) 2) Inherited VariationInherited VariationoEvery individual has its own Every individual has its own combo of traits. (similar tocombo of traits. (similar to parentsparents))

Continuedo 3) 3) Struggle to SurviveStruggle to Survive

oPredators, starvation, Predators, starvation, diseasesdiseases

o 4) 4) Successful ReproductionSuccessful ReproductionoThe organisms best The organisms best adaptedadapted in their in their environment will produce environment will produce the most surviving the most surviving offspring.offspring.

Think About it…

Darwin Lackedo When Darwin was introducing When Darwin was introducing

his his theorytheory of natural selection of natural selection he lacked two important he lacked two important things:things:o 1- He didn’t know how we inherit 1- He didn’t know how we inherit

traitstraitso 2- He didn’t know how the 2- He didn’t know how the

variationsvariations occurred occurred

o We have learned how both of We have learned how both of these occurrences happen, tell these occurrences happen, tell me how!me how!

Yes??o 1) We inherit traits from our 1) We inherit traits from our

parents when they get passed parents when they get passed down to the offspring.down to the offspring.

o 2) Variations occur because of 2) Variations occur because of the different the different genegene combinations that can be made combinations that can be made when the mother and father when the mother and father come together to produce come together to produce offspring.offspring.

Natural Selection in Actiono A population A population

changes inchanges in responseresponse to its environment.to its environment.

o Things that can Things that can affect an affect an environments environments population are:population are:o HuntingHuntingo ResistanceResistanceo CompetitionCompetition

Huntingo A new affect such as A new affect such as

hunting can play a role in hunting can play a role in how a population level how a population level risesrises or falls. or falls.

o In 1930 Uganda’s male In 1930 Uganda’s male elephant population that elephant population that contained tusks was 99% contained tusks was 99% and only 1% of them were and only 1% of them were born without them. Today born without them. Today 85% of male elephant 85% of male elephant population contains tusks.population contains tusks.

o Because of this, more of Because of this, more of the tusk less elephants are the tusk less elephants are surviving and reproducing. surviving and reproducing. This trait does get This trait does get passed passed downdown..

Resistanceo Some organisms such asSome organisms such as insectsinsects can can

build resistance to certain build resistance to certain chemicals.chemicals.

o This can send an increase in a This can send an increase in a particular insects population that particular insects population that could be harmfulcould be harmful..

o It doesn’t take long for insects to It doesn’t take long for insects to build up this resistance and build up this resistance and reproduce.reproduce.

o Generation timeGeneration time: the period : the period between thebetween the birthbirth of one generation of one generation and the birth of the next generation.and the birth of the next generation.

Competitiono Many species will Many species will

have competitions have competitions for theirfor their matesmates

o Some organisms Some organisms may over time may over time have somehave some interestinginteresting adaptations.adaptations.

o Feather colors, Feather colors, smells, dances, smells, dances, sounds, etc.sounds, etc.

Forming a New Specieso May form if the groups get May form if the groups get

separatedseparated from the original from the original population.population.

o The two groups can adapt to their The two groups can adapt to their environments and get to a point environments and get to a point where they are so where they are so differentdifferent they they can’t even mate anymore.can’t even mate anymore.

o A new species is a result of A new species is a result of evolutionevolution. We call this . We call this speciationspeciation..

o Separation-Adaptation-DivisionSeparation-Adaptation-Division