Chapter 15 Chapter 15 EvolutionEvolution
15.1 Darwin15.1 Darwin’s Theory of Natural Selection’s Theory of Natural Selection
15.2 Evidence of Evolution15.2 Evidence of Evolution
15.3 Shaping Evolutionary Theory15.3 Shaping Evolutionary Theory
15.1 Darwin15.1 Darwin’s Theory of Natural Selection’s Theory of Natural Selection
Main idea: Main idea: Charles Darwin developed a theory of Charles Darwin developed a theory of evolution based on natural selectionevolution based on natural selection
ObjectivesObjectives Discuss the evidence that convinced Darwin Discuss the evidence that convinced Darwin
that species could change over time.that species could change over time. List the four principles of natural selection.List the four principles of natural selection. Show how natural selection could change a Show how natural selection could change a
populationpopulation
New VocabularyNew Vocabulary Selective breeding, Artificial selection, Natural Selective breeding, Artificial selection, Natural
selection, Evolutionselection, Evolution
Charles DarwinCharles Darwin boarded boarded the HMS Beaglethe HMS Beagle in in 18311831..Most believed the world Most believed the world was about was about 6,0006,000 years old. years old.During the shipDuring the ship’s five year ’s five year voyage, Darwin made voyage, Darwin made extensive collections of extensive collections of rocks, rocks, fossilsfossils, plants and , plants and animals.animals.
He also read Charles LyellHe also read Charles Lyell’s ’s Principles of Principles of Geology Geology – a book proposing the Earth – a book proposing the Earth was was millionsmillions of years old. of years old.
Developing the Theory of Developing the Theory of Natural SelectionNatural Selection
In 1835, the Beagle arrived in the In 1835, the Beagle arrived in the Galapagos Islands off the coast of South Galapagos Islands off the coast of South America.America.Darwin began to collect mockingbirds, Darwin began to collect mockingbirds, finches, and other animals on the finches, and other animals on the fourfour islands. islands. He noticed that the He noticed that the differentdifferent islandsislands seemed to have their own, slightly seemed to have their own, slightly differentdifferent varieties varieties of animals.of animals.
Developing the Theory of Developing the Theory of Natural SelectionNatural Selection
HMS BeagleHMS Beagle
Almost every Almost every specimen specimen that Darwin that Darwin had collected had collected on the islands on the islands was new to was new to European European scientists. scientists.
Darwin suspected populations from the mainland Darwin suspected populations from the mainland changedchanged after reaching the Galápagos. after reaching the Galápagos.
Galápagos IslandsGalápagos Islands
Developing the Theory of Developing the Theory of Natural SelectionNatural Selection
Darwin hypothesized that Darwin hypothesized that newnew species species could appear could appear graduallygradually through small through small changeschanges in ancestral species. in ancestral species.
Darwin inferred that if humans could Darwin inferred that if humans could change species by change species by artificial selectionartificial selection (selective breeding), then perhaps the (selective breeding), then perhaps the same process could work in same process could work in naturenature..
Developing the Theory of Developing the Theory of Natural SelectionNatural Selection
Darwin called his theory Darwin called his theory Natural SelectionNatural Selection
Developing the Theory of Developing the Theory of Natural SelectionNatural Selection
Natural SelectionNatural Selection
He reasoned that, He reasoned that, given enough time, given enough time, natural selection could natural selection could modifymodify a population a population enough to produce a enough to produce a new species.new species.
Darwin published Darwin published On the Origin of SpeciesOn the Origin of Species by Means of Natural Selection by Means of Natural Selection in 1859.in 1859.
Today, biologists use the term evolution to Today, biologists use the term evolution to define define changeschanges in groups of organisms in groups of organisms through through time.time.
DarwinDarwin’s theory of natural selection is ’s theory of natural selection is NOT NOT the same as evolution. Natural the same as evolution. Natural selection is a means of explaining selection is a means of explaining HOW HOW evolutionevolution works.works.
The Origin of SpeciesThe Origin of Species
15.2 Evidence of Evolution15.2 Evidence of EvolutionMain idea: Main idea: Multiple lines of evidence support the Multiple lines of evidence support the theory of evolution.theory of evolution.Objectives: Objectives: Describe how fossils provide evidence of Describe how fossils provide evidence of
evolution.evolution. Discuss morphological evidence of evolution.Discuss morphological evidence of evolution. Explain how physiology and biochemistry Explain how physiology and biochemistry
provide evidence of evolution.provide evidence of evolution.New VocabularyNew Vocabulary Derived traitDerived trait Ancestral traitAncestral trait Homologous structureHomologous structure Vestigial structureVestigial structure Analogous structureAnalogous structure
EmbryoEmbryo FitnessFitness MimicryMimicry CamouflageCamouflage
Support for EvolutionSupport for Evolution
The theory of The theory of evolutionevolution states that all states that all organisms on Earth have descended from a organisms on Earth have descended from a common ancestorcommon ancestor..
The The fossil recordfossil record offers some of the most offers some of the most significant evidence of evolutionary change.significant evidence of evolutionary change. Fossils provide a Fossils provide a recordrecord of species that of species that
lived long ago.lived long ago. Fossils show that ancient species share Fossils show that ancient species share
similarities similarities with species that now live on with species that now live on Earth.Earth.
The giant armadillo-like The giant armadillo-like glyptodont, glyptodont, Glyptodon,Glyptodon,is is an an extinctextinct animal that animal that Darwin thought must be Darwin thought must be related to the related to the livingliving armadillos of today.armadillos of today.The The fossil recordfossil record provides provides information for information for determining the ancestry determining the ancestry of organisms and the of organisms and the patternspatterns of evolution. of evolution.
Support for EvolutionSupport for EvolutionThe Fossil RecordThe Fossil Record
Two major classes of traits:Two major classes of traits:Derived traits are Derived traits are newly evolved newly evolved
features, such as feathers, that do not features, such as feathers, that do not appear in the fossils of common appear in the fossils of common ancestors.ancestors.
Ancestral traits Ancestral traits are more are more primitive primitive featuresfeatures, such as teeth and tails, that , such as teeth and tails, that do appear in ancestral forms.do appear in ancestral forms.
Support for EvolutionSupport for EvolutionThe Fossil RecordThe Fossil Record
Transitional fossils provide detailed Transitional fossils provide detailed patternspatterns of evolutionary change for of evolutionary change for ancestors of many modern animals, ancestors of many modern animals, including mollusks, horses, whales and including mollusks, horses, whales and humans.humans.
Example:Example: ArcheopteryxArcheopteryx
Shares features of Shares features of bothboth dinosaurs dinosaurs and birds.and birds.
Support for EvolutionSupport for EvolutionThe Fossil RecordThe Fossil Record
Homologous Homologous structures are structures are anatomically anatomically similarsimilar structures structures inheritedinherited from a from a common common ancestor.ancestor.The forelimbs of The forelimbs of vertebrates are vertebrates are adapted for adapted for different uses, different uses, but they all have but they all have similar bones.similar bones.
Similar Similar structure; structure; differentdifferent functionfunction..
Support for EvolutionSupport for EvolutionComparative AnatomyComparative Anatomy
Vestigial structures are Vestigial structures are the the reducedreduced forms of forms of functional structures in functional structures in other organisms.other organisms.Evolutionary theory Evolutionary theory predicts that features predicts that features of ancestors that no of ancestors that no longer have a function longer have a function for that species will for that species will become become smallersmaller over over time until they are time until they are lostlost..
Examples: Snake pelvis, Examples: Snake pelvis, human human appendix,appendix, blind blind fish and salamanders that fish and salamanders that live in caves but have live in caves but have eyes.eyes.
Support for EvolutionSupport for EvolutionComparative AnatomyComparative Anatomy
Analogous structures can be Analogous structures can be used for the used for the same purpose same purpose and can be and can be similarsimilar in in construction, but are construction, but are notnot inheritedinherited from a common from a common ancestor.ancestor.Show that functionally similar Show that functionally similar features can evolve features can evolve independentlyindependently in similar in similar environments.environments.DifferentDifferent structure; structure; samesame function; function;
Support for EvolutionSupport for EvolutionComparative AnatomyComparative Anatomy
Analogous structures example:Analogous structures example: Human eye and squid eyeHuman eye and squid eye
SimilaritiesSimilarities The iris to regulate light entering the lensThe iris to regulate light entering the lens Each eye is filled with fluidEach eye is filled with fluid Both eyes use a lens to focusBoth eyes use a lens to focus
function; function;
Support for EvolutionSupport for EvolutionComparative AnatomyComparative Anatomy
An An embryoembryo is an early pre-birth stage of an is an early pre-birth stage of an organismorganism’s development.’s development.
Vertebrate Vertebrate embryos exhibit embryos exhibit homologous homologous structuresstructures during certain during certain phases of phases of development development but become but become totally different totally different structures in structures in the adult forms.the adult forms.
Support for EvolutionSupport for EvolutionComparative EmbryologyComparative Embryology
Comparative BiochemistryComparative Biochemistry
Common ancestry Common ancestry can be seen in the can be seen in the complex complex metabolic metabolic moleculesmolecules that that many different many different organisms organisms shareshare..
Support for EvolutionSupport for Evolution
The genomes of humans and chimpanzees The genomes of humans and chimpanzees differ by only about 1% of their genetic makeupdiffer by only about 1% of their genetic makeup
Geographic DistributionGeographic Distribution
The The distributiondistribution of plants and animals that of plants and animals that Darwin saw during his travels first Darwin saw during his travels first suggested evolution to Darwin.suggested evolution to Darwin.
Rabbit in EuropeRabbit in Europe Mara in S. AmericaMara in S. America
Support for EvolutionSupport for Evolution
Scientists have Scientists have confirmed and confirmed and expanded Darwinexpanded Darwin’s ’s study of the distribution study of the distribution of plants and animals of plants and animals around the world in a around the world in a field of study now called field of study now called biogeography.biogeography.
Evolution is intimately linked with Evolution is intimately linked with climateclimate and and geological geological forcesforces..
Geographic DistributionGeographic DistributionSupport for EvolutionSupport for Evolution
AdaptationAdaptation
An An adaptationadaptation is a trait is a trait shaped by natural shaped by natural selection that selection that increasesincreases an organisman organism’s ’s reproductive success.reproductive success.
FitnessFitness is a measure of the relative is a measure of the relative contribution an individual trait makes to the contribution an individual trait makes to the next generation. It is often measured as the next generation. It is often measured as the number of number of reproductivelyreproductively viable offspring that viable offspring that an organism produces in the next generation.an organism produces in the next generation.
Camouflage allows Camouflage allows organisms to become organisms to become almost almost invisibleinvisible to to predators. Some species predators. Some species have evolved morphological have evolved morphological adaptations that allow them adaptations that allow them to blend in with their to blend in with their environments.environments.
MimicryMimicry is another is another morphological adaptation morphological adaptation that allows one species to that allows one species to evolve to evolve to resembleresemble another speciesanother species..
AdaptationAdaptationTypes of AdaptationTypes of Adaptation
Can you see the peppered moth?Can you see the peppered moth?
AdaptationAdaptationTypes of AdaptationTypes of Adaptation
When disturbed, When disturbed, this octopus flashes this octopus flashes and intensifies its and intensifies its stripes, resembling stripes, resembling a poisonous sea a poisonous sea snake. Unlike the snake. Unlike the sea snake, the sea snake, the octopus venom is octopus venom is harmlessharmless
AdaptationAdaptationTypes of AdaptationTypes of Adaptation
Antimicrobial Antimicrobial resistanceresistance - An - An antibiotic is a antibiotic is a medicine that slows medicine that slows or kills the growth of or kills the growth of bacteria.bacteria. Some bacteria Some bacteria
have evolved a have evolved a resistanceresistance to to certain antibiotics.certain antibiotics.
People infected with resistant bacteria can People infected with resistant bacteria can never never get rid of get rid of it.it.
AdaptationAdaptationTypes of AdaptationTypes of Adaptation
15.3 Shaping Evolutionary Theory15.3 Shaping Evolutionary Theory
Main idea: Main idea: The theory of evolution continues to The theory of evolution continues to be refined as scientists learn new information.be refined as scientists learn new information.
Objectives:Objectives: Discuss patterns observed in evolution.Discuss patterns observed in evolution. Describe factors that influence speciation.Describe factors that influence speciation. Compare gradualism with punctuated equilibrium.Compare gradualism with punctuated equilibrium.
Review VocabularyReview Vocabulary Allele: alternative forms of a character trait that can Allele: alternative forms of a character trait that can
be inherited.be inherited.
15.3 Shaping Evolutionary Theory15.3 Shaping Evolutionary Theory
Hardy-Weinberg PrincipleHardy-Weinberg Principle
Genetic driftGenetic drift
Founder effectFounder effect
BottleneckBottleneck
Punctuated EquilibriumPunctuated Equilibrium
Sexual selectionSexual selection
New Vocabulary
Mechanisms of EvolutionMechanisms of Evolution
Darwin’s theory of natural selection Darwin’s theory of natural selection remainsremains the central theme of the central theme of evolutionevolutionScientists of today know that natural Scientists of today know that natural selection is not the only mechanism selection is not the only mechanism of evolutionof evolutionEvolution occurs at the Evolution occurs at the populationpopulation level, with genes as the level, with genes as the raw material.raw material.
Mechanisms of EvolutionMechanisms of Evolution
Hardy-Weinberg Principle states that when Hardy-Weinberg Principle states that when allelic frequencies remain constant, a population allelic frequencies remain constant, a population is in genetic is in genetic equilibriumequilibrium..
Population GeneticsPopulation Genetics
Even though the number of owls doubled, the Even though the number of owls doubled, the ratioratio of of gray to red owls remained the gray to red owls remained the same.same.
pp2 2 + 2pq + q+ 2pq + q2 2 = 1= 1
This equation allows us to determine the This equation allows us to determine the equilibriumequilibrium frequency of each frequency of each genotypegenotype in in the population: the population:
homozygoushomozygous dominant (p dominant (p22))
heterozygousheterozygous (2pq) (2pq)
homozygoushomozygous recessive (q recessive (q22))Note the sum of these frequencies equals Note the sum of these frequencies equals one.one.
Mechanisms of EvolutionMechanisms of EvolutionPopulation GeneticsPopulation Genetics
A population in genetic equilibrium must meet all A population in genetic equilibrium must meet all fivefive conditions conditions
1.1.The population is very The population is very largelarge
2.2.No No immigration immigration or or emigrationemigration
3.3.Mating is Mating is randomrandom
4.4.MutationsMutations do not occur (no new variations) do not occur (no new variations)
5.5.Natural selectionNatural selection does not occur does not occur
Population GeneticsPopulation Genetics
Mechanisms of EvolutionMechanisms of Evolution
Genetic Drift is a change in the allelic Genetic Drift is a change in the allelic frequencies in a population that is due to frequencies in a population that is due to chancechance..In In smallersmaller populations, the effects of populations, the effects of genetic drift becomes more genetic drift becomes more pronouncedpronounced, , and the chance of losing an allele and the chance of losing an allele becomes greater.becomes greater.Examples: Founder Effect & BottleneckExamples: Founder Effect & Bottleneck
Mechanisms of EvolutionMechanisms of EvolutionGenetic DriftGenetic Drift
Founder Effect Founder Effect occurs when a small occurs when a small sample of a population settles in a location sample of a population settles in a location separatedseparated from the rest of the from the rest of the populationpopulation
Genetic DriftGenetic Drift
Alleles that were Alleles that were uncommonuncommon in the in the original population original population might be might be commoncommon in the new in the new population.population.
Mechanisms of EvolutionMechanisms of Evolution
Bottleneck occurs Bottleneck occurs when a population when a population declinesdeclines to a very to a very low number and low number and then then reboundsrebounds
Mechanisms of EvolutionMechanisms of EvolutionGenetic DriftGenetic Drift
Can Can decrease decrease genetic genetic variety.variety.
A population in genetic equilibrium A population in genetic equilibrium experiences no experiences no gene flowgene flow,, however, few however, few populations are populations are isolatedisolated
RandomRandom movement of individuals between movement of individuals between populations populations reducesreduces differences between differences between populationspopulations
Mechanisms of EvolutionMechanisms of EvolutionGene FlowGene Flow
RarelyRarely is mating is mating completely random in a completely random in a population.population.Usually individuals mate Usually individuals mate with individuals in close with individuals in close proximityproximity..
Nonrandom matingNonrandom mating
Mechanisms of EvolutionMechanisms of Evolution
This promotes inbreeding and could lead to a This promotes inbreeding and could lead to a change in allelic proportions favoring individuals change in allelic proportions favoring individuals that are that are homozygoushomozygous for particular traits. for particular traits.
A mutation is a A mutation is a random random changechange in genetic in genetic material.material.Occasionally mutations Occasionally mutations provide an provide an advantageadvantage to to organisms and become organisms and become more common in more common in subsequent generations.subsequent generations.Basis upon which Basis upon which natural natural selectionselection works. works.
Mechanisms of EvolutionMechanisms of EvolutionMutationMutation
Select the individuals that are Select the individuals that are best adapted for best adapted for survivalsurvival and and reproductionreproduction
StabilizingStabilizing selection selection eliminate extreme eliminate extreme
expressionsexpressionsBirth WeightsBirth Weights
DirectionalDirectional selection selection makes organisms more fit.makes organisms more fit.
Peppered MothsPeppered MothsDisruptiveDisruptive selection selection
process that splits a process that splits a population into two groups. population into two groups.
Lake Erie Water Lake Erie Water SnakesSnakes
Mechanisms of EvolutionMechanisms of EvolutionNatural SelectionNatural Selection
Sexual selectionSexual selection operates in operates in populations where males and populations where males and females differ significantly in females differ significantly in appearanceappearance.. MalesMales are largest and most are largest and most
colorful in the groupcolorful in the group More likely target for More likely target for predatorspredators
yet bodies enhance reproductive yet bodies enhance reproductive successsuccess
Examples: Peacocks & DeerExamples: Peacocks & Deer
Natural SelectionNatural Selection
Mechanisms of EvolutionMechanisms of Evolution
preventsprevents reproduction reproduction by making fertilization by making fertilization unlikely.unlikely. Eastern and Western Eastern and Western
meadowlarks similar meadowlarks similar in appearance but in appearance but their mating songs their mating songs separate them separate them behaviorally.behaviorally.
Reproductive IsolationReproductive IsolationPrezygotic IsolationPrezygotic Isolation
Occurs when Occurs when fertilization has fertilization has occurredoccurred but a but a hybrid offspring hybrid offspring cannot develop cannot develop or reproduce.or reproduce.
Reproductive IsolationReproductive IsolationPostzygotic IsolationPostzygotic Isolation
A Liger is the offspring of a male lion A Liger is the offspring of a male lion and a female tiger. Ligers are and a female tiger. Ligers are sterile.sterile.
A A physicalphysical barrier divides one population barrier divides one population into two or more populations.into two or more populations.
SpeciationSpeciation
Allopatric speciationAllopatric speciation
For speciation to occur, a population must For speciation to occur, a population must divergediverge and then be reproductively and then be reproductively isolatedisolated..
Species evolves into a new species Species evolves into a new species withoutwithout a physical barrier a physical barrier
SpeciationSpeciation
Sympatric speciationSympatric speciation
Apple maggot flies Apple maggot flies lay eggs on apples or lay eggs on apples or hawthorns depending hawthorns depending on the type of fruit on the type of fruit the grew up on.the grew up on.
For speciation to occur, a population must For speciation to occur, a population must diverge and then be reproductively isolated.diverge and then be reproductively isolated.
Can occur in a relatively Can occur in a relatively shortshort time when one time when one species gives rise to species gives rise to manymany different species different species in response to the creation of new in response to the creation of new habitathabitat or or some other ecological opportunity.some other ecological opportunity.
Patterns of EvolutionPatterns of EvolutionAdaptive Radiation (aka divergent evolution)Adaptive Radiation (aka divergent evolution)
Follows Follows large-scale large-scale extinctionextinction eventsevents Cichlid fish Cichlid fish
of Lake of Lake Victoria in Victoria in Africa.Africa.
The relationship between two species might be The relationship between two species might be so close that the evolution of one species so close that the evolution of one species affects affects the evolutionthe evolution of the other species. of the other species.
MutualismMutualism – occurs when two species benefit – occurs when two species benefit each other.each other.
CoevolutionCoevolution
Patterns of EvolutionPatterns of Evolution
The plant evolves a The plant evolves a chemical defensechemical defense
The insects evolve the The insects evolve the biochemistry to biochemistry to resistresist the the defensedefense
Response continues to escalate.Response continues to escalate.
Patterns of EvolutionPatterns of EvolutionCoevolutionCoevolutionCoevolutionary arms race – one species can Coevolutionary arms race – one species can
evolve a parasitic evolve a parasitic dependencydependency on another on another species.species.
A plant and an insect that is dependent on A plant and an insect that is dependent on the plant for foodthe plant for food
UnrelatedUnrelated species species evolve similar traits evolve similar traits even though they live even though they live in in differentdifferent parts of parts of the world.the world.
Occurs in Occurs in environments that are environments that are geographically far geographically far apart but have similar apart but have similar ecologyecology and and climate.climate.
Patterns of EvolutionPatterns of EvolutionConvergent EvolutionConvergent Evolution
Punctuated Punctuated equilibrium equilibrium explains explains rapidrapid spurts of genetic spurts of genetic change causing change causing species to species to diverge diverge quicklyquickly..
Rate of SpeciationRate of Speciation
Patterns of EvolutionPatterns of Evolution
Evolution proceeds in Evolution proceeds in smallsmall, , gradualgradual steps = steps = gradualism.gradualism.