Chapter 17Chapter 17

Evidence of EvolutionEvidence of Evolution

ObjectivesObjectives

Be able to cite what biologist generally accept as Be able to cite what biologist generally accept as evidence that supports evolution.evidence that supports evolution.

Explain how fossils, comparative morphology, Explain how fossils, comparative morphology, patterns of development, and comparative patterns of development, and comparative biochemistry are used to reconstruct the past.biochemistry are used to reconstruct the past.

Explain Darwin’s views on evolutionExplain Darwin’s views on evolution Define natural selection.Define natural selection.

We have dated Asteroid impacts on Earth We have dated Asteroid impacts on Earth that correspond to mass extinctions that correspond to mass extinctions (dinosaurs)(dinosaurs)

Knowing what an asteroid impact will do to Knowing what an asteroid impact will do to us allows us to figure out how impacts us allows us to figure out how impacts affected life in the pastaffected life in the past

The rise of modern humans has been The rise of modern humans has been documented from numerous fossils.documented from numerous fossils.

17.0 : 17.0 : Measuring TimeMeasuring Time

17.1 Selective Breeding & 17.1 Selective Breeding & EvolutionEvolution

Evolution is genetic change in a line of Evolution is genetic change in a line of descent through successive descent through successive generationsgenerations

Selective breeding practices yield Selective breeding practices yield evidence that heritable changes do evidence that heritable changes do occuroccur

Evolutionary TheoriesEvolutionary Theories

Widely used to interpret the past and Widely used to interpret the past and present, and even to predict the present, and even to predict the futurefuture

Reveal connections between the Reveal connections between the geological record, fossil record, and geological record, fossil record, and organism diversityorganism diversity

Early Scientific TheoriesEarly Scientific Theories

Hippocrates - All aspects of nature can Hippocrates - All aspects of nature can be traced to their underlying causesbe traced to their underlying causes

Aristotle - Each organism is distinct Aristotle - Each organism is distinct from all the rest and nature is a from all the rest and nature is a continuum or organizationcontinuum or organization

Confounding EvidenceConfounding Evidence

BiogeographyBiogeography

Comparative anatomyComparative anatomy

Geologic discoveriesGeologic discoveries

BiogeographyBiogeography

Size of the known world expanded Size of the known world expanded

enormously in the 15th centuryenormously in the 15th century

Discovery of new organisms in previously Discovery of new organisms in previously

unknown places could not be explained unknown places could not be explained

by accepted beliefsby accepted beliefs How did species get from center of creation How did species get from center of creation

to all these places?to all these places?

Comparative MorphologyComparative Morphology

Study of similarities and differences in Study of similarities and differences in body plans of major groupsbody plans of major groups

Puzzling patterns:Puzzling patterns: Animals as different as whales and bats have Animals as different as whales and bats have

similar bones in forelimbs similar bones in forelimbs Some parts seem to have no function Some parts seem to have no function

Comparative AnatomyComparative Anatomy

Geological DiscoveriesGeological Discoveries

Similar rock layers throughout worldSimilar rock layers throughout world

Certain layers contain fossilsCertain layers contain fossils

Deeper layers contain simpler fossils than Deeper layers contain simpler fossils than

shallow layersshallow layers

Some fossils seem to be related to known Some fossils seem to be related to known

speciesspecies

17.2 19th Century - New 17.2 19th Century - New TheoriesTheories

Scientists attempt to reconcile evidence of Scientists attempt to reconcile evidence of change with traditional belief in a single change with traditional belief in a single creation eventcreation event

Two examplesTwo examples Georges Cuvier - multiple catastrophes, Georges Cuvier - multiple catastrophes,

leaving fewer speciesleaving fewer species Jean Lamarck - inheritance of acquired Jean Lamarck - inheritance of acquired

characteristics- the idea that simple forms had characteristics- the idea that simple forms had changed into more complex oneschanged into more complex ones

The Theory of UniformityThe Theory of Uniformity

Lyell’s Lyell’s Principles of GeologyPrinciples of Geology

He proposed the notion of gradual, He proposed the notion of gradual, Subtle, repetitive processes of change had Subtle, repetitive processes of change had shaped the Earthshaped the Earth

Challenged the view that Earth was only Challenged the view that Earth was only 6,000 years old.6,000 years old.

Darwin’s VoyageDarwin’s Voyage

At age 22, Charles Darwin began a five-At age 22, Charles Darwin began a five-year, round-the-world voyage aboard the year, round-the-world voyage aboard the BeagleBeagle

In his role as ship’s naturalist, he collected In his role as ship’s naturalist, he collected and examined the species that inhabited and examined the species that inhabited the regions the ship visitedthe regions the ship visited

Darwin’s VoyageDarwin’s Voyage

http://www.bing.com/videos/search?q=charles+darwin+hms+beagle+journey&mid=8E2162F5A654A4D74C9F8E2162F5A654A4D74C9F&view=detail&FORM=VIRE3

http://www.aboutdarwin.com/

17.3 Galapagos Finches17.3 Galapagos Finches

Darwin observed finches with a variety of Darwin observed finches with a variety of lifestyles and body formslifestyles and body forms

On his return, he learned that there were On his return, he learned that there were 13 species13 species

He attempted to correlate variations in He attempted to correlate variations in their traits with environmental challengestheir traits with environmental challenges

Malthus - Struggle to SurviveMalthus - Struggle to Survive

Thomas Malthus, a clergyman and Thomas Malthus, a clergyman and economist, wrote essay that Darwin economist, wrote essay that Darwin read on his return to Englandread on his return to England

Argued that as population size Argued that as population size increases, resources dwindle, the increases, resources dwindle, the struggle to live intensifies, and conflict struggle to live intensifies, and conflict increasesincreases

Darwin’s TheoryDarwin’s Theory

A population can change over time when A population can change over time when

individuals differ in one or more heritable individuals differ in one or more heritable

traits that are responsible for differences traits that are responsible for differences

in the ability to survive and reproduce.in the ability to survive and reproduce.

Natural SelectionNatural Selection

The major points of Darwin’s theory of The major points of Darwin’s theory of

natural selection were published in 1859.natural selection were published in 1859.

A difference in the survival and A difference in the survival and

reproductive success of different reproductive success of different

phenotypesphenotypes

Acts directly on phenotypes and indirectly Acts directly on phenotypes and indirectly

on genotypeson genotypes

Reproductive Capacity Reproductive Capacity & Competition& Competition

All populations have the capacity to All populations have the capacity to increase in numbersincrease in numbers

No population can increase No population can increase indefinitelyindefinitely

Eventually the individuals of a Eventually the individuals of a population will end up competing for population will end up competing for resourcesresources

Variation in PopulationsVariation in Populations

All individuals have the same genes that All individuals have the same genes that specify the same assortment of traitsspecify the same assortment of traits

Most genes occur in different forms Most genes occur in different forms (alleles) that produce different phenotypes(alleles) that produce different phenotypes

Some phenotypes compete better than Some phenotypes compete better than othersothers

Change over TimeChange over Time

Over time, the alleles that produce the Over time, the alleles that produce the most successful phenotypes will increase most successful phenotypes will increase in the populationin the population

Less successful alleles will become less Less successful alleles will become less commoncommon

Change leads to increased fitnessChange leads to increased fitness Increased adaptation to environmentIncreased adaptation to environment

Alfred WallaceAlfred Wallace

Naturalist who arrived at the same Naturalist who arrived at the same

conclusions Darwin didconclusions Darwin did

Wrote to Darwin describing his viewsWrote to Darwin describing his views

Prompted Darwin to finally present his Prompted Darwin to finally present his

ideas in a formal paper ideas in a formal paper

17.4 Fossils17.4 Fossils

Fossils are recognizable evidence of Fossils are recognizable evidence of ancient life ancient life

What do fossils tell us?What do fossils tell us? Each species is a mosaic of ancestral and Each species is a mosaic of ancestral and

novel traitsnovel traits All species that ever evolved are related to All species that ever evolved are related to

one another by way of descentone another by way of descent

StratificationStratification

Fossils are found in sedimentary rockFossils are found in sedimentary rock

This type of rock is formed in layersThis type of rock is formed in layers

In general, layers closest to the top In general, layers closest to the top

were formed most recentlywere formed most recently

Most fossils are skeletons, shells, Most fossils are skeletons, shells,

leaves, seeds, imprints of leaves.leaves, seeds, imprints of leaves.

Fossilization – slow processFossilization – slow process

Organism becomes Organism becomes buried in ash or buried in ash or sedimentssediments

Organic remains Organic remains become infused with become infused with metal and mineral ionsmetal and mineral ions

Fig.19.6, p. 309

Section 17.5: Radiometric DatingSection 17.5: Radiometric Dating Carbon 14 Dating – Radiometric DatingCarbon 14 Dating – Radiometric Dating

Because of the decay of the isotopes is Because of the decay of the isotopes is constant, the rate (half-life) can be constant, the rate (half-life) can be determined, and the time since its determined, and the time since its formation can be calculated back in time.formation can be calculated back in time.

See Geologic Time ScaleSee Geologic Time Scale

Record Is IncompleteRecord Is Incomplete

Fossils have been found for about Fossils have been found for about 250,000 species250,000 species

Most species weren’t preservedMost species weren’t preserved Record is biased toward the most Record is biased toward the most

accessible regionsaccessible regions

17.6 Drifting Continents17.6 Drifting Continents

Idea that the continents were once Idea that the continents were once joined and have since “drifted” apartjoined and have since “drifted” apart

Initially based on the shapes of Initially based on the shapes of changing land masses.changing land masses.

Wegener refined the hypothesis and Wegener refined the hypothesis and named the theoretical supercontinent named the theoretical supercontinent PangeaPangea

Evidence of MovementEvidence of Movement

Wegener cited evidence from glacial Wegener cited evidence from glacial deposits and fossilsdeposits and fossils

Magnetic orientations in ancient rocks do Magnetic orientations in ancient rocks do not align with the magnetic polesnot align with the magnetic poles

Discovery of seafloor spreading provided Discovery of seafloor spreading provided a possible mechanism a possible mechanism

Plate TectonicsPlate Tectonics

Earth’s crust Earth’s crust is fractured is fractured into platesinto plates

Movement of Movement of plates driven plates driven by upwelling by upwelling of molten rock of molten rock

Pacific

plate

Nazca

plate

North

American

plate

South

American

plate

Eurasian

plate

African

plate

Somali

plate

Pacific

plate

Indo-

Australian

plate

Antarctic plate

17.7 Comparative Morphology17.7 Comparative Morphology

Comparing body forms and structures of Comparing body forms and structures of

major lineagesmajor lineages

Guiding principle:Guiding principle: When it comes to introducing change in When it comes to introducing change in

morphology, evolution tends to follow the morphology, evolution tends to follow the

path of least resistancepath of least resistance

Morphological divergenceMorphological divergence

In morphological divergence, features In morphological divergence, features have departed in appearance and/or have departed in appearance and/or function from the ancestral form.function from the ancestral form.

These are body features that resemble These are body features that resemble one another in form due to descent one another in form due to descent through common ancestors.through common ancestors.

Ex. Similarity in bones in forelimbs.Ex. Similarity in bones in forelimbs.

Morphological ConvergenceMorphological Convergence

Morphological convergence is when Morphological convergence is when individuals of different lineages evolve individuals of different lineages evolve in similar ways under similar in similar ways under similar environmental pressuresenvironmental pressures

Produces analogous structures that Produces analogous structures that serve similar functionsserve similar functions

Comparative DevelopmentComparative Development

Each animal or plant proceeds through a Each animal or plant proceeds through a

series of changes in formseries of changes in form

Similarities in these stages may be clues Similarities in these stages may be clues

to evolutionary relationshipsto evolutionary relationships

Mutations that disrupt a key stage of Mutations that disrupt a key stage of

development are selected againstdevelopment are selected against

17.8 Altering Developmental 17.8 Altering Developmental ProgramsPrograms

Some mutations shift a step in a Some mutations shift a step in a

way that natural selection favorsway that natural selection favors

Small changes at key steps may Small changes at key steps may

bring about major differences bring about major differences

Insertion of transposons or gene Insertion of transposons or gene

mutations mutations

Similar Vertebrate EmbryosSimilar Vertebrate Embryos

Alterations that disrupted early development Alterations that disrupted early development have been selected againsthave been selected against

FISH REPTILE BIRD MAMMAL

Developmental ChangesDevelopmental Changes

Changes in the onset, rate, or time of Changes in the onset, rate, or time of

completion of development steps can completion of development steps can

cause allometric changescause allometric changes

Adult forms that retain juvenile featuresAdult forms that retain juvenile features

17.9 Comparative Biochemistry17.9 Comparative Biochemistry

Kinds and numbers of biochemical Kinds and numbers of biochemical traits that species share is a clue to traits that species share is a clue to how closely they are relatedhow closely they are related

We can compare DNA, RNA, or We can compare DNA, RNA, or proteinsproteins

More similarity means species are More similarity means species are more closely relatedmore closely related

Comparing ProteinsComparing Proteins

Compare amino acid sequence of proteins Compare amino acid sequence of proteins

produced by the same gene produced by the same gene

Human cytochrome Human cytochrome c c (a protein) (a protein) Identical amino acids in chimpanzee proteinIdentical amino acids in chimpanzee protein

Chicken protein differs by 18 amino acidsChicken protein differs by 18 amino acids

Yeast protein differs by 56Yeast protein differs by 56

Nucleic Acid ComparisonNucleic Acid Comparison

The degree of similarity of nucleotide The degree of similarity of nucleotide sequences of DNA reveals information sequences of DNA reveals information about evolutionary relationships.about evolutionary relationships.

Molecular ClockMolecular Clock

Assumption: “Ticks” (neutral mutations) Assumption: “Ticks” (neutral mutations) occur at a constant rate occur at a constant rate

These mutations accumulate in the These mutations accumulate in the DNA and can be used as a “molecular DNA and can be used as a “molecular clock” for dating times of divergence in clock” for dating times of divergence in species.species.

Review of evolutionReview of evolution

http://www.pbs.org/wgbh/evolution/