Introduction to Darwinian Evolution

Introduction toIntroduction toDarwinian EvolutionDarwinian Evolution

Chapter 18Chapter 18

Learning Objective 1Learning Objective 1

• What is What is evolutionevolution??

EvolutionEvolution

• Accumulation of inherited changes within a Accumulation of inherited changes within a populationpopulation over time over time

• Unifying concept of biologyUnifying concept of biology• links all fields of life sciences into a unified links all fields of life sciences into a unified

body of knowledgebody of knowledge

Learning Objective 2Learning Objective 2

• Discuss the historical development of the Discuss the historical development of the theory of evolutiontheory of evolution

Jean Baptiste de LamarckJean Baptiste de Lamarck

• Proposed that organismsProposed that organisms• change over time by natural phenomena, not change over time by natural phenomena, not

divine interventiondivine intervention• had vital force that changed them toward had vital force that changed them toward

greater complexity over timegreater complexity over time• could pass traits acquired during lifetime to could pass traits acquired during lifetime to

offspringoffspring

Charles DarwinCharles Darwin

• Theory of evolutionTheory of evolution• Based on observations during voyage of Based on observations during voyage of

HMSHMS BeagleBeagle

• Found similarities between organismsFound similarities between organisms• on arid Galápagos Islandson arid Galápagos Islands• on humid South American mainlandon humid South American mainland

Voyage of Voyage of HMS BeagleHMS Beagle

DarwinDarwin

• Influenced by Influenced by artificial selectionartificial selection• variety of domesticated plants and animalsvariety of domesticated plants and animals

• Applied Applied Thomas Malthus’sThomas Malthus’s ideas ideas • on human populations to natural populationson human populations to natural populations

• Influenced by geologists (Influenced by geologists (Charles LyellCharles Lyell))• idea that Earth was extremely oldidea that Earth was extremely old

Genetic VariationGenetic Variation

• Artificial selectionArtificial selection

• Natural VariationNatural Variation

KEY CONCEPTSKEY CONCEPTS

• Ideas about evolution originated long Ideas about evolution originated long before Darwin’s timebefore Darwin’s time

Learning Objective 3Learning Objective 3

• What are the What are the four premises of evolutionfour premises of evolution by by natural selection as proposed by Charles natural selection as proposed by Charles Darwin?Darwin?

4 Premises of Evolution4 Premises of Evolution by Natural Selection by Natural Selection

1. Genetic variation1. Genetic variation• exists among individuals in populationexists among individuals in population

2. Reproductive ability of each species2. Reproductive ability of each species• causes populations to geometrically causes populations to geometrically

increase over timeincrease over time

4 Premises of Evolution4 Premises of Evolution

3. Organisms compete with one another3. Organisms compete with one another• for resources: food, living space, water, lightfor resources: food, living space, water, light

4. Offspring with most favorable characteristics4. Offspring with most favorable characteristics• most likely to survive and reproducemost likely to survive and reproduce• pass genetic characteristics to next generationpass genetic characteristics to next generation

Natural SelectionNatural Selection

• Results in Results in adaptationsadaptations• evolutionary modificationsevolutionary modifications• improve chances of survival and reproductive improve chances of survival and reproductive

success in a particular environmentsuccess in a particular environment

• Over timeOver time• accumulated changes in geographically accumulated changes in geographically

separated populations produce new separated populations produce new speciesspecies

KEY CONCEPTSKEY CONCEPTS

• Darwin’s voyage on the Beagle provided Darwin’s voyage on the Beagle provided the basis for his theory of evolution by the basis for his theory of evolution by natural selectionnatural selection

Galapagos FinchesGalapagos Finches

Fig. 18-4a, p. 395

Fig. 18-4b, p. 395

Fig. 18-4c, p. 395

Animation: The Galapagos Animation: The Galapagos IslandsIslands

CLICKTO PLAY

KEY CONCEPTSKEY CONCEPTS

• Natural selection occurs because Natural selection occurs because individuals with traits that make them individuals with traits that make them better adapted to local conditions are more better adapted to local conditions are more likely to survive and produce offspring than likely to survive and produce offspring than are individuals that are not as well adaptedare individuals that are not as well adapted

Learning Objective 4Learning Objective 4

• What is the difference between the What is the difference between the modern synthesismodern synthesis and Darwin’s original and Darwin’s original theory of evolutiontheory of evolution??

Modern SynthesisModern Synthesis

• Or Or synthetic theory of evolutionsynthetic theory of evolution• combines Darwin’s theory of evolution by combines Darwin’s theory of evolution by

natural selection with modern geneticsnatural selection with modern genetics

• ExplainsExplains• why individuals in a population varywhy individuals in a population vary• how species adapt to their environmenthow species adapt to their environment

MutationMutation

• Provides Provides genetic variabilitygenetic variability• that that natural selectionnatural selection acts on during acts on during evolutionevolution

KEY CONCEPTSKEY CONCEPTS

• The modern synthesis combines Darwin’s The modern synthesis combines Darwin’s theory with geneticstheory with genetics

Learning Objective 5Learning Objective 5

• What evidence for evolution can be What evidence for evolution can be obtained from the obtained from the fossil recordfossil record? ?

Fossil RecordFossil Record

• FossilsFossils• remains or traces of ancient organismsremains or traces of ancient organisms• provide direct evidence of evolutionprovide direct evidence of evolution

Fossil RecordFossil Record

• Sedimentary rockSedimentary rock • layers occur in sequence of depositionlayers occur in sequence of deposition• recent layers on top of older onesrecent layers on top of older ones

• Index fossilsIndex fossils• characterize specific layer characterize specific layer

• RadioisotopesRadioisotopes• in rock accurately measure rock’s agein rock accurately measure rock’s age

Sedimentary RockSedimentary Rock

FossilsFossils

Whale Whale EvolutionEvolution

Fig. 18-8a, p. 399

Mesonychid

Fig. 18-8b, p. 399

Ambulocetus natans

Fig. 18-8c, p. 399

Rodhocetus

Fig. 18-8d, p. 399

Basilosaurus

Fig. 18-8e, p. 399

Balaenoptera

Radioisotope DecayRadioisotope Decay

Learning Objective 6Learning Objective 6

• What evidence for evolution is derived What evidence for evolution is derived from comparative anatomy?from comparative anatomy?

Homologous FeaturesHomologous Features

• Basic structural similaritiesBasic structural similarities• structures may be used in different waysstructures may be used in different ways

• Derived from same structureDerived from same structure• in common ancestorin common ancestor

• Indicate organism’s evolutionary affinities Indicate organism’s evolutionary affinities

Homology in AnimalsHomology in Animals

Fig. 18-10, p. 401

HUMANCAT WHALE BAT

Humerus

Ulna RadiusHumerus Carpal

5 RadiusMetacarpal Ulna

4 1 Carpal

RadiusUlna 1

5CarpalMetacarpal 1 3

Phalanges 4 21 2Phalanges 3

54 3

2

2345

Fig. 18-10, p. 401

HUMANCAT WHALE BAT

Humerus

HumerusRadius

Radius

Radius

5

4 1

15

1 3Phalanges 4 2

1 2Phalanges 3

54 3

2

2345

Metacarpal

Metacarpal

Ulna

Ulna

Ulna

Carpal

Carpal

Carpal

Stepped Art

Homology in PlantsHomology in Plants

Fig. 18-11a, p. 401

Spine

Fig. 18-11b, p. 401

Tendril

Leaflet

Leaf petiole

Stipule

Stem

Homoplastic FeaturesHomoplastic Features

• Evolved independentlyEvolved independently• similar functions in distantly related organismssimilar functions in distantly related organisms

• Demonstrate Demonstrate convergent evolutionconvergent evolution• organisms with separate ancestries adapt organisms with separate ancestries adapt

similarly to comparable environmentssimilarly to comparable environments

Fig. 18-12a, p. 402Aardvark (Orycteropus afer)

Fig. 18-12b, p. 402Giant anteater (Myrmecophaga tridactyla)

Fig. 18-12c, p. 402Pangolin (Manis crassicaudata)

HomoplasyHomoplasy

Fig. 18-13a, p. 403

Shoot (develops from axillary bud)

Spine (midrib of leaf) Leaf scar

A spine of Japanese barberry (Berberis thunbergii) is a modified leaf. (In this example, the spine is actually the midrib of the original leaf, which has been shed.)

Fig. 18-13b, p. 403

Thorn (develops from axillary bud)

Thorns of downy hawthorn (Crataegus mollis) are modified stems that develop from auxillary buds

Vestigial StructuresVestigial Structures

• Nonfunctional or degenerate remnantsNonfunctional or degenerate remnants• of structures functional in ancestral organismsof structures functional in ancestral organisms

• Structures occasionally become vestigialStructures occasionally become vestigial• as species adapt to different modes of lifeas species adapt to different modes of life

Vestigial StructuresVestigial Structures

Learning Objective 7Learning Objective 7

• What is What is biogeographybiogeography??

• How does distribution of organisms How does distribution of organisms support evolution?support evolution?

BiogeographyBiogeography

• Geographic distribution of organismsGeographic distribution of organisms• affects evolution affects evolution

• Areas separated from the rest of the world Areas separated from the rest of the world • contain organisms evolved in isolationcontain organisms evolved in isolation• unique to those areasunique to those areas

Continental DriftContinental Drift

• At one time, continents were joined to form At one time, continents were joined to form a supercontinenta supercontinent

• Continental driftContinental drift• caused landmasses to separatecaused landmasses to separate• played major role in evolutionplayed major role in evolution

Continental DriftContinental Drift

Fig. 18-15a, p. 404

Pangaea

Fig. 18-15b, p. 404

Laurasia

Gondwana

Fig. 18-15c, p. 404

N. America EuropeAsia

S. America

Africa

India

Australia

Antarctica

Fig. 18-15d, p. 404

N. America Eurasia

Africa

S.America

Australia

Antarctica

Fossil Fossil DistributionDistribution

Fig. 18-16, p. 405

(a) (b)Cynognathus Lystrosaurus

AfricaIndia

South America Australia

Antarctica

Mesosaurus(c)

Glossopteris (d)

Learning Objective 8Learning Objective 8

• How do How do developmental biologydevelopmental biology and and molecular biologymolecular biology provide insights into the provide insights into the evolutionary process?evolutionary process?

Evolutionary ChangesEvolutionary Changes

• Often result of gene mutations that affect Often result of gene mutations that affect events in development events in development

• Development in different animalsDevelopment in different animals• controlled by same kinds of genescontrolled by same kinds of genes• indicates shared evolutionary historyindicates shared evolutionary history

Genetic ChangesGenetic Changes

• Accumulation of genetic changesAccumulation of genetic changes• since organisms diverged since organisms diverged • modified development patterns in more modified development patterns in more

complex vertebrate embryoscomplex vertebrate embryos

Divergence in WhalesDivergence in Whales

Fig. 18-17, p. 407

Artiodactyls

Cam

el

Pig

Rum

inan

ts

(cow

, she

ep,

gira

ffe)

Hip

popo

tam

us

Cet

acea

ns

(wha

le, d

olph

in)

Common ancestor of hippos and whales

Common ancestor of artiodactyls and cetaceans

Molecular EvidenceMolecular Evidence for Evolution for Evolution

• UniversalUniversal genetic codegenetic code

• Conserved sequencesConserved sequences• of amino acids in proteinsof amino acids in proteins• of nucleotides in DNAof nucleotides in DNA

Molecular ClockMolecular Clock

Learning Objective 9Learning Objective 9

• How are evolutionary hypotheses tested How are evolutionary hypotheses tested experimentally?experimentally?

Reznick and EndlerReznick and Endler

• Studied effects of predation intensityStudied effects of predation intensity• on evolution of guppy populations in on evolution of guppy populations in

laboratory and naturelaboratory and nature

• Tested underlying processes of natural Tested underlying processes of natural selectionselection

Reznick ExperimentReznick Experiment

KEY CONCEPTSKEY CONCEPTS

• The evidence that evolution has taken The evidence that evolution has taken place and is still occurring is overwhelmingplace and is still occurring is overwhelming

Animation: Radiometric DatingAnimation: Radiometric Dating

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Animation: Morphological Animation: Morphological DivergenceDivergence

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Animation: Radioisotope DecayAnimation: Radioisotope Decay

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Video: Creation vs. EvolutionVideo: Creation vs. Evolution

• From ABC News, Environmental Science in the Headlines, 2005 DVD.From ABC News, Environmental Science in the Headlines, 2005 DVD.

CLICKTO PLAY

Video: Dinosaur DiscoveryVideo: Dinosaur Discovery

• From ABC News, Environmental Science in the Headlines, 2005 DVD.From ABC News, Environmental Science in the Headlines, 2005 DVD.