Emergence of Evolutionary ThoughtEmergence of Evolutionary Thought

Evolution:Evolution: Change in populations of organisms over time Change in populations of organisms over time

Early Explanation of life’s diversityEarly Explanation of life’s diversitySpecies individually created at one time and one placeSpecies individually created at one time and one place

Questions arising from such thoughtsQuestions arising from such thoughtsWhy were organisms different in different regions of earth?Why were organisms different in different regions of earth?Why are current organisms different from ancient organisms?Why are current organisms different from ancient organisms?If each species is different, why are there the same fundamental If each species is different, why are there the same fundamental structures (bone plans) that do different things in animals?structures (bone plans) that do different things in animals?

New IdeasNew IdeasScientists thought that species changed over timeScientists thought that species changed over time

Both animals, though very different, Both animals, though very different, exhibit similar wing structuresexhibit similar wing structures

Extinction, fossil record, and Carbon-14 dating Extinction, fossil record, and Carbon-14 dating suggest that organisms arose (and became suggest that organisms arose (and became

extinct) at different time periods extinct) at different time periods

Chimps- Arose on earth ~6 million years ago

Dinosaurs- Arise ~ 200 mya- Dinosaurs- Arise ~ 200 mya-

Extinct 65 myaExtinct 65 mya

Woolly Mammoth- Extinct Woolly Mammoth- Extinct 4500 years ago4500 years ago

Different regions of planet have animals Different regions of planet have animals with unique traits that help them survivewith unique traits that help them survive

New IdeasNew Ideas

Scientists thought that species changed over timeScientists thought that species changed over time

Lamarck’s Disproven Theory of EvolutionLamarck’s Disproven Theory of Evolution

Jean Baptiste LamarckJean Baptiste Lamarck

Believed that an animal’s physical Believed that an animal’s physical

needs determine its development and genesneeds determine its development and genes

Exp. GiraffeExp. Giraffe

Early Giraffes stretched their necks to feedEarly Giraffes stretched their necks to feed

Long neck was then passed off to offspringLong neck was then passed off to offspring

WRONG!!!WRONG!!!

Charles Darwin 1809-1882Charles Darwin 1809-1882Putting the Picture TogetherPutting the Picture Together

Darwin Travels to the Galapagos IslandsDarwin Travels to the Galapagos Islands

Witnessed tremendous diversity of animal lifeWitnessed tremendous diversity of animal life

Fascinated by differences among beaks on finchesFascinated by differences among beaks on finches

Becomes convinced that species change over timeBecomes convinced that species change over time

Young bull

Old bull

Thomas Malthus & Charles DarwinThomas Malthus & Charles Darwin

Malthus Malthus

Populations tend to grow faster than the Populations tend to grow faster than the food supply needed to feed itfood supply needed to feed it

Charles Lyell & Charles DarwinCharles Lyell & Charles Darwin

LyellLyell

Changes occur over time in geology; land Changes occur over time in geology; land formations move and topography changesformations move and topography changes

Darwn’s Descent with ModificationDarwn’s Descent with ModificationEvolutionary pathway resembled a branched treeEvolutionary pathway resembled a branched tree

NOT a ladder from lower forms to higher formsNOT a ladder from lower forms to higher forms

No species that exists today was an ancestor to another living speciesNo species that exists today was an ancestor to another living species

Darwin’s ObservationsDarwin’s Observations•Individuals in a population vary, some of these variations are Individuals in a population vary, some of these variations are inheritableinheritable•Populations produce more offspring than the environment’s food, Populations produce more offspring than the environment’s food, space, and other assets.space, and other assets.•Therefore, species compete for resourcesTherefore, species compete for resources

Lions and cheetahs compete for foodLions and cheetahs compete for food

Dolphins compete for baitfishDolphins compete for baitfish

The Mechanism of Natural SelectionThe Mechanism of Natural SelectionNatural Selection Natural Selection greater reproductive success displayed by greater reproductive success displayed by individuals with favorable traitsindividuals with favorable traits

Nature selects that are passed on to the next generationNature selects that are passed on to the next generation

VariationVariation differences within a population differences within a population

AdaptationsAdaptations traits that are selected for because they help an traits that are selected for because they help an organism survive and reproduceorganism survive and reproduce

Evolution occurs when genes in a population change shift to enhance Evolution occurs when genes in a population change shift to enhance survival and reproductionsurvival and reproduction

Exp. GiraffeExp. Giraffe

How Do Variations Arise?How Do Variations Arise?•Natural selection IS NOT the cause of variationNatural selection IS NOT the cause of variation

•Mutation-> Random changes in DNA sequences in the parents genomeMutation-> Random changes in DNA sequences in the parents genome

•Gene ShufflingGene Shuffling mixing of parental chromosomes can create new mixing of parental chromosomes can create new genetic combinationsgenetic combinations

•Variation arises randomly. Variations are then selected on by nature. Variation arises randomly. Variations are then selected on by nature.

•Variations which are selected for are called adaptationsVariations which are selected for are called adaptations

Adaptations and SpeciationAdaptations and SpeciationTypes of Adaptations Types of Adaptations

Structural Adaptations Structural Adaptations Involve structure or anatomy Involve structure or anatomy

Bird’s beak, Anteaters sticky tongueBird’s beak, Anteaters sticky tongue

Physiological Adaptations Physiological Adaptations Functions in organisms Functions in organisms

Poison Venom in a snake, ink of an octopusPoison Venom in a snake, ink of an octopus

Behavioral Adaptations Behavioral Adaptations Behavior aids in survival and reproduction Behavior aids in survival and reproduction

Wildabeasts/ Caribou/ Bird MigrationWildabeasts/ Caribou/ Bird Migration

Wolves Hunt in Packs Wolves Hunt in Packs

Fish swim in schoolsFish swim in schools

Types of AdaptationsTypes of Adaptations

StructuralStructural

PhysiologicalPhysiological

Wolf PackWolf Pack

Herd of African GazellesHerd of African Gazelles

Species & SpeciationSpecies & SpeciationSpecies Species group of organisms that can interbreed and produce fertile group of organisms that can interbreed and produce fertile offspringoffspring

Horses + Donkey = Mule…Not the same species Horses + Donkey = Mule…Not the same species

Human male + human female = human baby…same species!Human male + human female = human baby…same species!

HorseHorse DonkeyDonkey MuleMule

Speciation Speciation Organisms which are separated by distance + gene pool Organisms which are separated by distance + gene pool will no longer interbreed. Each group becomes new specieswill no longer interbreed. Each group becomes new species

Types of Natural SelectionTypes of Natural Selection

Directional Selection Directional Selection shifts a population toward one extreme form of shifts a population toward one extreme form of a traita trait

Example: 4 million years ago; heavy cheetahsExample: 4 million years ago; heavy cheetahs

Over time, light, fast animals reproduced more successfullyOver time, light, fast animals reproduced more successfully

Natural selection favored the genes that pushed the cheetah’s weight in Natural selection favored the genes that pushed the cheetah’s weight in one direction…lighterone direction…lighter

Types of Natural SelectionTypes of Natural SelectionStabilizing SelectionStabilizing Selection shifts a population toward intermediate shifts a population toward intermediate (medium) traits(medium) traits

Example: Most human babies weight ~ 7poundsExample: Most human babies weight ~ 7pounds

Disruptive Selection Disruptive Selection Extreme phenotypes are more common Extreme phenotypes are more common

Example: African butterflies appear as either bright orange or bright Example: African butterflies appear as either bright orange or bright blueblue

These colors mimic other butterflies that are foul-tasting; less likely to These colors mimic other butterflies that are foul-tasting; less likely to be eatenbe eaten

Intermediate butterflies look like neither, and are more likely to be eatenIntermediate butterflies look like neither, and are more likely to be eaten

Patterns of EvolutionPatterns of EvolutionSpecies become dissimilar or more alike over timeSpecies become dissimilar or more alike over time

Gradual Change Gradual Change Genetic changes occur slowly over many Genetic changes occur slowly over many generationsgenerations

Divergent Evolution Divergent Evolution Single population is split into 2 or more Single population is split into 2 or more populations.populations.

Exp. Ground squirrels in the Grand Canyon were split into 2 Exp. Ground squirrels in the Grand Canyon were split into 2 populations after canyon widenedpopulations after canyon widened

Patterns of EvolutionPatterns of Evolution

Adaptive Radiation Adaptive Radiation Organisms occupy different niches in an Organisms occupy different niches in an environment and diverge from one anotherenvironment and diverge from one another

Exp. Darwin’s FinchesExp. Darwin’s Finches

Convergent Evolution Convergent Evolution 2 dissimilar species evolve in ways to make 2 dissimilar species evolve in ways to make them LOOK more similarthem LOOK more similar

Exp. Sugar GlidersExp. Sugar Gliders winged marsupials in Australia winged marsupials in Australia

Flying Squirrels Flying Squirrels Winged squirrels in Northern Hemisphere Winged squirrels in Northern Hemisphere

Sugar GliderSugar Glider Flying SquirrelFlying Squirrel

Pace of EvolutionPace of EvolutionGradualism Gradualism Over time, new species arise as environment change Over time, new species arise as environment change

If true, we should see intermediate species in fossil record…not always If true, we should see intermediate species in fossil record…not always truetrue

Punctuated Equilibrium Punctuated Equilibrium Species exist for long periods of time Species exist for long periods of time without changes, then large changes occur over short periods of timewithout changes, then large changes occur over short periods of time

Populations & Evolution• Larger populations tend to have more genetic variation• Smaller populations tend to have less genetic variation• Genetic Drift/Founder Effect Loss of genetic variation

due small population sizes. Extinction more likely• 10,000 years ago, almost all cheetahs go extinct due to

climate changes. Resulting cheetahs have little genetic diversity

Evidence for EvolutionEvidence for EvolutionFossil Fossil trail of animal that is preserved in rock trail of animal that is preserved in rock

Found in Sedimentary RockFound in Sedimentary Rock

Fossils show overall structural scheme of how living things evolvedFossils show overall structural scheme of how living things evolved

Body schemeBody scheme

Feeding behaviorFeeding behavior

MobilityMobility

Society?Society?

New fossils in upper layers, older fossils in lower layersNew fossils in upper layers, older fossils in lower layers

ExamplesExamplesBurgess ShaleBurgess Shale

Location : British Columbia, CanadaLocation : British Columbia, Canada

Development: Foot of continental shelfDevelopment: Foot of continental shelf

Organisms: Early Marine worms (Hallucigenia)Organisms: Early Marine worms (Hallucigenia)

Badlands, SDBadlands, SD

Development: Shallow oceanDevelopment: Shallow ocean

Organisms: Early Squid, octopusOrganisms: Early Squid, octopus

BadlandsBadlands

ImportanceImportanceLand masses moveLand masses move

Were once covered under oceanic waterWere once covered under oceanic water

Species adapt and go extinct Species adapt and go extinct

Comparative AnatomyComparative AnatomyHomologous structuresHomologous structures Similar structures in related organisms Similar structures in related organisms

Suggests that organism arose from a common ancestorSuggests that organism arose from a common ancestor

Exp. Cheetah forelimb = human handExp. Cheetah forelimb = human hand

Wing = Whale flipperWing = Whale flipper

Vestigial OrgansVestigial OrgansOrgans with no apparent use, but resemble functional structures in Organs with no apparent use, but resemble functional structures in ancestorsancestors

Whale PelvisWhale Pelvis

Whale femurWhale femur

Wisdom TeethWisdom Teeth

AppendixAppendix

Comparative EmbryologyComparative EmbryologyOrganisms with common descent have similar organsOrganisms with common descent have similar organs

Vertebrates breathe though lungsVertebrates breathe though lungs

As embryos, vertebrates have gills (turns into Eustachian tube)As embryos, vertebrates have gills (turns into Eustachian tube)

BiochemistryBiochemistryCommon ancestors have similar fundamental body chemistryCommon ancestors have similar fundamental body chemistry

Most organisms have:Most organisms have:

Same 4 bases in DNASame 4 bases in DNA

Same 20 AASame 20 AA

BiogeographyBiogeographyStudy of species distribution on Galapagos Islands look similar to Study of species distribution on Galapagos Islands look similar to South American speciesSouth American species

Each island would have to had it own special creation event for each Each island would have to had it own special creation event for each species; more likely migrated from South Americaspecies; more likely migrated from South America

Direct EvidenceDirect EvidenceBacteria & AntibioticsBacteria & Antibiotics

Fruit Flies (Drosophila)Fruit Flies (Drosophila)

Artificial SelectionArtificial selection (or selective breeding) describes intentional breeding for certain traits, or combination of traits

Dogs are a prime example.

Bulldogs selectively bred for increasingly large heads. Most bulldogs delivered via Caesarian Section. Trait not favored in nature, but selected for by humans