EVOLUTION

Charles Darwin

Question for Thought

Earth has millions of other kinds Earth has millions of other kinds of organisms of everyof organisms of every

imaginable shape, size, and habitat. imaginable shape, size, and habitat. This variety of living things is This variety of living things is

called called biological biological diversitydiversity. How did all these . How did all these

different organisms arise?different organisms arise? How are they relatedHow are they related??

Darwin’s Theory of Evolution

Evolution, or change over time, is the , or change over time, is the process by which modern organisms have process by which modern organisms have descended from ancient organisms. descended from ancient organisms.

A scientific A scientific theory is a well-supported is a well-supported testable explanation of phenomena that testable explanation of phenomena that have occurred in the natural world.have occurred in the natural world.

How do you think Darwin came up with his theory?

Voyage of the Beagle

Voyage of Beagle

Dates: Dates: February 12th, 1831February 12th, 1831 Captain:Captain: Charles Darwin Charles Darwin ShipShip: H.M.S. Beagle: H.M.S. Beagle Destination:Destination: Voyage around the world. Voyage around the world. Findings:Findings: evidence to propose a evidence to propose a

revolutionary hypothesis about how life revolutionary hypothesis about how life changes over timechanges over time

Patterns of Diversity

Darwin visited Argentina and Australia which had Darwin visited Argentina and Australia which had similar grassland ecosystems. similar grassland ecosystems.

those grasslands were inhabited by very different those grasslands were inhabited by very different animals. animals.

neither Argentina nor Australia was home to the neither Argentina nor Australia was home to the sorts of animals that lived in European grasslands.sorts of animals that lived in European grasslands.

Living Organisms and Fossils

Darwin collected the preserved remains of Darwin collected the preserved remains of ancient organisms, called ancient organisms, called fossils. .

Some of those fossils resembled organisms that Some of those fossils resembled organisms that were still alive today.were still alive today.

Living Organisms and Fossils   Others looked completely unlike any creature he had Others looked completely unlike any creature he had

ever seen. ever seen.

As Darwin studied fossils, new questions arose. As Darwin studied fossils, new questions arose. Why had so many of these species disappeared? Why had so many of these species disappeared?

How were they related to living species?How were they related to living species?

Fossils

The Galapagos Island The smallest, lowest islands were hot, The smallest, lowest islands were hot,

dry, and nearly barren-Hood Island-sparse dry, and nearly barren-Hood Island-sparse vegetationvegetation

The higher islands had greater rainfall and The higher islands had greater rainfall and a different assortment of plants and a different assortment of plants and animals-Isabella- Island had rich animals-Isabella- Island had rich vegetationvegetation..

Animals found in the Galapagos

Land TortoisesLand Tortoises

Darwin FinchesDarwin Finches

Blue-Footed BoobyBlue-Footed Booby

Marine IguanasMarine Iguanas

The Journey Home

Darwin Observed that characteristics Darwin Observed that characteristics of many plants and animals vary of many plants and animals vary greatly among the islandsgreatly among the islands

HypothesisHypothesis:: Separate species may Separate species may have arose from an original ancestorhave arose from an original ancestor

Ideas that shaped Darwin’s Thinking James Hutton:James Hutton: 1795 Theory of 1795 Theory of

Geological changeGeological change Forces change Forces change

earth’s surface earth’s surface shapeshape

Changes are slowChanges are slow Earth much older Earth much older

than thousands of than thousands of yearsyears

Ideas that Shaped Darwin’s Thinking Charles LyellCharles Lyell Book: Book: Principles of Principles of

GeographyGeography Geographical features Geographical features

can be built up or torn can be built up or torn downdown

Darwin thought if Darwin thought if earth changed over earth changed over time, what about life?time, what about life?

Lamarck’s Theory of Evolution Tendency toward Perfection(Giraffe Tendency toward Perfection(Giraffe

necks)necks) Organisms Are Continually Changing Organisms Are Continually Changing

and Acquiring Features That Help Them and Acquiring Features That Help Them Live More Successfully In Their Live More Successfully In Their EnvironmentEnvironment

Use and Disuse (bird’s using forearms)Use and Disuse (bird’s using forearms)Acquired traits -> traits that developed over time by a species. Acquired traits -> traits that developed over time by a species.

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Lamarck’s Mistakes

Lamarck Did NOT Know how traits Lamarck Did NOT Know how traits were were inherited (Traits are passed inherited (Traits are passed through genes)through genes)

Genes Are NOT Changed By Genes Are NOT Changed By Activities In LifeActivities In Life

Change Through Change Through Mutation Occurs Mutation Occurs Before An Organism Is BornBefore An Organism Is Born

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Population Growth Thomas MalthusThomas Malthus--

19th century English 19th century English economisteconomist

If population grew If population grew (more Babies born (more Babies born than die)than die) Insufficient living Insufficient living

spacespace Food runs outFood runs out Darwin applied this Darwin applied this

theory to animalstheory to animals

Publication of Orgin of Species

Alfred Russel Wallace Alfred Russel Wallace wrote an essay wrote an essay summarizing summarizing evolutionary change evolutionary change from his field work in from his field work in MalaysiaMalaysia

Gave Darwin the drive Gave Darwin the drive to publish his findingsto publish his findings

Natural Selection & Artificial Selection Natural VariationNatural Variation--differences among --differences among

individuals of a speciesindividuals of a species Natural selection --is the gradual, non-random is the gradual, non-random

process by which biological traits become either process by which biological traits become either more or less common in a population as a function more or less common in a population as a function of differential reproduction of their bearers.of differential reproduction of their bearers.

Artificial selectionArtificial selection- nature provides the variation - nature provides the variation among different organisms, and humans select among different organisms, and humans select those variations they find useful.those variations they find useful.

Evolution by Natural Selection

The Struggle for ExistenceThe Struggle for Existence-members of -members of each species have to compete for food, each species have to compete for food, shelter, other life necessitiesshelter, other life necessities

Survival of the FittestSurvival of the Fittest-Some individuals -Some individuals better suited for the environmentbetter suited for the environment

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Survival of the Fittest

Fitness Ability of an Individual To Survive & Ability of an Individual To Survive &

ReproduceReproduce Adaptation

Inherited Characteristic That Increases Inherited Characteristic That Increases an Organisms Chance for Survival. an Organisms Chance for Survival. (can be physical or behavioral)(can be physical or behavioral)

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Struggle For Existence & Survival of The Fittest

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Survival of the Fittest

Key ConceptOver Time, Over Time, Natural Selection Natural Selection

Results In Changes In The Results In Changes In The Inherited Characteristics Of A Inherited Characteristics Of A Population. These Changes Population. These Changes Increase A Species Fitness In Its Increase A Species Fitness In Its EnvironmentEnvironment

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Descent Descent with ModificationDescent with Modification-Each living organism -Each living organism

has descended, with changes from other species has descended, with changes from other species over long periods of time. Ex) body structures, over long periods of time. Ex) body structures, niches, habitats.niches, habitats.

Common DescentCommon Descent- All species, living and extinct, - All species, living and extinct, were derived from common ancestorswere derived from common ancestors

Descent Divergent evolutionDivergent evolution: : is the process of two or more related is the process of two or more related

species becoming more and more dissimilar. species becoming more and more dissimilar. Ex) Adaptive radiation-When a single form of life Ex) Adaptive radiation-When a single form of life

successfully expands into many environments, the successfully expands into many environments, the process is termed "adaptive radiation." process is termed "adaptive radiation."

Convergent EvolutionConvergent Evolution: unrelated species : unrelated species become more and more similar in become more and more similar in appearance as they adapt to the same kind appearance as they adapt to the same kind of environmentof environment

Evidence of Evolution

The Fossil RecordThe Fossil Record

Geographic Distribution of Living ThingsGeographic Distribution of Living Things

Homologous Body StructuresHomologous Body Structures

Similarities in Early DevelopmentSimilarities in Early Development

Evidence for Evolution

The Fossil RecordThe Fossil Record--Layer show changeLayer show change

Geographic Geographic Distribution of Living Distribution of Living ThingsThings

Homologous Body Homologous Body StructuresStructures

Similarities in Early Similarities in Early DevelopmentDevelopment

Evidence of Evolution The Fossil RecordThe Fossil Record Geographic Geographic

Distribution of Distribution of Living ThingsLiving Things--similar similar environments have environments have similar types of similar types of organismsorganisms

Homologous Body Homologous Body StructuresStructures

Similarities in Early Similarities in Early DevelopmentDevelopment

Homologous Structures

Homologous StructuresHomologous Structures-structures that have -structures that have different mature forms in different organisms, but different mature forms in different organisms, but develop from the same develop from the same embryonic tissue.embryonic tissue.

Analogous Structures Structures of different species

having similar or corresponding function but not from the same evolutionary origin

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Evidence for Evolution - Comparative Embryology

(Similarities In Embryonic Development)

Embryo – early stages of vertebrate development

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Evidence for Evolution Not All Serve Important FunctionsNot All Serve Important Functions

Vestigial Organs: Vestigial Organs: organs that serve no organs that serve no useful function in an organismuseful function in an organismAppendix In ManAppendix In ManLegs On SkinksLegs On Skinks

Summary of Darwin’s Theory

Individuals in nature differ from one anotherIndividuals in nature differ from one another

Organisms in nature produce more offspring Organisms in nature produce more offspring than can survive, and many of those who do than can survive, and many of those who do not survive do not reproduce.not survive do not reproduce.

Because more organisms are produce than can Because more organisms are produce than can survive, each species must struggle for survive, each species must struggle for resourcesresources

Summary of Darwin’s Theory

Each organism is unique, each has advantages Each organism is unique, each has advantages and disadvantages in the struggle for existenceand disadvantages in the struggle for existence

Species change over timeSpecies change over time Individuals best suited for the environment survive Individuals best suited for the environment survive

and reproduce most successfuland reproduce most successful Species alive today descended with modification from Species alive today descended with modification from

species that lived in the pastspecies that lived in the past All organisms All organisms on earth are united into a single family on earth are united into a single family

tree of life by common descenttree of life by common descent