Theory of EvolutionTheory of Evolution

Chapter 15Chapter 15

15.1 Key Concepts15.1 Key Concepts

What was Charles Darwin’s What was Charles Darwin’s contribution of science?contribution of science?

What pattern did Darwin observe What pattern did Darwin observe among organisms of the Galapagos among organisms of the Galapagos Islands?Islands?

15-1 The Puzzle of Life’s 15-1 The Puzzle of Life’s DiversityDiversity

Biological diversity- variety of living Biological diversity- variety of living thingsthings How did they arise? Related?How did they arise? Related?

EvolutionEvolution- change over time; process by - change over time; process by which modern organisms have which modern organisms have descended from ancient organismsdescended from ancient organisms TheoryTheory- well-supported testable explanation - well-supported testable explanation

of phenomena that have occurred in the of phenomena that have occurred in the natural worldnatural world

Charles DarwinCharles Darwin

Charles Darwin (1809-1882)- Charles Darwin (1809-1882)- EnglishmanEnglishman Voyage aboard H.M.S. Beagle (1831)Voyage aboard H.M.S. Beagle (1831) During his travels, Darwin made During his travels, Darwin made

numerous observations and collected numerous observations and collected evidence that led him to propose a evidence that led him to propose a revolutionary hypothesis about the revolutionary hypothesis about the way life changes over timeway life changes over time

Collected plant and animal specimens Collected plant and animal specimens while ship was anchoredwhile ship was anchored

Darwin’s ObservationsDarwin’s Observations

Well suited for environmentWell suited for environment Many ways for survival and production of Many ways for survival and production of

offspringoffspring Puzzled by where species lived and did not Puzzled by where species lived and did not

livelive Gathered fossilsGathered fossils

Resembled organisms still aliveResembled organisms still alive Others looked completely differentOthers looked completely different

Galapagos Islands were very close together, Galapagos Islands were very close together, but had very different climatesbut had very different climates Tortoise shellsTortoise shells

Journey HomeJourney Home

Time spent thinkingTime spent thinking Darwin observed that the Darwin observed that the

characteristics of many animals and characteristics of many animals and plants varied noticeably among the plants varied noticeably among the different islands of the Galapagosdifferent islands of the Galapagos

15-2 Ideas That Shaped Darwin’s 15-2 Ideas That Shaped Darwin’s ThinkingThinking

Fossils caused Darwin to be skeptical Fossils caused Darwin to be skeptical of people’s viewsof people’s views Earth created only a few thousand years Earth created only a few thousand years

agoago Robin had always been a robinRobin had always been a robin

Discoveries challenged fundamental Discoveries challenged fundamental beliefs held at that timebeliefs held at that time

Lyell and HuttonLyell and Hutton

James HuttonJames Hutton Earth had to be much more than a few thousand years oldEarth had to be much more than a few thousand years old 1795, hypothesis about geological forces that have shaped 1795, hypothesis about geological forces that have shaped

EarthEarth Internal forces- mountains, valleys, rocks- affected by natural Internal forces- mountains, valleys, rocks- affected by natural

forces- rain, wind, heat and cold tempsforces- rain, wind, heat and cold temps Charles LyellCharles Lyell

Gave book to DarwinGave book to Darwin Processes that shaped the Earth millions of years earlier Processes that shaped the Earth millions of years earlier

continue in presentcontinue in present Fossils of marine animals above sea levelFossils of marine animals above sea level Influence?: If the Earth could change over time, might life Influence?: If the Earth could change over time, might life

change as well?change as well? It would have taken many, many years for life to change in It would have taken many, many years for life to change in

the way he suggested. This would have been possible only the way he suggested. This would have been possible only if the Earth were extremely oldif the Earth were extremely old

Jean- Baptiste Jean- Baptiste LamarckLamarck

Living things have changed over timeLiving things have changed over time 1809- hypothesis (11809- hypothesis (1stst to develop) to develop)

Tendency toward perfection- continually changing Tendency toward perfection- continually changing and acquiring features that help them live more and acquiring features that help them live more successfully in their environmentssuccessfully in their environments

Use and disuse- organisms could alter the size or Use and disuse- organisms could alter the size or shape of particular organs by using their bodies in shape of particular organs by using their bodies in new waysnew ways

Inheritance of acquire traits- pass on traits to Inheritance of acquire traits- pass on traits to offspringoffspring

Evaluation of hypothesisEvaluation of hypothesis Did not know how traits are inheritedDid not know how traits are inherited Did not know that behavior has no effect on Did not know that behavior has no effect on

heritanceheritance

Thomas MalthusThomas Malthus

1798- human population1798- human population Reasoned that if the human Reasoned that if the human

population continued to grow population continued to grow unchecked, sooner or later there unchecked, sooner or later there would be insufficient living space would be insufficient living space and food for everyoneand food for everyone

InfluenceInfluence What causes death of so many What causes death of so many

individuals?individuals? What factor/factors determine which What factor/factors determine which

ones survive and reproduce, and which ones survive and reproduce, and which do not?do not?

15-3 Darwin Presents His 15-3 Darwin Presents His CaseCase

1858- Alfred Wallace sent short 1858- Alfred Wallace sent short essay which contained thoughts on essay which contained thoughts on evolutionary changeevolutionary change

1859- Darwin publishes his book 1859- Darwin publishes his book On On the Origin of Speciesthe Origin of Species

Inherited Variation and Artificial Inherited Variation and Artificial SelectionSelection

Inherited variation- differences that are Inherited variation- differences that are passed from parents to offspringpassed from parents to offspring Larger fruits on plants; some cows give more Larger fruits on plants; some cows give more

milkmilk Today: caused by variations in their genesToday: caused by variations in their genes Then: revolutionary idea because variations thought Then: revolutionary idea because variations thought

to be minor defectsto be minor defects Artificial selection- selection by humans for Artificial selection- selection by humans for

breeding of useful traits from the natural breeding of useful traits from the natural variation among different organismsvariation among different organisms Animal breeders used heritable variation to Animal breeders used heritable variation to

improve livestock and cropsimprove livestock and crops

Evolution by Natural Evolution by Natural SelectionSelection

Malthus- high birth rates and shortage Malthus- high birth rates and shortage of life’s basic needs would eventually of life’s basic needs would eventually force organisms into a competition for force organisms into a competition for resourcesresources

Survival of the FittestSurvival of the Fittest Fitness- ability of an individual to survive Fitness- ability of an individual to survive

and reproduce in its specific environmentand reproduce in its specific environment Result of adaptation- any inherited Result of adaptation- any inherited

characteristic that increases an organism’s characteristic that increases an organism’s chance of survivalchance of survival

Can be anatomical (structural) or physiological Can be anatomical (structural) or physiological (functions)(functions)

Evolution by Natural Evolution by Natural SelectionSelection

Central to process of evolution by Central to process of evolution by natural selectionnatural selection

Individuals compete to survive and produce offspringIndividuals compete to survive and produce offspring Low levels of fitness = deathLow levels of fitness = death High levels of fitness = survivalHigh levels of fitness = survival

Survival of the fittest (natural selection)- Survival of the fittest (natural selection)- process by which individuals that are better process by which individuals that are better suited to their environment survive and suited to their environment survive and reproduce most successfully (takes place reproduce most successfully (takes place without human control or direction)without human control or direction) Can only be seen in time over successive Can only be seen in time over successive

generationsgenerations Only certain individuals of a population produce Only certain individuals of a population produce

new individualsnew individuals

Descent with ModificationDescent with Modification

Principle that each living species Principle that each living species descended with changes, from other descended with changes, from other species over time species over time Look different from ancestorsLook different from ancestors Implies that all living organisms are Implies that all living organisms are

related to one anotherrelated to one another Common descent- principle that all Common descent- principle that all

species were derived from common species were derived from common ancestorsancestors ““Tree of life” links all living thingsTree of life” links all living things

Evidence of EvolutionEvidence of Evolution Fossil RecordFossil Record

Fossils = record of history of EarthFossils = record of history of Earth Compare fossils of older rock layers and fossils Compare fossils of older rock layers and fossils

of younger rock layers told us that life on Earth of younger rock layers told us that life on Earth has changed over timehas changed over time

# of fossils has increased since Darwin, but we still # of fossils has increased since Darwin, but we still have gapshave gaps

Geographic DistributionGeographic Distribution Finches- similar but distinctly differentFinches- similar but distinctly different

Slightly different from mainland (S. America)Slightly different from mainland (S. America) Same ancestor with modificationsSame ancestor with modifications

Different species on continents of S. America Different species on continents of S. America and Australiaand Australia

Similar environments = similar features; different Similar environments = similar features; different ancestorsancestors

Evidence of EvolutionEvidence of Evolution

Homologous Body StructuresHomologous Body Structures Limbs vary greatly in form and function, yet Limbs vary greatly in form and function, yet

constructed from same basic bonesconstructed from same basic bones Homologous structures- structures that have Homologous structures- structures that have

different mature forms but develop from the different mature forms but develop from the same embryonic tissuesame embryonic tissue

Descent with modificationDescent with modification Group organisms to how recently they last Group organisms to how recently they last

shared a common ancestorshared a common ancestor Vestigial organVestigial organ- organ that serves no useful - organ that serves no useful

function in an organismfunction in an organism

EmbryologyEmbryology

Early stages, or embryos, of many Early stages, or embryos, of many animals with backbones are very animals with backbones are very similarsimilar

The same groups of embryonic cells The same groups of embryonic cells develop in the same order and in develop in the same order and in similar patterns to produce the similar patterns to produce the tissues and organs of all vertebratestissues and organs of all vertebrates

Summary of Darwin’s Summary of Darwin’s TheoryTheory

Individual organisms differ, and some Individual organisms differ, and some of this variation is heritableof this variation is heritable

Organisms produce more offspring Organisms produce more offspring than can survive, and many that do than can survive, and many that do survive do not reproducesurvive do not reproduce

Because more organisms are Because more organisms are produced than can survive, they produced than can survive, they compete for limited resourcescompete for limited resources