Evolution Evolution Natural SelectionNatural Selection

TheoryTheory

►What is a theory?What is a theory? A scientificA scientific theorytheory is a well-supported is a well-supported

testabletestable explanation of phenomena that explanation of phenomena that have occurred in the natural world.have occurred in the natural world.

►Theory of evolutionTheory of evolution EvolutionEvolution is the process by which modern is the process by which modern

organisms have descended from ancient organisms have descended from ancient organisms. Species has organisms. Species has changed over timechanged over time..

Charles DarwinCharles Darwin

Charles DarwinCharles Darwin Born Feb. 12, 1809Born Feb. 12, 1809 Joined Crew of HMS Joined Crew of HMS

Beagle, 1831Beagle, 1831 NaturalistNaturalist 5 Year Voyage 5 Year Voyage

around worldaround world Avid Collector of Avid Collector of

Flora & FaunaFlora & Fauna Astounded By Astounded By

Variety of LifeVariety of Life

Voyage of the Voyage of the BeagleBeagleIn 1831, Darwin set sail from England aboard the In 1831, Darwin set sail from England aboard the

H.M.S. H.M.S. BeagleBeagle for a voyage around the world. for a voyage around the world.

Darwin returned 5 years later in 1836Darwin returned 5 years later in 1836

ObservationsObservations

During his travels, Darwin made numerous During his travels, Darwin made numerous observationsobservations and collected evidence that and collected evidence that led him to propose a led him to propose a hypothesishypothesis about the about the way way lifelife changeschanges over time. over time.

► He observed many He observed many plantsplants and and animalsanimals were were well suited to the environments they well suited to the environments they inhabited.inhabited.

Darwin was puzzled by where different Darwin was puzzled by where different species lived and did not live.species lived and did not live.

Darwin's ObservationsDarwin's ObservationsLiving Organisms and Fossils Living Organisms and Fossils Darwin collected the Darwin collected the preservedpreserved remains of remains of

ancient organisms, called ancient organisms, called fossilsfossils. .

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

Others looked completely unlike any creature he Others looked completely unlike any creature he had ever seen.had ever seen.

Darwin's ObservationsDarwin's ObservationsThe The Galápagos IslandsGalápagos IslandsDarwin observed that the Galápagos Islands Darwin observed that the Galápagos Islands

were close together but had very different were close together but had very different climates.climates.

Copyright Pearson Prentice Hall

The Journey HomeThe Journey Home

Darwin observed that the Darwin observed that the characteristicscharacteristics of many animals and plants of many animals and plants variedvaried noticeably among the different islands of noticeably among the different islands of the Galápagos.the Galápagos.

Tortoises Tortoises

The Journey HomeThe Journey HomeDarwin wondered if animals living on Darwin wondered if animals living on different islands had once been different islands had once been members of the same members of the same speciesspecies. .

These separate species would have These separate species would have evolved from an original South evolved from an original South American American ancestorancestor species. species.

Those that helped Darwin’s Those that helped Darwin’s ideaidea

► HuttonHutton 1795 published 1795 published

theory about theory about geological forces geological forces that have shaped that have shaped Earth.Earth.

Layers of rock form Layers of rock form slowly.slowly.

Mountains formed Mountains formed from sea floorfrom sea floor

► LyellLyell Gave Darwin book Gave Darwin book

Principles of geologyPrinciples of geology Scientists must Scientists must

explain past events explain past events that have shaped the that have shaped the earth. earth.

Made Darwin think if Made Darwin think if the earth can change the earth can change over time what about over time what about life?life?

Hutton and Lyell both geologists (Earth millions of years old.

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Lamarck’s Theory of Evolution

►Idea called Law of Use and Disuse

►If a body part were used, it got stronger

►If body part NOT used, it deteriorated

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Lamarck’s Theory of Evolution

►Inheritance Of Acquired TraitsInheritance Of Acquired Traits Traits Acquired During Ones Lifetime Traits Acquired During Ones Lifetime

Would Be Passed To OffspringWould Be Passed To Offspring

Clipped ears of dogs could be passed to offspring!

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Lamarck’s Mistakes

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

►Genes Are NOT Changed By Activities In Life

►Change Through Mutation Occurs Before An Organism Is Born

Thomas MalthusThomas Malthus

► What was What was Malthus'Malthus' theory of theory of populationpopulation growth? growth? 1798 observed that babies were being 1798 observed that babies were being

born faster than people were dying.born faster than people were dying. Malthus reasoned that if the human Malthus reasoned that if the human

population continued to grow unchecked, population continued to grow unchecked, sooner or later there would be sooner or later there would be insufficientinsufficient living living spacespace and and foodfood for everyone. for everyone.

Publication of Publication of On the Origin On the Origin of Speciesof Species

► He shelved his manuscript for years He shelved his manuscript for years and told his wife to publish it in case and told his wife to publish it in case he died.he died.

► In 1858, Alfred In 1858, Alfred WallaceWallace sent an essay sent an essay to Darwin for review. Wallace’s ideas to Darwin for review. Wallace’s ideas summarized Darwin’s work.summarized Darwin’s work.

► In In 18591859, Darwin , Darwin publishedpublished his book, his book, On the Origin of SpeciesOn the Origin of Species..

In his book…In his book…

► Proposed a mechanism for evolution Proposed a mechanism for evolution called called natural selectionnatural selection. .

► Presented evidence that evolution has Presented evidence that evolution has been taking place for millions of yearsbeen taking place for millions of years—and continues in all living things.—and continues in all living things.

► Artificial selectionArtificial selection is the selection by is the selection by humans for breeding of useful traits humans for breeding of useful traits from the natural variation among from the natural variation among different organisms.different organisms.

The Struggle for Existence The Struggle for Existence 

► Darwin realized that high Darwin realized that high birthbirth ratesrates and a shortage of life's basic needs and a shortage of life's basic needs would force organisms to would force organisms to competecompete for for resourcesresources..

►How is natural selection related to a How is natural selection related to a species' fitness? species' fitness?

Survival of the Fittest Survival of the Fittest 

► The ability of an individual to survive and reproduce in its specific environment is fitness.

►Darwin proposed that fitness is the result of adaptations.

►An adaptation is any inherited characteristic that increases an organism's chance of survival.

Natural SelectionNatural Selection► Because of its similarities to artificial Because of its similarities to artificial

selection, Darwin referred to the survival selection, Darwin referred to the survival of the fittest as of the fittest as natural selectionnatural selection..

► In natural selection, the In natural selection, the traitstraits being being selected contribute to an organism's selected contribute to an organism's fitnessfitness in its in its environmentenvironment..

Natural SelectionNatural Selection

► Over time, natural selection results in Over time, natural selection results in changes in the inherited characteristics of a changes in the inherited characteristics of a population. These changes increase a population. These changes increase a species' fitness in its environment.species' fitness in its environment.

► NaturalNatural selection selection is the process by which is the process by which individuals that are better individuals that are better adaptedadapted to their to their environment are more likely to environment are more likely to survivesurvive and and reproduce than other members of the same reproduce than other members of the same speciesspecies.

►

Descent with ModificationDescent with Modification

► Natural selection produces organisms Natural selection produces organisms that have different structures, establish that have different structures, establish different niches, or occupy different different niches, or occupy different habitats. habitats.

► Each living species has Each living species has descendeddescended, , with changes, from other species over with changes, from other species over time. time.

► Darwin referred to this principle as Darwin referred to this principle as descent with modificationdescent with modification..

5 parts to natural selection

►Overproduction ►Competition ►Variations ►Adaptations ►Speciation

Overproduction

►Most species produce far more offspring than can possibly survive.

►Each year a female sea turtle lays over 100 eggs.

►Why isn’t the sea full of sea turtles?

Competition

►Since food and other resources are limited, the offspring must compete with each other to survive.

►Only a few turtles will survive long enough to reproduce.

VariationVariation

► Crossing-over increases the number of genotypes that can appear in offspring.

►Sexual reproduction produces different phenotypes, but it does not change the relative frequency of alleles in a population.

Adaptation► Some organisms are better adapted

to their environment.► Fitness – the ability of an individual to

survive and reproduce in its environment due its traits

► Survival in nature – live long enough to pass genes on to offspring.

►Traits that make organisms successful are passed to the next generation

Speciation

► a new species is created when enough time has passed

►over time, variations that make a species successful accumulate

►Eventually, the entire species is different than it was.

Evolution of a PopulationEvolution of a Population► A population is a group of individuals of

the same species that interbreed.► A gene pool consists of all genes, including

all the different alleles, that are present in a population.

►The relative frequency of an allele is the number of times the allele occurs in a gene pool, compared with the number of times other alleles for the same gene occur.

Genetic variation Genetic variation

► In genetic terms, evolution is any change in the relative frequency of alleles in a population.

► The two main sources of genetic variation are mutations and the genetic shuffling that results from sexual reproduction.

MutationMutation

►A mutation is any change in a sequence of DNA.

►Mutations occur because of mistakes in DNA replication or as a result of radiation or chemicals in the environment.

►Mutations do not always affect an organism’s phenotype.

Populations NOT individualsPopulations NOT individuals

► Natural selection affects which individuals survive and reproduce and which do not.

►Evolution is any change over time in the relative frequencies of alleles in a population.

►Populations, not individual organisms, can evolve over time.

Peppered Moth

►The Industrial Revolution began in England in the late 1700s.

►Smoke from the factories blackened the tree trunks of trees.

►Light colored moths were no longer camouflaged.

►What color was more suited for the new environment?

More on Speciation

►Speciation is the formation of new species.

►A species is a group of organisms that breed with one another and produce fertile offspring.

How do New Species Form?

►Geographic Isolation►Continental Drift►A new species may form when a

group of individuals remains separated from the rest of its species long enough to evolve different traits. A group is separated from the rest of the

species

Video

►Darwin

Evidence of EvolutionEvidence of Evolution

•1. The 1. The fossilfossil record record•2. Comparative 2. Comparative anatomyanatomy

•Homologous structuresHomologous structures

•3. Similarities in early 3. Similarities in early development, or development, or embryologyembryology..

Fossil RecordFossil Record►A fossil is the A fossil is the preservedpreserved remains or remains or tracestraces of of

an an organismorganism that lived in the past. that lived in the past.►A fossil can be formed from parts of live A fossil can be formed from parts of live

organisms, organisms, foot printsfoot prints, or burrows left in , or burrows left in mud.mud.

►Actual age of fossils is determined by Actual age of fossils is determined by radioactive datingradioactive dating

FossilsFossils

►Ice preservation►Tar pit►Tree sap hardens to

form amber.►Imprint fossils►Cast fossils►Mineralized fossils

video

►Fossil

► Most fossils are found in sedimentary rock – formed when water flows over land,

► Carrying the sediment (and whatever life form) into a body of water.

► Over time pressure turns the sediment into rock, preserving what’s inside.

Comparative Anatomy

►Similar body parts show an evolutionary relationship

►Homologous Body Structures – same bone structure but different functions.

► Vestigial Organs – organs or traces of organs that serve no purpose.

►Example: Humans: appendix, tailbone, wisdom teeth, and Goosebumps

Homologous Body Structures – same bone structure but different

functions.

Similarities in early Similarities in early development, or embryologydevelopment, or embryology

► The study of The study of embryosembryos and their and their developmentdevelopment

► The The similaritiessimilarities suggest an suggest an evolutionary evolutionary relationship among relationship among all all vertebratevertebrate species.species.

Speed of evolution2 theories

► Gradualism- Described as a slow ongoing process by which one species changes to a new species

► Punctuated Equilibrium- One species suddenly changes to another.

Graphs showing time frame of Graphs showing time frame of Evolution:Evolution:

►Gradualism: ► Punctuated Equilibrium

Time

#SPECIES

#SPECIES

Time

video

►clip

Relation and common descent

►All living organisms are related to one another.

►Common descent – all species – living and extinct – were derived from common ancestors.

►Humans did NOT evolve from apes.►We have a common ancestor that was

neither human nor ape.

► Common Ancestor: all living organisms have a common ancestor and all life can be traced back to one original cell.

► From there life become diverse► Common ancestor mean that living things can

be traced back to a common relative. ► Example: Humans did not evolve from Apes

but had a common ancestor with them 5 to 8 million years ago.

Branching Trees: CladogramsBranching Trees: Cladograms

►A A branchingbranching tree is a diagram that tree is a diagram that shows how scientists think different shows how scientists think different groups of organisms are groups of organisms are relatedrelated..

Practice questions► 1. A species of bird known as Bird of Paradise has been 1. A species of bird known as Bird of Paradise has been

observed in the jungles of New Guinea. The males shake observed in the jungles of New Guinea. The males shake their bodies and sometimes hang upside down to show off their bodies and sometimes hang upside down to show off their bright colors and long feathers to attract females. their bright colors and long feathers to attract females. Females usually mate with the “flashiest” males. These Females usually mate with the “flashiest” males. These observations can be used to support the concept thatobservations can be used to support the concept that

► (1) unusual courtship behaviors lead to extinction(1) unusual courtship behaviors lead to extinction► (2) some organisms are better adapted for asexual (2) some organisms are better adapted for asexual

reproductionreproduction► (3) homeostasis in an organism is influenced by physical (3) homeostasis in an organism is influenced by physical

characteristicscharacteristics► (4) behaviors that lead to reproductive success have (4) behaviors that lead to reproductive success have

evolvedevolved

► 2. Agriculturists have developed some varieties of 2. Agriculturists have developed some varieties of vegetables from common wild mustard plants, vegetables from common wild mustard plants, which reproduce sexually. Which statement best which reproduce sexually. Which statement best explains the development of these different explains the development of these different varieties of vegetables?varieties of vegetables?

► (1) Different varieties can develop from a single (1) Different varieties can develop from a single species as a result of the recombination of genetic species as a result of the recombination of genetic information.information.

► (2) Different species can develop from a single (2) Different species can develop from a single species as a result of the effect of similar species as a result of the effect of similar environmental conditions.environmental conditions.

► (3) Mutations will occur in the genes of a species (3) Mutations will occur in the genes of a species only if the environment changes.only if the environment changes.

► (4) Variations in a species will increase when the (4) Variations in a species will increase when the rate of mitosis is decreased.rate of mitosis is decreased.

►3. Even though identical twins have the 3. Even though identical twins have the same genetic material, they may develop same genetic material, they may develop slightly different characteristics becauseslightly different characteristics because

►(1) each twin receives different (1) each twin receives different chromosomes from the eggchromosomes from the egg

►(2) one twin may only have genes from (2) one twin may only have genes from the fatherthe father

►(3) gene expression may be influenced by (3) gene expression may be influenced by factors that switch genes on and offfactors that switch genes on and off

►(4) a gene mutation may have occurred (4) a gene mutation may have occurred before the zygote dividebefore the zygote divide

► 4. Which statement concerning the evolution of 4. Which statement concerning the evolution of species species AA, , BB, , CC, , DD, and , and E E is supported by the is supported by the diagram below?diagram below?

► (1) Species (1) Species B B and and C C can be found in today’s environments.can be found in today’s environments.► (2) Species (2) Species A A and and D D evolved from evolved from EE..► (3) Species (3) Species A A and and C C can still interbreed.can still interbreed.► (4) Species (4) Species AA, , BB, and , and E E all evolved from a common ancestor all evolved from a common ancestor

and all are successful today.and all are successful today.

►5. Young birds that have been raised in 5. Young birds that have been raised in isolation from members of their species isolation from members of their species build nests characteristic of their build nests characteristic of their species. This suggests that the nest-species. This suggests that the nest-building behavior isbuilding behavior is

►(1) genetically inherited from parents(1) genetically inherited from parents►(2) learned by watching members of (2) learned by watching members of

their speciestheir species►(3) a disadvantage to the survival of the (3) a disadvantage to the survival of the

speciesspecies►(4) a direct result of the type of food the (4) a direct result of the type of food the

bird eatsbird eats

►6. Which statement provides evidence that 6. Which statement provides evidence that evolution is still occurring at the present evolution is still occurring at the present time?time?

►(1) The extinction rate of species has (1) The extinction rate of species has decreased in the last 50 years.decreased in the last 50 years.

►(2) Many bird species and some butterfly (2) Many bird species and some butterfly species make annual migrations.species make annual migrations.

►(3) New varieties of plant species appear (3) New varieties of plant species appear more frequently in regions undergoing more frequently in regions undergoing climatic change.climatic change.

►(4) Through cloning, the genetic makeup of (4) Through cloning, the genetic makeup of organisms can be predicted.organisms can be predicted.

►7. When a species includes organisms 7. When a species includes organisms with a wide variety of traits, it is most with a wide variety of traits, it is most likely that this species will havelikely that this species will have

►(1) a high proportion of individuals (1) a high proportion of individuals immune to genetic diseasesimmune to genetic diseases

►(2) a greater chance to survive if (2) a greater chance to survive if environmental conditions suddenly environmental conditions suddenly changechange

►(3) less success competing for resources(3) less success competing for resources►(4) limitless supplies of important (4) limitless supplies of important

resources, such as food and waterresources, such as food and water

► 9. Some evolutionary pathways are represented in the diagram 9. Some evolutionary pathways are represented in the diagram below.below.

An inference that can be made from information in the diagram is An inference that can be made from information in the diagram is thatthat

► (1) many of the descendants of organism (1) many of the descendants of organism B B became extinctbecame extinct► (2) organism (2) organism B B was probably much larger than any of the other was probably much larger than any of the other

organisms representedorganisms represented► (3) most of the descendants of organism (3) most of the descendants of organism B B successfully adapted to successfully adapted to

their environmenttheir environment and have survived to the present timeand have survived to the present time