Chapter 5: Changes over TimeChapter 5: Changes over TimeSection 1: Darwin’s TheorySection 1: Darwin’s TheoryWho was Charles Darwin?Who was Charles Darwin?

A A naturalistnaturalist (a (a person who person who studies the natural studies the natural world)world)

His observations of His observations of plants and animals plants and animals led him to develop led him to develop the theory of the theory of evolutionevolution by by naturalnatural selectionselection

Darwin observed many species during his voyage on Darwin observed many species during his voyage on the HMS Beagle, what is a species?the HMS Beagle, what is a species?

A A groupgroup of of similar similar organisms that organisms that can can matemate with with each other and each other and produce produce fertilefertile offspringoffspring

What did Darwin notice on the What did Darwin notice on the Galapagos Islands? Galapagos Islands?

Many of the plants Many of the plants and animals on the and animals on the Galapagos were Galapagos were similar to similar to organismsorganisms on mainland South on mainland South America America

However, there were However, there were also important also important differencesdifferences between between the organisms on the the organisms on the islandsislands and those on and those on the mainlandthe mainland

What did Darwin conclude led to What did Darwin conclude led to the differences between species?the differences between species?

After studying the After studying the different different finchesfinches on on the Galapagos the Galapagos Islands Darwin Islands Darwin concluded that their concluded that their different different beakbeak shape was due to shape was due to an an adaptationadaptation

Adaptation – A Adaptation – A traittrait that helps an that helps an organism survive organism survive and and reproducereproduce

What did Darwin start to believe was What did Darwin start to believe was occurring amongst the different occurring amongst the different

species?species?

Darwin thought the Darwin thought the species gradually species gradually changedchanged over over many generations many generations and became better and became better adaptedadapted to the to the new conditionsnew conditions

EvolutionEvolution – the – the gradual change in a gradual change in a species over timespecies over time

Why was Darwin’s idea Why was Darwin’s idea considered a scientific theory?considered a scientific theory?

It was a well-tested It was a well-tested conceptconcept that explains a that explains a wide range of wide range of observationsobservations

Darwin and Alfred Russell eventually Darwin and Alfred Russell eventually proposed an explanation for how proposed an explanation for how

evolution occurs in a book called what?evolution occurs in a book called what?

The Origin of The Origin of SpeciesSpecies

This book This book explained that explained that evolutionevolution occurs by occurs by means of means of naturalnatural selectionselection

What is Natural Selection?What is Natural Selection?

The process by The process by which which individualsindividuals that are better that are better adapted to their adapted to their environmentenvironment are are more likely to more likely to survive and survive and reproduce than reproduce than other members of other members of the same the same speciesspecies

What are the factors that affect What are the factors that affect the process of natural selection?the process of natural selection?

OverproductioOverproductionn

CompetitionCompetitionVariationsVariationsSelectionSelection

How does overproduction affect How does overproduction affect natural selection?natural selection?

So many So many speciesspecies are are produced that produced that there are not there are not enough enough resourcesresources (food, water, (food, water, and living and living space)space)

How does competition affect How does competition affect natural selection?natural selection?

Since Since foodfood and and other resources other resources are limited, the are limited, the offspring must offspring must competecompete in in order to surviveorder to survive

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How do Variations affect natural How do Variations affect natural selection?selection?

Any Any differencedifference between individuals between individuals of the same species of the same species is called a is called a variationvariation

Some variations of a Some variations of a species may provide species may provide an an advantageadvantage over over the other members the other members of the species of the species without the variationwithout the variation

How does the environment select How does the environment select which organisms survive?which organisms survive?

Individuals that are Individuals that are better better adaptedadapted to to their environment are their environment are more likely to more likely to survivesurvive and reproduce and reproduce passing on the helpful passing on the helpful traittrait to the next to the next generationgeneration

In effect, The In effect, The environmentenvironment “selects” those “selects” those organisms with helpful organisms with helpful traits to be the parents traits to be the parents of the next generationof the next generation

How is natural selection related How is natural selection related to evolution?to evolution?

Over a Over a longlong period of period of time, natural selection time, natural selection can can leadlead to evolution to evolution

Helpful variations Helpful variations gradually gradually accumulateaccumulate in in a species, while a species, while unfavorable ones unfavorable ones disappeardisappear

What role do genes “play” in What role do genes “play” in evolution?evolution?

Darwin did not know Darwin did not know anything about anything about genesgenes or or mutationsmutations so he could not so he could not explain what caused explain what caused the variations or how the variations or how they were passed onthey were passed on

Only traits that are Only traits that are inheritedinherited, or , or controlled by controlled by genesgenes, , can be acted upon by can be acted upon by natural selectionnatural selection

Evolution Controversy Video ClipsEvolution Controversy Video Clips

http://http://www.cbsnews.com/www.cbsnews.com/video/watch/?video/watch/?id=657122nid=657122n

Section 2: Evidence of EvolutionSection 2: Evidence of EvolutionWhat evidence supports the theory of What evidence supports the theory of

evolution?evolution?

FossilsFossilsPatterns of Patterns of EarlyEarly DevelopmentDevelopment

Similar Similar BodyBody StructuresStructures

What are homologous structures?What are homologous structures?

Body parts that Body parts that are structurally are structurally similar similar in in related species; related species; provide provide evidenceevidence that that the structures the structures were inherited were inherited from a from a commoncommon ancestorancestor

Do whales and humans share an Do whales and humans share an ancestor?ancestor?

Scientists have Scientists have recently found recently found fossils of fossils of ancient whale-ancient whale-like creatures like creatures that show that that show that they had they had legslegs and walked on and walked on landland

How do scientists infer How do scientists infer evolutionary relationships among evolutionary relationships among

organisms?organisms?

Similarities in Similarities in DNADNA

Protein Protein StructureStructure

Fossils Fossils Early Early

DevelopmentDevelopment Body Body

StructureStructure

What is one thing scientists use What is one thing scientists use to show how organisms are to show how organisms are

related?related?

A A branchingbranching tree – a tree – a diagram that diagram that shows how shows how scientists scientists think different think different groups of groups of organismsorganisms are are relatedrelated

How do new species form?How do new species form?

GeographicGeographic isolation – when isolation – when some members of some members of a species become a species become cutcut off from the off from the rest of the speciesrest of the species

Once members Once members are are isolatedisolated they they can no longer can no longer mate with mate with members of the members of the rest of the rest of the speciesspecies

Section 3: The Fossil RecordSection 3: The Fossil RecordWhat is a fossil?What is a fossil?

The preserved The preserved remainsremains or or tracestraces of an of an organismorganism that that lived in the pastlived in the past

Can be formed Can be formed from a from a bonebone, , tooth, shell, or tooth, shell, or other part of an other part of an organismorganism

Prehistoric SnakePrehistoric Snake

http://http://www.guardian.co.uk/www.guardian.co.uk/science/2009/feb/04/science/2009/feb/04/snake-giant-fossil-snake-giant-fossil-titanoboatitanoboa

How do fossils form?How do fossils form?

Most fossils Most fossils form when form when organisms organisms that that diedie become become buried in buried in sedimentssediments (particles of (particles of soil and rock)soil and rock)

What are petrified fossils?What are petrified fossils?

A fossil A fossil formed when formed when mineralsminerals replace replace allall or or partpart of an of an organismorganism

How are mold and casts related How are mold and casts related to fossils?to fossils?

Mold – A type of Mold – A type of fossil formed when fossil formed when shell or other hard shell or other hard part of an organism part of an organism dissolvesdissolves, leaving , leaving an an emptyempty space in space in the shape of the partthe shape of the part

Cast – A type of Cast – A type of fossil that forms fossil that forms when a when a moldmold becomes becomes filledfilled in in with minerals that with minerals that then hardenthen harden

Wooly MammothWooly Mammoth

http://http://www.cbsnews.com/www.cbsnews.com/video/watch/?video/watch/?id=4622301nid=4622301n

How else are remains preserved?How else are remains preserved?

Entire organisms, Entire organisms, such as the huge such as the huge elephant-like elephant-like mammoths have mammoths have been preserved in been preserved in iceice

Bones and teeth Bones and teeth have been preserved have been preserved in in tartar pitspits

Insects and other Insects and other organisms can organisms can become stuck in become stuck in sticky sticky sapsap. The sap . The sap then hardens forming then hardens forming amberamber

How do you determine a fossil’s How do you determine a fossil’s age?age?

RelativeRelative datingdating

RadioactivRadioactivee dating dating

What is relative dating?What is relative dating?

A technique used A technique used to determine which to determine which of of twotwo fossils is fossils is olderolder

Can only be used Can only be used when the rock when the rock layers have been layers have been preservedpreserved in their in their original sequenceoriginal sequence

What is radioactive dating?What is radioactive dating?

A technique used A technique used to determine the to determine the actualactual age of a age of a fossilfossil

The The rocksrocks that that fossils are found fossils are found near contain near contain radioactiveradioactive elements, elements, scientists use scientists use these elements these elements to determine to determine decay (decay (half-lifehalf-life))

What are radioactive elements?What are radioactive elements?

UnstableUnstable elements that elements that decay, or decay, or break down, break down, into different into different elementselements

What is half-life?What is half-life?

The time it takes for The time it takes for halfhalf of the of the atomsatoms in in a sample to decaya sample to decay

Scientists can Scientists can compare the amount compare the amount of a of a radioactiveradioactive element in a sample element in a sample to the amount of the to the amount of the elementelement into which into which it breaks downit breaks down

What do fossils reveal?What do fossils reveal?

Fossils help scientists Fossils help scientists piece together piece together information about information about Earth’s Earth’s pastpast

The The millionsmillions of fossils of fossils that scientists have that scientists have collected are called the collected are called the fossilfossil record record

When is a species extinct?When is a species extinct?

A A speciesspecies is is extinct if no extinct if no members of members of that species that species are still are still alivealive

What else does the fossil record What else does the fossil record provide?provide?

CluesClues about how and about how and when new groups of when new groups of organisms organisms evolvedevolved

The first animals The first animals ((invertebratesinvertebrates) ) appeared in the sea appeared in the sea about 540 million years about 540 million years agoago

About 500 million years About 500 million years ago, fishes evolved ago, fishes evolved (the first (the first vertebrates))

410 million years ago 410 million years ago the first the first plantsplants evolved evolved

What is the Geological Time What is the Geological Time Scale?Scale?

Scientist have used Scientist have used the the agesages of rocks of rocks and fossils to create and fossils to create a “calendar” of a “calendar” of Earth’s history that Earth’s history that spans spans 4.64.6 billion billion years years

Scientists have Scientists have divided this large divided this large time period into time period into smaller units called smaller units called eraseras and periods and periods sometimes called the sometimes called the GeologicGeologic Time Scale Time Scale

How is the Geological Time Scale How is the Geological Time Scale Divided?Divided?

Pre-cambrianPre-cambrianPaleozoicPaleozoic Era EraMesozoic EraMesozoic EraCenozoicCenozoic Era Era

What is the largest span of time What is the largest span of time in the Geologic Time Scale?in the Geologic Time Scale?

PrecambrianPrecambrian TimeTime

Covers the first Covers the first 44 billion years billion years of Earth’s of Earth’s history – very history – very fewfew fossils exist fossils exist from this time from this time periodperiod

What are the theories on how What are the theories on how fast does Evolution Occur?fast does Evolution Occur?

GradualismGradualism – – Evolution Evolution occurs occurs slowlyslowly but steadily but steadily (Darwin)(Darwin)

Punctuated Punctuated Equilibria – Equilibria – Species evolve Species evolve during short during short periods of periods of rapidrapid change change