The Evolution of an IDEA!!!

Objectives:1.Describe the contributions of early scientists to modern theories of evolution2.Explain the fundamental theory of evolution3.Discuss some questions and ideas that shaped Darwin’s thinking

In your own words, describe what YOU think the theory of evolution means…

Charles Darwin

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 did Darwin came up with his theory?

• …well first we have to have a look at those who came before Darwin.

• These people changed the way we look at the world around us.

• Darwin’s theory was greatly influenced by the following people.

Ideas that shaped Darwin’s Thinking

James Hutton:James Hutton: 1795 - Theory of Geological 1795 - Theory of Geological

changechange Forces are changing the Forces are changing the

shape of the Earth’s surface shape of the Earth’s surface These changes are very These changes are very

slowslow The Earth is much older The Earth is much older

than the thousands of years than the thousands of years we once thought!we once thought!

George Cuvier: Fossil Studies• (1769 – 1832)• He noted that fossils can be simple or complex • Fossils of simpler organisms seem to be found in

deeper layers of rock and soil• Fossils of more complex organisms seemed to be

found at relatively shallower depths• The shallower the depth a fossil is found in, the more

closely it is likely to resemble a living species• He also noted that some rock layers contained fossils

of organisms that didn’t occur in any other layer

• Theory of Catastrophism: Catastrophes like floods caused extinctions of species (which could be found in the fossil layers) and these species were replaced by new species.

Charles Lyell: Theory of Uniformitarianism• 1797-1875• Published ‘Principles of Geology’• Earth has been changed in the

past and is still changing now• Geological change is very slow• Hypothesized that mountains were

and are still being formed by gradual processes and areas of land are being slowly worn/eroded away

Darwin thought if the Earth changed over time, what about life on the Earth?

Lamarck

Lamarck's Principles

1. Use and Disuse: Structures an animal used became bigger and stronger, while structures that were not used became smaller and weaker.

2. Inheritance of Acquired Characteristics: An animal could pass on the traits it had acquired throughout its life to its offspring

What did we get from Lamarck??

• Lamarck hypothesized that…• All species evolve over time.• A species evolves in response to its environment

so that it is better able to survive (adaptation)• Changes get passed on from generation to

generationLamarck’s theory, while flawed got the ball rolling

for modern day thinking about how and why species change.

Population Growth – Why do species need to change???

Thomas Malthus-19th century English economist

If populations grew indefinitely(more Babies born than die) Insufficient living

space Food runs out Darwin applied this

theory to animals

On to Darwin…The 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/revolutionary hypothesis/theorytheory about how about how life changes over timelife changes over time

Patterns of Diversity (Questions) 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.

Why??? Wouldn’t similar environments be home to Why??? Wouldn’t similar environments be home to similar species??similar species??

Patterns of Diversity

Darwin posed challenging questions. Darwin posed challenging questions. Why were there no rabbits in Australia, despite the Why were there no rabbits in Australia, despite the

presence of habitats that seemed perfect for them?presence of habitats that seemed perfect for them?

Why were there no kangaroos in England?Why were there no kangaroos in England?

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?

Publication of Origin of Species

Russel Wallace wrote Russel Wallace wrote an essay summarizing an essay 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

Your Task• Read through your hand out and answer

questions 1-3.

• For HOMEWORK tonight!!• Read Adaptive Radiation: Darwin’s Finches

to learn more about what Darwin discovered on his voyage.

• Answer the questions• I am away tomorrow. There will be a QUIZ

on Thursday based today’s lesson and your work tomorrow!

Mechanisms for Evolution

Natural variationNatural variation--differences among --differences among individuals of a speciesindividuals of a species

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

usefuluseful..

Artificial Selection

Other Mechanisms that Drive Evolution Sexual Selection: the process Sexual Selection: the process

by which a trait that enables by which a trait that enables an organism to acquire more an organism to acquire more mates becomes more mates becomes more common. common.

Males compete for females Males compete for females (combat)(combat)

Females chose males Females chose males (desirable traits)(desirable traits)

Genetic Variation Evolution requires genetic variation.Evolution requires genetic variation. New genes being introduced results in diversity of New genes being introduced results in diversity of

offspring.offspring. Mutations: Source of genetic variationMutations: Source of genetic variation Light and Dark MothsLight and Dark Moths

Dark Moths increased in frequency during Dark Moths increased in frequency during industrial revolution because of dark soot in airindustrial revolution because of dark soot in air

Dark Moths could hide from birdsDark Moths could hide from birds

Descent

Descent with ModificationDescent with Modification-Each living organism has -Each living organism has descended, with changes from other species over timedescended, with changes from other species over time

Common DescentCommon Descent- were derived from common ancestors- were derived from common ancestors

Evidence of Evolution

The Fossil RecordThe Fossil Record Comparative Comparative

anatomy/Homologous Body anatomy/Homologous Body StructuresStructures

Similarities in Early Similarities in Early DevelopmentDevelopment

Biochemistry and DNABiochemistry and DNA Vestigial organsVestigial organs Observation of Direct Species Observation of Direct Species

ChangeChange

Evidence for Evolution

The Fossil RecordThe Fossil Record-Layer show -Layer show changechange

Shows numbers extinct animalsShows numbers extinct animals Shows similarities between extinct Shows similarities between extinct

animals and animals that are alive animals and animals that are alive todaytoday

The earth’s layers show a time The earth’s layers show a time scale of species and when they scale of species and when they appeared on earth (and when they appeared on earth (and when they died out)died out)

Transitional fossils Transitional fossils are fossils that show are fossils that show intermediary links intermediary links between groups of between groups of organismsorganisms

They can provide a They can provide a link between the past link between the past and presentand present

Biochemistry and DNA

When comparing When comparing the DNA of one the DNA of one species to species to another, more another, more similarities are similarities are found in species found in species that are more that are more closely related.closely related.

Direct observation of species change

Bacteria become Bacteria become resistant to resistant to antibioticsantibiotics

Wolves were bred over Wolves were bred over many generations to many generations to become dogs (become dogs (artificial artificial selectionselection) • and then ) • and then bred further to create a bred further to create a variety of breedsvariety of breeds

Your Task

With your partner, review the 4 With your partner, review the 4 mechanisms for evolution that you learned mechanisms for evolution that you learned about today. about today.

Explain each mechanism for evolution in Explain each mechanism for evolution in your own words. How do you think each of your own words. How do you think each of these mechanisms drove evolution?these mechanisms drove evolution?