EVOLUTION
Review Scientists who contributed to the theory of
evolutionMechanisms for evolution
Charles Darwin
In your own words, describe what YOU think the theory of evolution means…
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?
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 (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.
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?
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
Lamarck’s Theory of Evolution
Tendency toward Perfection Tendency toward Perfection (Giraffe necks)(Giraffe necks)
Use and Disuse (bird’s using forearms)Use and Disuse (bird’s using forearms) Inheritance of Acquired TraitsInheritance of Acquired Traits
Are you still paying Attention?Are you still paying Attention?
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 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
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?