TOPIC: Evolution
AIM: What evidence supports the theory of evolution?
How does Charles Darwin explain evolution?
Evolution: __________________________________________________
Geologic Time Scale: History of life
• Earth= 4.5 billion years old
• Organisms have evolved from _____________________________________
Evidence for Evolution
1. FOSSILS: _______________________________________________
• Bones
• Imprint = impression in mud that hardens into rock
• Mold = shape preserved in rock in hollow form
• Cast = mold filled with minerals that hardens
• Petrifaction = remains turn into stone
2. ANATOMICAL EVIDENCE: similarities in structure
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HOMOLOGOUS STRUCTURES
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__________________________________________________________
3. EMBRYOLOGICAL EVIDENCE
4. BIOCHEMICAL SIMILARITIES
similar DNA, proteins (hormones & enzymes)
What does this evidence suggest? _________________________________________________________
Where are fossils found?
• Layers of sedimentary rock
• LAW OF SUPERPOSITION: ____________________________________
_____________________________________________________________
Fossil Record
• Record of organisms that lived in past
• Incomplete (gaps), bc not all turn into fossils
ADAPTATION: Inherited trait
• Favorable: _________________________________________________________________________
• Ex: Camouflage
Charles Darwin: Galapagos Islands (1830’s)
Darwin’s Model of Evolution
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He was amazed by the variety of life on the islands.
Darwin observed 13 species of finches on the Galápagos Islands that were similar except for differences in
body size, beak shape, and eating habits.
Hypothesis: All organisms migrated from Central and South America.
• Species become adapted to their environments.
• Evolved over time into different species.
He noticed that all finches were similar to 1 finch he saw on the
South American coast.
Darwin reasoned that the Galápagos finches must have had to
compete for food.
Finches with beak shapes that let them eat food survived longer &
reproduced more than finches without those beak shapes
After many generations, these groups of finches became separate
species
Main Points of Natural Selection
1. Overproduction
• More offspring than can survive
• Better adapted à survive & reproduce
2. Competition
• Limited resources à compete à
more adapted will survive & reproduce
3. Variation
• __________________________________
• Better adapted à survive & reproduce
• Ex: Polar bears with thicker fur
(Darwin wasn’t able to explain where variations came
from)
4. Survival of the Fittest
• Most “fit” (favorable adaptations) will survive &
reproduce
5. Speciation
• Over generations, favorable adaptations stay &
unfavorable adaptations disappear à NEW
SPECIES
RATE OF EVOLUTION
1. GRADUALISM
• Evolution slow & continuous through time
2. PUNCTUATED EQUILIBRIUM
• Evolution fast & sudden changes after long period of no change *BOTH THEORIES SEEMED TO HAVE OCCURRED DURING EARTH’S HISTORY*
What organisms evolve quickly?
• Reproduce at very fast rate
• (bacteria, insects)
What organisms evolve quickly?
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(bacteria, insects)
Ex: Many bacteria have evolved
resistant to certain antibiotic
Sources of Genetic Variation in a Species
1. ______________________________
3. _________________________
2. ______________________________
4. __________________________
What can cause EXTINCTION?
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Major environmental change à adaptation no longer favorable à all organisms
die à extinction