EVOLUTION

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EVOLUTION!

• Biology 2007

"It is not the strongest of the species that
survive, nor the most intelligent, but the one
most responsive to change." - Charles Darwin
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What is evolution?

• Scientific theory with a LOT of evidence
• Began in the late 19th century with Charles
  Darwin
• Evolution is not under attack- this is a common
  misconception
• Explains how the current diversity of life on
  Earth arose over time
• Explains how populations (not individuals) change
  over time

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Modern humans (Homo sapiens) appear about 2
seconds before midnight
Age of mammals
Recorded human history begins 1/4 second before
midnight
Age of reptiles
Insects and amphibians invade the land
Origin of life (3.63.8 billion years ago)
Plants invade the land
Fossils become abundant
Fossils present but rare
Evolution and expansion of life
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Descent with modification one ancestor spreads
into different species over time
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Darwin-Wallace Theory of Natural Selection

• aka survival of the fittest
• What does it mean to be fit?
• Operates on a population level
• Struggle for survival
• Why would individuals be struggling?
• Variation within the population
• How does this variation arise?
• Certain individuals have favorable traits
• These individuals leave more offspring
• Over time, the population changes

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How natural selection works
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FIGURE 14-9
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FIGURE 14-21
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FIGURE 14-25
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Adapted to cold through heavier fur, short
ears, short legs, short nose. White fur matches
snow for camouflage.
Northern population
Arctic Fox
Spreads northward and southward and separates
Different environmental conditions lead to
different selective pressures and evolution into
two different species.
Early fox population
Adapted to heat through lightweight fur and long
ears, legs, and nose, which give off more heat.
Southern population
Gray Fox
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FIGURE 15-6
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FIGURE 14-31
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FIGURE 15-7
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Evolution of Dinosaurs and birds
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Transitional forms- evidence for macroevolution
Archaeopteryx- sketch and fossil
Tiktaalik fossil
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FIGURE 14-13
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Sala-mander
Fruit Fly
Chicken
Rabbit
Human
Fish
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