Download Natural Selection

Natural Selection
• Natural Selection- Individuals best suited
to their environment survive and
reproduce most successfully.
• Adaptations- inherited traits that increase
an organism’s chance of survival.
• Because of these adaptations, a species
changes over time- Evolution.
Evolution evidence
• Fossil Record
• Geographic Distribution of living species
Fossils
• Paleontologist- scientist that study fossils
• Fossil record provides evidence about the
history of life on earth.
• Relative dating- estimate age by fossil
position in the sediment. Top layers are
the youngest, bottom layers the oldest.
• Absolute dating- age calculated from
amount of radioactive atoms remaining in
fossil. This is most accurate
Fossil Dating
• Fossil record-
•
Order of
fossils in
sedimentary
rocks.
Relative
dating.
Absolute
Dating or
Radiometric
dating of
fossils
Geologic Time Scale
• Precambian- Life begins 4.6 billion years ago
• Paleozoic- greatest diversity of marine life
• Mesozoic- flowering plants and Dinosaurs
• Cenozoic- Age of the Mammals- Humans
appeared.
More definitions
• Extinction- Disappearance, or dying out, of a
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species
Speciation- formation of a new species
Gene pool- all of the genes in a population
Adaptive radiation- process in which one species
evolves into diverse species according to
environment. Ex- Darwin’s finches
Biogenesis- Life arises from life
Spontaneous generation- life can arise from
nonliving matter .
Scientists
• Redi- 1st to try to prove biogenesis
• Pasteur proved Biogenesis
• Miller and Urey-explained how life could
have arisen from primitive earth. Carbon
dioxide, electricity, ultraviolet radiation
and water.
Figure 26.9 Louis Pasteur
Figure 26.9 Pasteur and biogenesis of microorganisms (Layer 3)
Figure 26.10 The Miller-Urey experiment YouTube - Tree of Life video HD
Darwin
• Charles Darwin- 1809-1882
• HMS Beagle 1831
• Did not use the word
evolution, but instead “Descent
with modification”
• Natural selection
• Tree of life
Natural Selection =
Populations + Environment
Populations
Environment
• Exhibit Variations
• Limited Resources
• Possess enormous
• Competition
reproductive potential
Natural Selection on a population
• In most populations, a trait that has the highest
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fitness, leads to a greater numbers of organisms
with this phenotype.
Stabilizing Selection- the populations tends to
exhibit the middle of the curve- average
Directional Selection- populations tend to exhibit
one trait.
Disruptive Selection-The extremes of the
population are favored. The normal is not
favored.
Speciation- formation of a new species
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Founding of a new population
Geographic isolation
Reproductive isolation
Competition
Resources and environment
PEPPERED MOTH
Darwin’s Finches
Small Tree Finch
Photo courtesy of Dr. Bob Rothman. http://www.rit.edu/~rhrsbi/HomePage/homepage.html
Large Cactus Finch
Finches
Photo courtesy of Dr. Bob Rothman. http://www.rit.edu/~rhrsbi/HomePage/homepage.html