Download Natural Selection and Evolution

Natural Selection
and Evolution
Thursday, January 17, 2013
Scientific Inquiry
• Scientists interpret data based on
observation, prior knowledge and
experience.
• Ideas change as new data is found
• e.g. Fossil bones --->Pterosaur
• e.g. Fixity of species--->Evolution
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Charles Darwin
• Variety
• Overproduction
• Limited
Resources
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Theory of Natural Selection
Those individuals with the
traits most suitable to their
environment are more likely to
survive and reproduce and
pass those traits on to the next
generation.
Thursday, January 17, 2013
Activity - Beak shape and
Feeding Success
Trial
1
2
3
Average
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Test Tube
Tweezers
Holder
Tongs
Hose
Clamp
Activity - Beak shape &
Feeding Success
Tweezers
1
2
3
4
5
6
Thursday, January 17, 2013
Test Tube
Holder
Tongs
Hose
Clamp
Activity - Beak shape
and Feeding Success
Tweezers
Competition 1
Competition 2
Thursday, January 17, 2013
Test Tube
Holder
Tongs
Hose
Clamp
Peter and Rosemary Grant
• based at Princeton
• researched in Galapagos
• started in 1973, went back
each summer for many years
• Documented natural selection
• Results described in book “The
Beak of the Finch”
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Daphne Major
•
•
•
•
small island
no human habitation
difficult to reach
1 species of ground finch
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Measuring
•
•
•
•
tagged and measured all birds
beak - length, width, strength
bird weight, gender, etc.
variety of beak sizes
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•
•
•
•
Seed Analysis
Also measured seed types and
abundance of each.
Initially a wide variety of types.
Abundance decreased
drastically during drought in
1977/1978
Only the toughest seeds to open
remained
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Population Drop
•
•
•
Finch population dropped from
1400 to less than 200 during the
drought
No reproduction that year
Average beak depth increased
from 9.4 mm to 10.1mm
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Bacteria and Antibiotic
Resistance
• No exposure - most of
population not
resistant
• exposure - mostly
resistant individuals
survive
• After exposure - most
resistant
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Insects & Pesticide Resistance
• No exposure - most of
population not
resistant
• exposure - mostly
resistant individuals
survive
• After exposure - most
resistant
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Peppered Moths
• Manchester,
England
• Pre-industrial Typica form
common
• 1895 98%
Carbonaria form
• Late 1900’s
typica common
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Tuskless Elephants
• Asian elephants
• Poachers kill for
tusks
• Incidence of
tuskless males
increasing
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Types of Selection
•Directional
•Stabilizing
•Disruptive
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Original Population
# of
individuals
with trait
Measurable Trait
e.g. Beak size, plant height, etc.
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Directional Selection
•Selection in favor of one extreme
Larger beak
size
# of
individuals
with trait
Beak size
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Stabilizing Selection
•Selection against extreme in favor
of middle
# of
individuals
with trait
birth weight
of mammals
Birth weight in mammals
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Disruptive Selection
•Selection against middle
Tall weeds do
best in fields
Short weeds
do better on
mowed lawns
# of
individuals
with trait
Plant Height
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The End
Thursday, January 17, 2013