Download How Populations Evolve

How Populations
Evolve
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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.
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Natural Selection
• Study by Peter and Rosemary Grant
• Galapagos - Birds with beaks most
suited to drought environment (tough
seeds) survived and reproduced
• Average beak size increased
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Natural Selection
Other Examples
bacteria/antibiotic resistance
tuskless elephants
insects/pesticide resistance
peppered moths
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Types of Natural Selection
Directional
Stabilizing
Disruptive
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Evolution
• Change in the genetic composition
of a group of organisms over time.
• Descent with modification
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Microevolution
•
•
Changes within species
Short Time Period
• e.g. Tuskless elephants
• e.g. Peppered Moths/Coloration
• e.g. Bacteria/Antibiotic Resistance
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Macroevolution
• Changes over longer time periods
• Speciation - evolution of 2 or more
species from a single species
Species B
Species C
Species A
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Causes of Evolution
• Natural Selection
• Artificial Selection
• Genetic Engineering
• Mutation
• Non-Random Mating
• Genetic Drift
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Artificial Selection
Humans select which individuals breed
Wild Rose
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Garden Rose
Artificial Selection
Humans select which individuals breed
Wild Rose
Wild Maize
Wolf
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Horticultural Roses
Modern Corn
Modern Dog Breeds (Fig 15.8)
Genetic Engineering
•Tobacco with Firefly Gene
•Bt Corn - has bacterial gene making
it resistant to insects
•Golden Rice - Has genes for beta
carotene
•Mr. Green Genes - cat with
bioluminescent gene from jellyfish
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Mutation
• Any change in the DNA.
• Due to mistakes in
replication
• Or to exposure to
radiation or certain
chemicals
• Source of new genes
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DVD
Natural Selection and Adaptation
in rock pocket mice
http://www.hhmi.org/biointeractive/shortfilms/
index.html
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Adaptation
•
Structure, function, or behavior that helps
an organisms survive and reproduce
•
•
•
•
Flower color
Spines
Waxy
CAM
photosynthesis
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Cactus with
Flowers
Adaptation
•
Structure, function, or behavior that helps
an organisms survive and reproduce
• Color
• Position on Trees
• Broad Wings
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Peppered Moth
Non-Random Mating
• Individuals mate with like individuals
• Increases the number of homozygous (AA, aa)
individuals.
• Decreases heterozygous (Aa) individuals
AA
AA
Aa
AA
Aa
Aa
aa
AA
Aa
AA
aa
40% AA, 40% Aa, 20% aa
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AA
Aa
AA
AA
aa
AA
aa
AA
AA
60% AA, 10% Aa, 20% aa
Genetic Drift
Changes in gene composition due to chance.
Most obvious in small populations
AA
Aa
AA
AA
aa
Aa
Aa
AA
Aa
AA
aa
40% AA, 40% Aa, 20% aa
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Aa
AA
Aa
Aa
AA
AA
aa
AA
AA
60% AA, 30% Aa, 10% aa
Bottleneck Effect
After disaster, small population, different
composition
Before:
60% Blue
40% Green
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After:
80% Blue
20% Green
Founder Effect
New population starts from larger population
Different Genetic Composition
e.g. Polydactylism 6 fingers more
common in Amish
due to single
founding individual
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Figure 16.7
The End
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