Transcript Evolution

Biological Evolution
A change in the genetic characteristics of a
population over time
 If any allele frequency in a population
changes w/ time, the population is evolving
 Most people think of evolution as Darwin’s
speciation, but this is not correct

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Biological Evolution

Only populations can evolve; individuals
cannot
 (on
molecular level, genes can evolve)
Small scale change = microevolution
 Large scale change = macroevolution
 Macroevolution can lead to speciation, but
it does not have to

 macroevolution
that has occurred in dogs
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Mechanisms of Evolution

Evolution occurs through two major
genetic forces:

Natural Selection (includes artificial seltn)
 Genetic Drift

What are the other two forces that can
change allele frequencies in a population?

Mutations
 Gene flow
 Do
not generally cause evolution, mutation is too rare
& gene flow tends to equalize the gene frequencies
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Natural Selection Occurs because:
Organisms with favorable traits have a
better chance at survival
 The longer an organism lives, the more
offspring it may produce
 More of the next generation will have the
favorable trait than the previous
generation

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Genetic Drift


Differences in reproduction or survival between
organisms due to random chance
Environmental disturbances can cause genetic drift:

Hurricanes or Volcanic eruptions
 Clearing land for development or Over-hunting

Can be from random events
 seeds
from white flowers are blown to gravel, some
seeds from red flowers blown to good soil.
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Genetic Drift
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Result of Evolution

Evolution results in 3 major themes in
biology:
Adaptation of populations
2. Diversity of life
3. Shared inherited characteristics between
organisms
1.
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Adaptations & Diversity

Adaptation –a characteristic that improves
the survival of an organism
 The

result of natural selection
Diversity is the result of speciation
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Impact of Evolutionary Thought

Understanding evolution has impacted
technology:
 Development
and use of pesticides
 Antibiotics and the development of drug resistance

Doonesbury cartoon?
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Readings on Evolution


I have assigned the readings, but I have only
lightly covered this topic
Want to spend more time on Life on Earth
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Shared Inherited Characteristics

Characteristics
arise due to a
common ancestry:

Homologous
structures
 Vestigial structures
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Shared Non-Inherited
Characteristics
Convergent evolution in similar
adaptations
 These are considered analogous
structures


Thorns on roses and cactus
 Wings in birds and insects
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Evidence for Evolution

Fossils
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Evidence for Evolution

Organisms contain evidence of their
evolutionary history:
 Vestigial
structures
 Embryological development
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Evidence for Evolution



Continental drift
The lungfish existed
before the break up of
the super continent,
Pangaea
Living representatives
of the lungfish are all
over the world
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Evidence for Evolution

Direct observations of
genetic change in
populations

Artificial selection:
 Farming
crops
 Domesticated animals
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Evolution in Action

Medium ground finch
in the Galapagos

Changes in beak and
body size correlate
with rainfall over time
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Concept Quiz
Of the following situations that pertain to
evolution, which one is false?
A.
B.
C.
Organisms inherit traits from their parents.
Organisms can adapt to prepare their offspring
for future events.
Evolution can happen by chance.
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Concept Quiz
Evolution is the change that occurs in
__________ over time.
A.
B.
C.
a population
an organism
the environment
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Concept Quiz
Of the following, which term or phrase best
describes the process of natural selection?
A.
B.
C.
Genetic drift
Differential reproductive success
Speciation
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