Download Agents of Change

Wednesday, February 8th
Agents of Evolutionary Change
(what causes change in populations?)
Five Agents of Evolutionary Change
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Mutation
Gene Flow
Nonrandom Mating
Genetic Drift
Selection
Expert Groups
• You will split up into Expert Groups to study
one of these 5 agents of change.
• For ~8 minutes you’ll read, learn, and become
an Expert about your particular Agent with
your Expert Group
• After, we will form 2 groups where each
Expert will teach everyone else their group
about the Agent of Change they studied
What Information
should an Expert Know?
• Definition of your Agent that is in your own
words (No Science-y Gobbly Gook)
• How your Agent affects allele frequency in a
population
• If our population consisted of us in this room,
devise a situation/example how your Agent
could cause a change in the allele frequency
within our population
Genetic Drift – Founder Effect
Genetic Drift – Bottleneck
Types of Selection - Disruptive Selection
• Favors both of the
extremes and selects
against the common trait
• Darwin’s Finches are
thought to have been an
example of this
• Beaks were either suited
for larger or smaller seeds,
but medium sized beaks
weren’t great for either.
Types of Selection – Directional Selection
• One phenotype is favored
at one of the extremes of
the distribution
• This “weeds out” one of
the phenotypes
• In this case, smaller body
sizes are selected against
and larger body sizes are
selected for
Types of Selection – Stabilizing
Selection
• Organisms in a
population with extreme
traits are eliminated
• Stabilizing Selection
favors general/common
traits as opposed to
extreme
• ex: birth weight
Some Independent Reading
• I’d like you to read pg 404 (beginning with
Selection to avoid predators) to the end of
20.5 on page 407.
• Take notes to summarize the material
• Answer:
– the Inquiry question at the top of page 406
– Review Questions Understand #2, 4, 5; Apply #3