Lesson 4 Agenda

1
Lesson 4 Agenda

• Mechanisms of Evolution
• NO ISLAND BIOGEOGRAPHY next Monday
• Continue discussion of mechanisms for selection
• PowerPoint Slide Show with questions throughout
• Ms. Bakers Recommendation Take notes!
• Copies of the slides are available online
•  
• Organization Time
• This time is dedicated to
• 1) Grade checks with Ms. Henshaw
• 2) Organizing Week 2
• 3) Asking questions
• Week 2 Due Date
• Week 2 Packet will be due at the beginning of
  class on
• MONDAY, May 6th, 2013
• Feel free to turn it in today if you dont want
  to worry about it over the weekend!

2
Genghis Khan

• According to historical researchers, Genghis Khan
  was responsible for the death of over 40,000,000
  during his 20 year reign.
• Some modern scientists say it is possible that
  Genghis Khan has between 16,000,000 and
  25,000,000 living descendants.
• Do you think Genghis Khan was a fit individual?
• Why or why not?
• Have any other humans in history
• been as successful as Genghis Khan
• in terms of genetic fitness?

3
RadioLabMaking of the Fittest
4
Genghis Khan

• According to historical researchers, Genghis Khan
  was responsible for the death of over 40,000,000
  during his 20 year reign.
• Some modern scientists say it is possible that
  Genghis Khan has between 16,000,000 and
  25,000,000 living descendants.
• Do you think Genghis Khan was a fit individual?
• Why or why not?
• Have any other humans in history
• been as successful as Genghis Khan
• in terms of genetic fitness?

5
5 Mechanisms of Evolution

1. Random Mutation
2. Gene Flow (aka Migration)
3. ? (Hint this is were we ended last class)
4. ?
5. ?

6
Remember back to last class3. Genetic Drift
Reduction of Genetic Variation
Random Death
Small Beginning Population
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3. Genetic Drift

• Bottleneck Event

• Founder Effect

Different events, similar results reduced
genetic variation
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Bottleneck Events
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Founder Effect
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Comparing Types of Genetic Drift
Type of Event Original Population New Population
Bottleneck
Founder Effect
Dramatically reduced
Random bad luck
Reduced genetic variation
Reduced genetic variation
Migration
Still present, but far away
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Remember back to last class3. Genetic Drift

• Bottleneck Event

• Founder Effect

• Population bottlenecks occur when a populations
  size is dramatically reduced for at least one
  generation

• A founder effect occurs when a new colony is
  started by a few members of the original
  population. 

Different events, similar results reduced
genetic variation
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Genghis Khans Conquests

• Is this an example of genetic drift?
• If you think it is, was this an example of
• a bottleneck or of the founder effect?
• If not, what evidence do you have to
• say that this is not genetic drift?

13
5 Mechanisms of Evolution

1. Random Mutation
2. Gene Flow (aka Migration)
3. Genetic Drift
4. ?
5. ?

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4. Non-Random Mating
Non-random mating occurs when there is a bias for
or against mating with certain individuals.
For example Sexual Selection http//www.p
bs.org/wgbh/evolution/library/01/6/l_016_09.html
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5 Mechanisms of Evolution

1. Random Mutation
2. Gene Flow (aka Migration)
3. Genetic Drift
4. Non-Random Mating
5. ? (Hint Its the primary mechanism for
   evolution!)

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Hold on now

• What was that learning target again???

I can explain how natural selection works as the
primary mechanism for evolution.
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Evolution via Natural Selection

• Genetic variation
• Struggle for existence
• Differential survival reproduction
• Production of offspring

• http//www.dnatube.com/video/11928/Natural-Selecti
  on-and-Adaptation

18
Think Pair Share
Your friend says to you, Malaria caused sickle
cell to show up in humans What would you say
to your friend to help them better understand
this relationship?
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5. Natural Selection
Natural selection works because some phenotypes
are more successful than others in a given
environment.
Successful (adaptive) genotypes become more
common in later generations, causing a change in
gene frequency over time that leads to increase
in fitness!
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5. Natural Selection
Natural selection leads to adaptation an
increase in the frequency of fit genes of a
population in a particular environment.
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Think Pair Share
Is domestication and the selective breeding of
crops and livestock a form of natural selection?
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Three Forms of Natural Selection
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Human Birth Weight Is Under Stabilizing Selection

• What effect can modern medicine have on selection?

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Directional Selection in cacti population

• Does the cacti choose to have more thorns?

25
Disruptive Selection in the Grand Canyon
Kaibab squirrel (Sciurus aberti kaibabensis,
left) and Abert squirrel (Sciurus aberti aberti,
right) became geographically isolated about
10,000 years ago.
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Think Pair Share
How can pure chance (mutation) create new complex
structures or processes, much less new species?
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Think Pair Share
Does the theory of natural selection suggest an
optimistic or a pessimistic view of the world?
28
Think Pair Share
Mutations happen randomly, without regard to how
they effect, an organism. That said, does
having the sickle cell mutation benefit or harm a
human organism? What effect can an individual
having a mutation that is beneficial in a certain
environment have on the population?
29
Think Pair Share
Why do we still have wisdom teeth if dentists
just pull them out?
30
Next Week

• Island Biogeography Lab
• The Canary Islands
• http//www.youtube.com/watch?vSC4ctwvbo1w
• http//www.youtube.com/watch?vaLMV_vUfcvs