Warm Up 2/27
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What is allele frequency?

What are the four ways evolution occurs?
Evolution Island

Finish the lab now!!
After the Lab

Staple all Teammates’ papers together.

I will grade 1 of them…. You don’t know whose it is.
Quick Review…
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Change in allele frequency in a population is called
EVOLUTION

Change in allele frequency due to random/chance is called (remember
the coywolves)
Genetic Drift

A change in the DNA sequence that offers an advantage and results in
that change being passed on to other generations is evolution by
Mutation

Change in allele frequency in a population due to MIGRATION is:
Gene Flow

Change in allele frequency due to selection pressures in their
environment is called:
Natural Selection
3 Different Types of
Natural Selection
1.
Disruptive
2.
Directional
3.
Stabilizing
Disruptive Selection

Disruptive selection – FAVORS EXTREMES

It is a type of natural selection that selects against the
average individual in a population.

Disruptive selection is the rarest of the three types of natural
selection.
Disruptive Selection

Remember, it favors EXTREMES.
London Peppered Moth
Industrial areas – black moths.
Rural areas – light colored moths.
Very few medium colored moths.
Stabilizing Selection

Stabilizing selection – FAVORS AVERAGE

It is a type of natural selection that favors the
average individuals in a population.

This process selects against the extreme
phenotypes

Diversity in a population is decreased due to
stabilizing selection
Stabilizing Selection - Example

Stabilizing selection works mostly on traits that are polygenic.

Since stabilizing selection favors the middle of the road, a
blend of the genes is often what is seen.

Many human characteristics are a result of stabilizing
selection.
Human birth weight is not
only a polygenic trait, but it is
also controlled by
environmental factors.
Infants with average birth
weight are more likely to
survive than a baby that is
too small or too large.
Directional Selection

Directional Selection – FAVORS *ONE* EXTREME

Think – this drives selection in one DIRECTION over the other

This phenomena is usually seen in environments that have
changed over time. Changes in weather, climate, or food
availability lead to directional selection.
Directional Selection - Example
The Texas Longhorn is an example of the effects of directional
selection. The long horns were advantageous for defending young
calves from predators - so horn length increased in feral herds in the
American Southwest between the early 1500s-1860's. The trend is
now maintained through artificial selection by ranchers. Do you
think the horn length would change if the now predator-free cattle
were not being selected for artificially?
So when you think of
DIRECTIONAL Selection…

Think of…
Moon Bounce
Choose one person to be the astronaut. The other
teammates hold each elbow and waist of the
astronaut. Count 3-2-1, the astronaut jumps and
the teammates boost the astronaut at the top of
their jump.
Types of Natural Selection

http://educationportal.com/academy/lesson/types-of-naturalselection.html
Scenario 1

Tongue length in anteaters in polygenetic and
therefore tongues come in a range of lengths.
Give (1) example of how directional selection
might be acting upon this trait, with a graph and
pictorial representation.

If it was particularly hot one summer and ants
were making their hills farther below the surface,
anteaters with shorter tongues wouldn’t be able
to find food.
Practice Scenarios

You will receive a scenario – work it in your spiral.

When everyone at your table is done, rotate the
scenarios.

Once you have completed all 4, compare with
your team.
Teams for your scenarios….
Team 1
Team 2
Team 3
Team 4
Team 5
Team 6
Team 7
Alexia
Addison
Lance
Alexa
Luis
Malcolm
Benjamin SC
Dirk
Ashleigh
Lauren
Alexis
Benjamin S
Angela
Halea
Justin
Anthony G
Rebecca
Henry
Kaila
Thomas
Anthony R
Susan
Matthew
Jonathan
Christopher
Ethan
Noe
Teams for your scenarios
Team 1
Team 2
Team 3
Team 4
Team 5
Team 6
Team 7
Kendall
Jonathan
Aria
Cuauhtli
Mattison
Wynton
Jessica
Gregory
Kate
Destinylynn
Laura-Claire
Contessa
Grace
Sarah
Ashlee
Emily
Carlos
Tanner
Dakota
Maia
Abraham
Carson
Abel
Cameron
Kayla
Matthew G
Emilio
Liam
Kallysta
Briana