Download Genetic Drift - stephen fleenor

Warm-Up (2/8)
On the piece of white paper from the back, answer
the following question.
How does artificial selection
promote faster evolution than
natural selection?
Name
Date
Period
1A.1f In addition to natural selection, chance and random events can influence the
evolutionary process, especially for small populations.
1A.3 Evolutionary change is also driven by random processes.
1A.3a: Genetic drift is a nonselective process occurring in small populations.
1A.3b: Reduction of genetic variation within a given population can increase the
difference between populations of the same species.
Genetic Drift
The Fleenzaurs in
China are the same
species, but a
different population.
A population is a
group which interbreeds.
ff
ff
Ff
Ff
Ff
FF
FF
ff
ff
Ff
FF
Genetic Drift
Allele Frequency
In large populations,
allele frequencies stay
the same unless there
is selection.
Generations
Genetic Drift
In small
populations,
allele frequency
can change
randomly, very
quickly.
= “genetic drift”
Genetic Drift
Populations
dramatically
reduced in size
(such as during a
natural disaster) are
subject to genetic
drift.
= “bottleneck
effect”
48% blue
52% yellow
78% blue
87% blue
22% yellow 13% yellow
Critical Thinking Question #1
Two varieties of Fleenzaurs are present in a
population: those with furry heads, encoded by the
fh+ allele; and those with bald heads, encoded by
the fh– allele. Predict how the balance of fh alleles
in the Fleenzaur population might change if only a
small number of individual Fleenzaurs are present.
Critical Thinking Question #2
A population of tropical birds, H. tropicalis, live on
an island in the Pacific Ocean. They are unable to
fly to the closest island, which is 50 miles away.
State one factor limiting their genetic variation, and
predict how the genetic variation would change of
a subset of the population which were able to
migrate to the closet island.
Closure
On the piece of white paper from the
back, answer the following question:
Predict how genetic drift would
be affected by a reduced
population size.
Name
Date
Period
Scale
1 – 10