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Genetic Drift
Add in gene flow
Cheetahs
What is genetic drift?
Genetic drift: any event that randomly
changes the gene pool and often
decreases genetic variation
Example 1: Reproductive
Chance
Example 2: Disasters! Fire,
Lightning, Earthquake, Tsunami, etc
Selective Breeding
• Selective Breeding is the process of
breeding plants and animals together to
get the most desired traits
• Selective breeding = artificial selection
(It’s not a natural process)
• Scientists will typically take two organisms,
each with helpful mutations and cross
them
Selective Breeding Examples
• Farming
• Breeding of
animals
Thoroughbred Horses
When does genetic drift have a big
impact?
• Genetic drift has the biggest impact
when the population is small.
What are two types of genetic drift
that have a big impact?
1. Bottleneck effect: the result of a disaster
event which greatly reduces population
size, including decreased genetic
variation
Another way of thinking about the
bottleneck effect
What are two types of genetic drift
that have a big impact?
2. Founder effect: the result of starting a
new population with a small number of
individuals, including changes in the gene
pool and decreased genetic variation
Compare genetic drift to natural
selection
Genetic Drift
Both
Natural
Selection
In genetic drift,
the survivors
are just lucky
because
genetic drift
is completely
random.
Genetic drift
and natural
selection are
both ways
that
populations
change/
evolve.
In natural
selection, the
survivors are
those with
advantageous
traits.