Date post: | 26-May-2015 |
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Lab Intro: Genetic Drift
But first….
Evolution Review What is natural selection? How does natural selection relate to the struggle to
survive? – What are some environmental factors that create that struggle
Explain the concept of overproduction of offspring – How does that relate to the idea of population capacity?
What is inherited variation? • Why is it so very important?
• What are some dangers of loosing it? How does all of this relate to differential reproductive
success?
Biodiversity Review
What is biodiversity? Explain what “biodiversity = stable
ecosystem” really means?– What constitutes a stable ecosystem?
How is biodiversity decreased? How is biodiversity increased? What are some consequences of a loss
of biodiversity?
Genetic Variation
A loss of genetic variation = a loss of what?
Why is genetic uniformity so dangerous?
And now.. GENETIC DRIFT!
Genetic Drift is: FLASHCARD ALERT: GENETIC DRIFT: Random, non-adaptive
change in the gene frequencies (aka genetic variation) of a population – What do you think they mean by non-adaptive?
Usually reduces genetic variation– Which genes get eliminated happens by chance
Affects smaller populations much more than large populations.
Two types: Bottleneck Effect & Founders Effect
Example: Population of flowers: Red and White Through random chance the elimination of the white
flower occurs (I.e it gets trod on) This loss in genes to a small population means that
certain combinations cannot reproduce Over time the small population of flowers will be all
red.
Natural Selection vs. Genetic Drift
QuickTime™ and a decompressor
are needed to see this picture.
The Bottleneck Effect
FLASHCARD ALERT: BOTTLENECK EFFECT: – A situation where a large population is
drastically reduced in size • Could be a result of:
– natural disasters
– Invasive species
– Epidemic etc. etc.
Which does what to the genetic variation of the population?
Example: The California Sea Otter
Past 10 years: dying at an alarming rate– Infected with Toxoplasma
Gondii– Increased pollution– Loss of habitat
Almost Extinct – 1990: <100 otters– 1993: 2,200 otters
Now scientists are again having issues with successful population growth – Result of the bottleneck effect.
Founder Effect
FLASHCARD ALERT: – FOUNDER EFFECT: colonization of a new
habitat by only a few individuals
Again: reduce of genetic variation In the right circumstances it will lead to
speciation and eventually evolution of new species – New environment - new challenges - different
adaptations are beneficial - natural selection
Example: The Afrikaner population of Dutch Settlers in Africa Dutch immigrants in
1652 One man carried the
gene for Huntington’s disease – Dominant gene
Now there is an alarmingly high frequency of the disease in that region of Africa