Transcript variation and artificial selection

7.1 Variation
7.2 Artificial Selection
What causes VARIATION?
Remember Genetics
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What causes VARIATION?
Remember Genetics
• offspring have a combination of genetic
material from both parents
• sexual reproduction (crossing over +
independent assortment) = variation
• genetic variation in a population results
from the variety of genetic information in
all individuals of the population
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What Causes
Variation?Mutations
• When the DNA is copied during
INTERPHASE (you have about 175
mutations compared to your parents DNA)
• Mutations in gametic cells can be passed
down and create change
• Mutagens: external factors that cause DNA
to change Ex: Ultraviolet radiation
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Are variations good or bad?
• It depends....
• Interaction with environments is what
determines if a variation of a trait is
advantageous or not.
• Variations can be advantageous / neutral /
harmful
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Are variations good or bad?
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Variations within a population are GOOD
- resistance to disease
- resistance to other changes
- allows for adaptations to develop
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Peppered Moth
• If ALL the moths were the same then they
would have ALL died. Variation allowed
this species to survive.
• Depending on the ENVIRONMENT
different VARIATIONS were “selected for”
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Peppered Moth
WHAT HAPPENED?
– Pollution caused the lichen to die
– Light peppered moths stood out
– Light peppered moths were eaten
– Dark moths survived and reproduced
– When the conditions changed the opposite
occurred
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Selective Pressure
• Environmental conditions that select for
certain characteristics and select against
others
– climate conditions
– predators present
– natural variations in habitat
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Artificial Selection
• Selective pressure exerted by humans on
populations in order to “improve” or
modify particular desirable traits
• Since the desirable traits are selected by
humans it may not be an improvement to
the species if left in nature
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Artificial Selection vs
Natural Selection
• SELECTIVE pressure
– Artificial: the selective pressure is HUMANS
or conscious human caused conditions
– Natural: the selective pressure is in NATURE
– & Natural Selection is SITUATIONAL
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Artificial Selection
• Has been happening for a VERY long time
– SELECTIVE BREEDING is another name for
Artificial Selection
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SELECTIVE BREEDING
• People select which
organisms to breed.
• based on desirable TRAITS
• desired by humans
• This leads to a higher
frequency of the desired traits
Doebley et al. In press.
Benefits of Artificial Selection in
Food Crops
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Higher yield
More desirable colour
Nutritional value
Drought - resistant
Pest - resistant
Grow quickly
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Artificial Selection in Animals
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Belgian Blue COW
• Cool Cows!
• http://www.youtube.com/watch?v=Nmkj5g
q1cQU
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Benefits to Artificial Selection
in Animal Agriculture
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Higher meat production
Less fat production
Higher milk production
Grow faster
Produce more eggs
Resistant to disease
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LINK TO DARWIN
“The circumstances under which our
domestic productions are reared are
widely different. . . In conformity with
this, all our domesticated productions,
with the rarest exceptions, vary far
more than natural species.”
-Darwin (1896)
Darwin took notes on the domestication of plants,
farm animals and dogs. He bred pigeons himself.
He used this as a springboard for his theory of
Evolution by means of Natural Selection