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Chapter 2

Chapter 2 & 8 / Lecture 3


Department
Life Sciences
Course Code
LIFESCI 2D03
Professor
Brett Beston
Chapter
2

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The process of humans choosing certain varieties of an organism over others by implementing
breeding favoring one variety over the other
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Basically picking traits for both animals and plants that we find productive for our causes
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We can pick for both behaviour and physical traits
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Teosinte was the how the corn first looked, then now we have artificially selected for the corn
we know today
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Artificial Selection
Natural Selection
Any trait that helps the individual survive in their environment and increases fitness
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If this trait is heritable then it will be passed down the generations, in turn increasing it's
frequency
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Considering an animal's phenotype is representative of it's hunting behavior, then the
phenotype is a result of it's phenotype
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If an animal hunted in a group, it got more food which in turn increased it's fitness
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Gene variants are called allele, which are passed down the line
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Selective advantage of a trait
Variation- different forms of the trait
1)
Fitness consequences- the trait must affect reproductive success
2)
Inheritable- a means to pass it to future generation
3)
A fourth hidden condition is the scarcity of resources which is always met
4)
Natural selection operates on 3 conditions:
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How does Natural Selection operate?
There must be a selection, something Natural Selection can select between
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Genetic factors
1)
Environmental factors
2)
Things that cause variation are:
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Vp=VG+VE
Phenotypic variance= genetic variance + environmental variance
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Heritability (broad sense) = H2= Vg/ Vg+ VE
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Heritability (narrow sense)= H2= VA/VP
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Genetic variance: average amount of variance between genotypes
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Environmental variance: average amount of variance between individuals within the same
genotype
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Variation
DNA fails to replicate properly
i.
External factors (radiation)
ii.
1)
2)
Variation based on genetic factors can be caused in 3 ways:
-
Genetic factors
Chapter 2 & 8
Saturday, October 08, 2011
1:04 PM
LIFE SCI 2D03 Page 1
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