EVOLUTION UNIT

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EVOLUTION UNIT

• Evolution is the development of new types of
  organisms from preexisting organisms or the
  change in organisms over time.

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Population Genetics

• Chapter 16 pgs. 317 - 325

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Population genetics is the study of evolution
from a genetic point of view.
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Remember the goldenrod!

• There is variation in the traits of a population.
• These traits are phenotypes that are the result
  of genes.

Usually the data fits a bell curve
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What causes genetic variation?

• 1. Mutations a random change in genetic code
  passed on to offspring.
• 2. Meiosis the reshuffling of genes during
  crossing over and independent assortment
• Creating genetically unique gametes

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• 3. Random pairing of gametes from mating and
  fertilization

Which gamete will end up on the flower?
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The Gene Pool

• Describes the total genetic information available
  in a population
• Includes all the different alleles for a trait

Ex dog fur traits
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The Gene pool (cont)

• Allele Frequency how often a certain allele ends
  up in a gamete (see sickle cell lab)
• The frequency of an allele in a population can
  change over generations
• It is not always 50/50! Some alleles are rare.

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Hardy Weinberg Principle

• This theorem states the frequencies of alleles
  (and genotypes) in a populations gene pool will
  remain constant over generations unless acted
  upon by distruptive agents.
• Gives us a baseline or reference point to
  consider what forces cause changes in populations
  traits.

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Five Conditions if Equilibrium is to stay the
same.

• 1. Large populations

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Five Conditions if Equilibrium is to stay the
same.

• 2. Isolation from other populations no one
  moves in or out.
• No Immigration
• No Emigration

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Five Conditions if Equilibrium is to stay the
same.

• 3. No genetic mutations

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Five Conditions if Equilibrium is to stay the
same.

• 4. Mates are randomly found.

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Five Conditions if Equilibrium is to stay the
same.

• 5. No natural selection all traits have equal
  reproductive success

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The next section is for the very brave who want
to look at the math principles at work behind the
Hardy-Weinberg Equilibrium but it is NOT
REQUIRED!
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Wildflower Population

• Lets take a population of Wildflowers 500
  individuals in all.
• Pink Flowers 480 White - 20
• A
  a
• 320 AA 160 Aa
  20 a
• Total of alleles in this population is 1000

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Wildflowers

• How many total A?
• AA 2 x 320 640
• Ana 1 x 160 160
• 800/1000 0.8
• How many total a
• Ana 1 x 160 160
• a 2 x 20 40
• 200/1000 0.2

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How can we calculate the next generation?

• What is the probability that AA will show up?
• 0.8 x 0.8 0.64 or 64 AA

• What is the probability that a will show up?
• 0.2 x 0.2 0.04 or 4 a

• What is the probability that Aa will show up?
• (0.8 x 0.2) (0.2 x 0.8) .32

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Hardy-Weinberg Equation

• 1-p q or 1-q p
• p2 2pq q2 1
• If deviated from this ? evolution takes place.

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Causes of Evolution

• Genetic Drift Changes in the gene pool of a
  SMALL population due to chance.
• Our wildflower population is now at 25
• 16 AA 8Aa 1aa
• A 0.8 a 0.2
• Passing Herbivore eats 3 AA
• A 0.77 a 0.23