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Title: Population Genetics and Evolution
Description: Biology notes on population genetics and evolution basics, including the Hardy-Weinberg Equilibrium Theory and Equation. These notes are from first year general biology II lecture
Description: Biology notes on population genetics and evolution basics, including the Hardy-Weinberg Equilibrium Theory and Equation. These notes are from first year general biology II lecture
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Bio Chapter 22, 23, and 24 Notes
Population Genetics and Evolution
Evolution and Natural Selection:
A) Definitions
•
Evolution- A change in allelic frequencies in a population over generations
•
Natural Selection- Differential survival and reproduction those individuals
possessing adaptations over those lacking these adaptations
o Primary mechanism of evolution, not the only one
o Those possessing individuals will be selected for by nature and those
lacking will be selected against
•
Natural selection à evolution à speciation à biological diversity
o Individual à population à community à community or higher
•
Speciation- The proliferation of life forms (species)
•
Biological Diversity- The number of species residing in a specific area
B) Examples of Natural Selection à Evolution
•
Tap dancing birds (red-cheeked cordon blue birds)
•
Male peacock spiders
•
Trait must be heritable and variable in population with selection pressure (what is
it in nature that is driving the process)
•
Figure out which individuals are selected for and selected against
•
Hermit crab caterpillar:
o Ability to build a traveling cocoon and retreat quickly into it
o Selection pressure = predation
o Camouflaged and size = good; selected for
o Not camouflaged and wrong size = bad; selected against
o Evolution- population is comprised of individuals that have camouflaged
and correct size cocoons
Hardy Weinberg Equilibrium Theorem:
A) Equation
•
p2 + 2pq + q2 = 1
...
0
•
Allelic frequencies vs genotypic frequencies
o Allelic frequencies:
§
Relate to p and q
o Genotypic frequencies:
§
§
q2 = frequency of homozygous recessive
§
•
p2 = frequency of homozygous dominant
2pq = frequency of heterozygous
Be able to apply the equation to problems (fig 23
...
485)
o Example:
§
Given the allelic frequency of A (red flowers) =
...
8 and q =
...
64 = red flowers
•
aa = 0
...
32 = pink flowers
B) Point of Equation
•
There will be no evolution if the population meets all five conditions
•
No evolution means that allelic frequencies do not change over generations
C) 5 Conditions for NO Evolution
•
A large population
•
Random mating
•
No migration
•
No mutation
•
No selection (natural or artificial)
D) Negating the 5 Conditions
•
A large population (10,000+)
o To negate, population becomes small, so evolution can occur via genetic
drift
o Genetic Drift- Unpredictable fluctuations in a allelic frequencies due to a
small population
§
Two sub-categories of genetic drift:
•
Bottleneck Effect- A population remains where it was
historically but goes through a reduction in size due to a
catastrophe (random chance event)
o Bad luck not bad genes
o Ex
...
•
Founder Effect- A population is started in a new location
separate from the historic location that is small and does
not represent the larger population from where it came
(based on the allelic frequencies from where it came); small
population remains in the new location (does not migrate
back)
•
Random mating
o To negate, there is non-random mating (choice), so evolution occurs
because of differential reproduction
o Differential Reproduction- Some individuals get chosen, and some do
not
o Note- many aquatic invertebrates (sponges, sea anemone, etc
Title: Population Genetics and Evolution
Description: Biology notes on population genetics and evolution basics, including the Hardy-Weinberg Equilibrium Theory and Equation. These notes are from first year general biology II lecture
Description: Biology notes on population genetics and evolution basics, including the Hardy-Weinberg Equilibrium Theory and Equation. These notes are from first year general biology II lecture