Class notes
Biol 141 Natural Selection Notes
- Institution
- University Of Wisconsin - Whitewater
This is a comprehensive and detailed note on natural selection for Biol 141. *Essential Study Material!!
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Unit 07 AP Biology Master HyperDoc of Expectations and ResourcesNatural Selection: 13-20% of AP Exam
Big Ideas~ 1: Evolution (EVO), 2: Energetics (ENE), 3: Information Storage & Transmission (IST), 4: System Interactions (SYI)
EXPECTATIONS: This is a LARGE Unit, we will use two exams to assess.
Topic Learning Targets (I can ) and Success Criteria (I am learning how …)
Learning targets are in bold with their success criteria listed beneath
7.1 Introduction to Natural Selection
Describe the causes of natural selection. EVO-1.C
Natural selection is a major mechanism of evolution.
According to Darwin’s theory of natural selection, competition for limited resources results in differential
survival. Individuals with more favorable phenotypes are more likely to survive and produce more offspring,
thus passing traits to subsequent generations.
Explain how natural selection affects populations. EVO-1.D
Evolutionary fitness is measured by reproductive success.
Biotic and abiotic environments can be more or less stable/fluctuating, and this affects the rate and direction of
evolution; different genetic variations can be selected in each generation.
7.2 Natural Selection
Describe the importance of phenotypic variation in a population. EVO-1.E
Natural selection acts on phenotypic variations in populations.
Environments change and apply selective pressures to populations.
Some phenotypic variations significantly increase or decrease fitness of the organism in particular environments.
7.3 Artificial Selection
Explain how humans can affect diversity within a population. EVO-1.F
, Through artificial selection, humans affect variation in other species.
Explain the relationship between changes in the environment and evolutionary changes in the
population. EVO-1.G
Convergent evolution occurs when similar selective pressures result in similar phenotypic adaptations in
different populations or species.
7.4 Population Genetics
Explain how random occurrences affect the genetic makeup of a population. EVO-1.H
Evolution is also driven by random occurrences -
a. Mutation is a random process that contributes to evolution.
b. Genetic drift is a nonselective process occurring in small populations -
i. Bottlenecks.
ii. Founder effect.
c. Migration/gene flow can drive evolution.
Describe the role of random processes in the evolution of specific populations. EVO-1.I
Reduction of genetic variation within a given population can increase the differences between populations of the
same species.
Describe the change in the genetic makeup of a population over time. EVO-1.J
Mutation results in genetic variation, which provides phenotypes on which natural selection acts.
7.5 Hardy-Weinberg Equilibrium
Describe the conditions under which allele and genotype frequencies will change in populations. EVO-1.K
Hardy-Weinberg is a model for describing and predicting allele frequencies in nonevolving population.
Conditions for a population or an allele to be in Hardy-Weinberg equilibrium are - (1) a large population size, (2)
absence of migration, (3) no net mutations, (4) random mating, and (5) absence of selection. These conditions
are seldom met, but they provide a valuable null hypothesis.
Allele frequencies in a population can be calculated from a genotype frequencies.
RELEVANT EQUATION
Hardy-Weinberg Equation -
p2 + 2pq + q2 = 1
p = q =
1
where:
p = frequency of allele 1 in the population
q = frequency of allele 2 in the population
Explain the impacts on the population if any of the conditions of Hardy-Weinberg are not met. EVO-1.L
Changes in allele frequencies provide evidence for the occurence of evolution in a population.
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