BSC 2011L Exam Prep-Questions With Complete
Solutions
Fitness
the ability of an organism to produce viable offspring
Adaptation
a heritable trait that is associated with high fitness - promotes a population's survival and
reproduction in a particular environment
Theory
an explanation or set of hypotheses that attempt to explain a large and pervasive phenomenon
Directional Selection
occurs on a trait when one extreme phenotype is favored - causes the frequency curve to shift to
either the left or right
Impacts of Directional Selection on Traits
1. The average changes, because individuals with one extreme have higher fitness while
individuals with another extreme have lower fitness
2. The amount of overall variation decreases, because alleles associated with one extreme are
being eliminated
Stabilizing Selection
,occurs on a trait when individuals with the average value have highest fitness and individuals
with both extreme phenotypes have lower fitness - causes the frequency curve to become
narrower around the average phenotype
Impacts of Stabilizing Selection on Traits
1. The average does not change, because individuals with intermediate values of the trait have
the highest fitness
2. The amount of overall variation decreases, because alleles associated with both extremes are
being eliminated
Genetic Drift
any change in allele frequencies that is due to chance - can lead to allele fixation or loss, and has
a much larger effect on allele frequencies in small populations versus large populations
Founder events
occur when a relatively small number of individuals disperse to a new habitat and found, or
establish, a completely new population - causes genetic drift and reduces genetic variation in the
affected population
Bottleneck events
occur when a species undergoes a large and rapid decrease in population size due to a disease
epidemic, catastrophic storm, or other change - alleles that survive do so largely by chance.
Causes genetic drift and reduces genetic variation in the affected population
Gene Flow
, causes allele frequencies to change when individuals and their alleles move from one population
to join another population - makes allele frequencies in two populations more similar
(homogenizes allele frequencies among populations). This change can be maladaptive in a new
environment
Evolution
a change in allele frequencies over time - can be adaptive or random
Mutation
any change in the nucleotide sequence in DNA - the only process that creates entirely new
alleles, and thus, genetic variation
Hardy-Weinberg Principle
the null model for testing whether or not evolution is occuring - predicts the offspring genotypes
and their frequencies in a gene pool. Assumes no gene flow, no selection, no mutations, no
genetic drift, a large population, and random mating
Hardy-Weinberg Equation
p² + 2pq + q² = 1
p: frequency of dominant allele
q: frequency of recessive allele
p²: % of individuals who are homozygous dominant
q²: % of individuals who are homozygous recessive
Hardy-Weinberg Equilibrium
Solutions
Fitness
the ability of an organism to produce viable offspring
Adaptation
a heritable trait that is associated with high fitness - promotes a population's survival and
reproduction in a particular environment
Theory
an explanation or set of hypotheses that attempt to explain a large and pervasive phenomenon
Directional Selection
occurs on a trait when one extreme phenotype is favored - causes the frequency curve to shift to
either the left or right
Impacts of Directional Selection on Traits
1. The average changes, because individuals with one extreme have higher fitness while
individuals with another extreme have lower fitness
2. The amount of overall variation decreases, because alleles associated with one extreme are
being eliminated
Stabilizing Selection
,occurs on a trait when individuals with the average value have highest fitness and individuals
with both extreme phenotypes have lower fitness - causes the frequency curve to become
narrower around the average phenotype
Impacts of Stabilizing Selection on Traits
1. The average does not change, because individuals with intermediate values of the trait have
the highest fitness
2. The amount of overall variation decreases, because alleles associated with both extremes are
being eliminated
Genetic Drift
any change in allele frequencies that is due to chance - can lead to allele fixation or loss, and has
a much larger effect on allele frequencies in small populations versus large populations
Founder events
occur when a relatively small number of individuals disperse to a new habitat and found, or
establish, a completely new population - causes genetic drift and reduces genetic variation in the
affected population
Bottleneck events
occur when a species undergoes a large and rapid decrease in population size due to a disease
epidemic, catastrophic storm, or other change - alleles that survive do so largely by chance.
Causes genetic drift and reduces genetic variation in the affected population
Gene Flow
, causes allele frequencies to change when individuals and their alleles move from one population
to join another population - makes allele frequencies in two populations more similar
(homogenizes allele frequencies among populations). This change can be maladaptive in a new
environment
Evolution
a change in allele frequencies over time - can be adaptive or random
Mutation
any change in the nucleotide sequence in DNA - the only process that creates entirely new
alleles, and thus, genetic variation
Hardy-Weinberg Principle
the null model for testing whether or not evolution is occuring - predicts the offspring genotypes
and their frequencies in a gene pool. Assumes no gene flow, no selection, no mutations, no
genetic drift, a large population, and random mating
Hardy-Weinberg Equation
p² + 2pq + q² = 1
p: frequency of dominant allele
q: frequency of recessive allele
p²: % of individuals who are homozygous dominant
q²: % of individuals who are homozygous recessive
Hardy-Weinberg Equilibrium
