Review For Final Exam
Chapter 11: The Evolution of
Populations
11.1: Genetic Variation Within
Populations
• A population is made of all of the
individuals of a species that live in an
area.
• A population shares a common gene pool.
• The gene pool of a population is the
combined alleles of all of the individuals in
a population.
11.1: Genetic Variation Within
Populations
• Genetic variation in a population increases
the chance that some individuals will
survive.
• Genetic variation comes from several
sources, and is stored in a population’s
gene pool.
• An allele frequency is how common an
allele is in the population.
11.2: Natural Selection in
Populations
• Populations, not individuals, evolve.
• Natural selection acts on a distribution of
traits.
• Natural selection can change the
distribution of a trait in one of three ways:
directional selection, stabilizing selection,
and disruptive selection.
• Microevolution is the change in allele
frequencies of a population over time.
11.3: Other Mechanisms of
Evolution
• Natural Selection is not the only
mechanism through which populations
evolve.
• Other ways populations evolve are gene
flow, genetic drift, and sexual selection.
• Gene flow is the movement of alleles
between populations.
• Gene flow increases genetic variation.
11.3: Other Mechanisms of
Evolution
• Genetic drift is a change in allele
frequencies due to chance.
• Genetic drift decreases genetic variation.
• Genetic drift occurs in small populations.
• Sexual selection occurs when certain traits
increase mating success.
• Example of sexual selection: female
guppies like males with bright colored
spots.
11.5: Speciation Through Isolation
• New species can arise when populations
are isolated.
• Populations can become isolated in
several ways.
• The isolation of populations can lead to
speciation.
• Speciation is the rise of two or more
species from one existing species (i.e. the
creation of a new species).
11.6: Patterns in Evolution
• Evolution occurs in patterns.
• Evolution through natural selection is not
random.
• Species can shape each other over time.
• Species can become extinct.
• Speciation often occurs in patterns.
11.6: Patterns in Evolution
• When two unrelated species develop similar
traits, it is called convergent evolution.
• Example: wings of birds and wings of insects.
• Divergent evolution is when two closely related
species become very different through evolution.
• Example: kit fox and red fox are very different
species that evolved from the same common
ancestor.
11.6: Patterns in Evolution
• Coevolution is when two or more species
evolve in response to changes in each
other. E.g. bees and flowers.
• Extinction is the elimination of a species.
• Extinction is a natural process of evolution.