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Accelerated Biology
Section 13.1 – The Theory of Evolution by Natural Selection
Read each question, and write your answer in the space provided.
1. List two observations made by Charles Darwin during his 5 year voyage that led him to conclude that
living specie evolved from extinct species.
Fossils of armadillos that closely resembled living armadillos.
Organisms on the Galapagos islands closely resembled those on the mainland.
2. Describe how natural selection occurs
Individuals with traits well–suited to their environment are more likely to survive and
reproduce than individuals without such traits.
3. Summarize the MODERN theory of evolution by natural selection
Genetic variations in a population enable some organisms to produce more offspring
than others. Overtime, the frequency of beneficial alleles will increase.
4. Compare the punctuated equilibrium model of evolution to the gradualism model.
Punctuated – evolution occurs in spurts in response to strong environmental pressures
Pocket mouse changed color after the soil light  dark after lava flow
Moths around London changed color after trees turned dark due to pollution
Gradualism – specie evolve gradually over long periods of time.
5. Speciation can result when two populations have become
B – Reproductively isolated – When two populations of the same species to not breed
with each other over long periods of time because of their geographic isolation.
Ex) When the individuals of two related populations can no longer breed with one
another, the two populations are considered to be different species.
When the Colorado River formed the Grand Canyon 10,000 years ago a population of
squirrels become isolated from one another.
Kaibab – North Rim of the Grand Canyon
Abert Squirrel – South rim of the Grand Canyon
They are now separate species.