Present-Day Evidence For
Evolution
“Observing Evolution In Action”
Natural Selection
• Is there any evidence of Natural Selection
taking place in real populations?
• One study, performed during the industrial
revolution in England, demonstrated that
populations of organisms ARE greatly
affected by environmental changes
The Peppered Moth
• Two different forms of the moth existed
• One Dark form, one Light
• Both forms were common
Natural Selection At Work
• What kind of tree
would you expect the
Dark forms to sleep
on?
• What kind of tree
would you expect the
Light form to sleep
on?
The Effect Of A Changing Environment
• What do you think might have happened to the
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trees that were near coal-burning factories and
power stations?
They became covered in black carbon soot
What do you predict might then have happened
to the moth populations in these areas?
In heavily industrialized areas, the Light form of
the moth almost disappeared, because of
predation
The Dark form became dominant in these areas
because of Natural Selection
Antibiotic Resistance
• Because Bacteria reproduce so quickly,
they represent excellent specimens for
testing Natural Selection
• Watch how quickly they can “evolve”
because of Natural Selection…
Natural Selection In The Galapagos
• Remember Darwin’s
Finches? What was
Darwin’s theory about
how they came to
have different beak
sizes?
Adaptive Radiation
• Darwin proposed that all the finches evolved from a
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single ancestral species
Each island had a slightly different environment, and
unique plant species were dominant on each one
Different plants produced seeds of different sizes, some
large, some small
Over time, the finches best-adapted for the available
food on each island were produced the most offspring,
and became the dominant type in each location
Due to the distance between the islands, the finches
became isolated and no longer bred easily with finches
on other islands, leading to separate species each with a
unique beak size (Speciation)
This evolutionary process is called Adaptive Radiation
Evolution in your lifetime.
• Bacteria are evolving in your life time into
new forms antibiotics does not kill.
• Plants have evolved in the past few year
into forms that herbicides such as roundup
do not kill.