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17-4 Patterns of Evolution
Macroevolution is a word meaning
large-scale evolutionary patterns and
processes that occur over long periods
of time
Extinction
• Usually, extinctions happen for Darwinian
reasons. Some species adapt and survive,
Others gradually become extinct in ways that
are caused by natural selection.
• Several times in the Earth’s history, however,
mass extinctions wiped out entire ecosystems.
Researchers have not yet determined the
precise causes of mass extinctions.
Adaptive Radiation
• Adaptive Radiation is when a species or a
small group of species has evolved, through
natural selection, into diverse forms that live
in different ways.
• The disappearance of the dinosaurs cleared
the way for the great adaptive radiation of
mammals.
Adaptive Radiation
The radiation of
mammals
produced the great
diversity of their
species during the
Cenezoic.
Convergent Evolution
• Convergent evolution is the process by which
unrelated organisms come to look like
eachother.
• Convergent evolution involving fishes, 2
groups of aquatic mammals, and swimming
birds has resulted in sharks, dolphins, seals,
and penguins whose streamlined bodies and
swimming appendages look the same
Coevolution
• The process where 2 species evolve in
responses to changes in eachother over time
is called coevolution.
• Many flowering plants, for example, can
reproduce only if the shape, color, and odor of
their flowers attract a specific type of
pollinator.
How is this an example of coevolution?
How is this an example of coevolution?
Coevolution
• Some of the most powerful poisons in nature
are plant compounds that have evolved in
response to insect attacks.
Punctuated Equilibrium
• At several points in the fossil record, changes
in plants or animals occurred over relatively
short periods of time. Some biologists suggest
that most new species are produced by
periods of rapid change.
• Scientists use the term punctuated equilibrium
to describe this pattern of long, stable periods
interrupted by brief periods of more rapid
change.
Punctuated
Equilibrium
Rapid evolution
after long periods
of equilibrium can
occur when a small
population
becomes isolated
from the main
population, genetic
changes can then
spread in the small
population very
fast.