Download Patterns of Evolution

Patterns of Evolution
Genetic Drift
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Random change in allele frequency
In small populations, individuals that
carry a particular allele may leave
more descendants than other
individuals, by chance
Over time, these occurrences can
cause an allele to become common in
a population
Isolating Mechanisms
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As new species evolve, populations
become reproductively isolated from
each other.
Reproductive
Behavioral
Geographic
Temporal
Reproductive Isolation
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When the members of two populations
cannot interbreed and produce fertile
offspring.
Behavioral Isolation
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Occurs when two populations are
capable of interbreeding but have
differences in courtship rituals or other
reproductive strategies that involve
behavior
Geographic Isolation
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Two populations are isolated by
geographic barriers such as rivers,
mountains, or bodies of water.
Temporal Isolation
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Two or more species reproduce at
different times.
Macroevolution
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Refers to large-scale evolutionary
patterns and processes that occur over
long periods of time.
Extinction
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99% of all species that have ever lived
are extinct
Some mass extinctions have occurred
killing off entire ecosystems.
– These were believed to have occurred
due to a collapsing environment.
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These extinctions left room for new
species to evolve.
Adaptive Radiation
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Occurs when a single
species or a small group
of species has evolved,
through natural selection,
into diverse forms that
live in different ways.
Ex: Darwin’s finches:
more than a dozen
species evolved from a
single species.
Convergent Evolution
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Adaptive radiation can cause the production of
unrelated organisms that look remarkably similar
May occur when animals evolve in separate
locations under similar conditions and they develop
the need for similar structures.
Ex: swimming animals have a streamline body
(sharks, fish, dolphins, and penguins)
Divergent Evolution
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When species that were similar
become different.
Same as adaptive radiation.
Coevolution
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The process by which two species
evolve in response to changes in each
other over time
Ex: a flower changes color, odor, or
scent over time, so the pollinator may
also change