Transcript Patterns and Processes of Evolution

Section 19-2: Patterns and Processes of
Evolution
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Fossil record shows that 99% of species that
have ever existed have gone extinct
Macroevolutionary patterns are grand
transformations in anatomy, phylogeny,
ecology, and behavior, usually taking place in
clades not individual species
Includes speciation, extinction, emergence of
larger clades
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Paleontologists study fossils, put them into
clades based on derived characters
Learn history of life
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As environments have changed, species either
adapt or go extinct
Rates at which species appear, adapt, and
become extinct vary
Emergence of new species in a clade impacts
macroevolution of the clade
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If “birth” of species is equal to “death” of species ,
clade will survive
Sometimes the more varied the clade more likely it
will continue
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Background extinction – species goes extinct
because of slow, steady natural selection
Mass extinction – many species go extinct over
a short period of time
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Entire ecosystems/food webs collapse
Change is too quick
Caused by asteroids, volcanoes, changing sea levels
Severely decreases biodiversity – some may survive
then flourish
Eventually recover in 5 to 10 million years
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Gradualism – slow,
steady change in a
line of descent
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Punctuated
equilibrium –
equilibrium
interrupted by brief
periods of rapid
change
New species created
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Small population becomes isolated from main
population, and can evolve faster
Small group of organisms migrates (finches)
Organisms survive mass extinction
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Evolutionary process by which a single species
or a small group of species evolves over a
relatively short time into several different
forms that live in different ways
Diversification of a clade
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Migration
Mass extinction
New adaptation
Examples in fossil record after extinction of
dinosaurs
Finches
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Process of evolution that produces similar
structures and characteristics in distantlyrelated organisms
Similar environments and selection pressures
Body parts with similar functions, may look
similar (analogous)
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Two species evolving in response to changes in
each other over time
Flowers and pollinators
Plants and herbivorous insects