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1.
2.
3.
4.
Compare and Contrast How is mass extinction
different from background extinction
Relate Cause and Effect Why would evolution
speed up when a small group of organisms
migrates to a new environment
Relate Cause and Effect Why does adaptive
radiation sometimes result in convergent
evolution
Infer What role does the environment play in
convergent evolution
CH 19 HISTORY OF LIFE
19.2 Patterns and Processes of Evolution




The fossil record shows a parade of organisms that
evolved, survived for a time, and then disappeared
More than 99 percent of all species that have lived
on Earth are extinct
How have so many different groups evolved
Why are so many now extinct.
Macroevolutionary Patterns



Transformations in anatomy, phylogeny, ecology,
and behavior that occur in clades
If more speciation than extinction occurs the clade
survives
If more extinction than speciation occurs the clade
dies out.
Macroevolution and Cladistics

Fossils are also classified into clades.

Background extinction
 Slow

but steady process of natural selection
Mass extinction
 Affects many
species over a relatively short period of
time
 Entire ecosystems vanish and whole food webs
collapse.




After mass extinction
Survivors produce new species to fill empty niches
Biodiversity recovers
Takes between 5 and 10 million years.
Gradualism

Slow, steady change
in a particular line
of descent.
Punctuated Equilibrium

Long lengths of
stability that is
interrupted by brief
periods of more rapid
change.
Rapid Evolution



Occurs more often in a small population
Occurs more often when migrating to new area
Occurs more often after a mass extinction.
Adaptive Radiation


Single species or a small group of species evolves
over a relatively short time into several different
forms that live in different ways
Occurs when species migrate to a new
environment or when extinction clears an
environment of a large number of inhabitants.
Convergent Evolution

Different groups develop the same adaptations due
to living in similar environments
 These
all eat ants and termites.
Coevolution

Two species evolve in response to changes in each
other over time
 Flowers
and pollinators.
1 What is plotted on the y-axis
2 Which mass extinction killed of the highest percent
of genera
3 Describe the overall pattern of extinction
4 What evidence
is the graph
probably based
on