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Patterns of Evolution
The term macroevolution is used to
describe large-scale evolution that takes
place over time
it is evolution above the species level
Six important topics in macroevolution
include: extinction, adaptive radiation,
convergent evolution, coevolution,
punctuated equilibrium, and changes in
developmental genes
Extinction is the disappearance, or
dying out, of a species
Most extinction occurs when species
cannot compete for resources or adapt to
changing environments (natural selection
at work)
Mass Extinction
Mass extinctions occur when entire
ecosystems are wiped out and many
species go extinct
Until recently, researchers looked for a
single cause of mass extinctions; however,
many paleontologists now think that most
mass extinctions are caused by many
Significance of Mass Extinctions
Each disappearance of so many
species left habitats open and
provided ecological opportunities for
those organisms that survived
the result was often a burst of evolution
that produced many new species
Adaptive Radiation
Adaptive radiation is the process in
which one species evolves into diverse
species that live in different ways
Example: Darwin’s finches → more than
a dozen species evolved from a single
species of finch
Adaptive Radiation
Adaptive radiations can also occur on a
much larger scale
Example: Dinosaurs vs. Early Mammals
The first dinosaurs and mammals evolved at
about the same time
The dinosaurs went through an adaptive
radiation that allowed them to “rule” Earth for
millions of years while mammals remained
small and were relatively scarce
Once the dinosaurs were out of the picture, the
mammals went through an adaptive radiation
Adaptive Radiation
Convergent Evolution
Convergent evolution is a process in which
“unrelated” species come to look alike
because they have evolved similar
adaptations to similar environments
Example: Similarities between sharks,
dolphins, and penguins – How did these
organisms come to resemble one another?
analogous structures - structures which
look and function similarly, but are made up
of parts that do not share an evolutionary
Coevolution is the process by which two
species evolve in response to changes in
each other
Example: some plants have evolved poisons
to protect themselves from insects → in
response, insects have evolved ways to
protect themselves from the poisons
Punctuated Equilibrium
Punctuated equilibrium is a pattern of
evolutionary change where long
periods of little or no change (in a
species) is interrupted by short periods
of rapid change
* Evolution occurs at different rates for
different organisms over time
Developmental Genes
Small changes in the development of
an embryo can have a large affect on
the adult organism