Transcript Adaptive Radiation

Macroevolution
“Large-scale changes in living things, and the
production of dramatically new forms of life…”
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Mass extinctions
Adaptive radiation
Convergent evolution
Divergent evolution
Coevolution
Gradualism
Punctuated equilibrium
Mass Extinctions
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More than 99% of all
species that ever lived
are now extinct
 5 mass extinction
events in Earth’s history
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Wipes out whole
ecological systems
 (Ex: dinosaurs extinct
during K/T event)
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Burgess Shale (many
extinct organisms that
were VERY different
from modern
organisms)
Adaptive Radiation
Remember Darwin’s Finches?
► What was Darwin’s theory about how they came
to have different beak sizes?
► Adaptive Radiation…
Adaptive Radiation
Darwin proposed that all the finches evolved from a
single ancestral species
► Each island had a different physical environment, and
unique plant species were dominant on each one
► Different plants produced seeds of different sizes, some
large, some small
► Over time, the finches best-adapted for the available
food on each island produced the most offspring, and
became the dominant type in each location
► Due to the distance between the islands, the finches
became isolated and no longer bred easily with finches
on other islands, leading to distinct species, each with a
unique beak size (Speciation)
► This evolutionary process is called Adaptive Radiation
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Convergent Evolution
Unrelated organisms,
sometimes on
different continents,
appear to resemble
one another quite
closely, because of
similarities in their
NICHE...
Convergent Evolution
Because their selection pressures are similar, unrelated
organisms on different continents often display similar adaptations
Divergent Evolution
► Isolated
populations of a
species evolve independently
► Example:
black bear
and polar bear:
related but different
fur color
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Coevolution
Two organisms evolve together as a result of their
interdependence (symbiosis)
Ex: The Star Orchid has a long spur containing a supply of
nectar in its tip. The Giant Hawk Moth has an equally long
proboscis that enables it to feed on the nectar, and pollinate
the flower. Neither species can survive w/o the other!
Gradualism
Slow, steady
changes in
the size and
shape of
bones…
Punctuated Equilibrium
Some families display an evolutionary
pattern of long, stable periods
interrupted by brief periods of more
rapid change.
Theories of Change
► Has
evolution happened very slowly and
gradually, with organisms always changing
slightly from generation to generation? (this
was Darwin’s view…)
► Or
is evolution characterized by long periods
without change, followed by explosions of
diversity (ex. The Burgess Shale)?
► The answer is………BOTH!
Evolution of Birds Based on Fossil Evidence
Gradualism vs. Punctuated Equilibrium
Does evolution affect
individuals, populations, or
gene pools?
Population Genetics
The study of genetic traits and
changes in populations.
Population
Genetics
1. Gene pool
The combined genetic
information of all the
members of a
particular
population.
Population Genetics
2. Allele frequency
Is the number of times that an
allele occurs in a gene pool
compared with the number of
times other alleles occur (ex.
beans and bunnies lab).
Population Genetics
3. Genetic equilibrium
Allele frequencies remain constant.
this even possible in a changing
environment?......
► Is
Population Genetics
4. Hardy-Weinberg principle
Allele frequencies in a population
will remain constant unless one or
more factors cause those
frequencies to change.
Population Genetics
5 Conditions to maintain
genetic equilibrium
1. Random mating
2. Population must be very large
3. No immigration/emigration
4. No mutations
5. No natural selection!
Therefore, if the gene frequency of a population changes
then it must have “evolved”!
Population Genetics
5. Genetic drift
Random and rapid changes in allele
frequencies that often occur in
small populations
 No obvious “selection pressures”,
just random changes that can occur
rapidly when there is in-breeding in a
closed population
What does the future hold for
OUR species…?