Transcript Evolution of Species

Evolution of
Species
Evolution of Species
• Species have the ability to interbreed and
produce fertile offspring in nature.
• Speciation is the evolution of a new species.
• Speciation can occur only when either
interbreeding or the production of fertile
offspring is somehow prevented.
For example, these happy face spiders look
different, but since they can interbreed, they are
considered the same species: Theridion
grallator.
Evolution of Species
• Physical barriers can prevent
interbreeding.
* Drought
* Shift in river flow
* Volcanic eruptions
* Sea level changes
Evolution of Species
• Geographic isolation occurs if a physical barrier
separates a population into groups.
• Geographical isolation prevents interbreeding and
gene exchange.
• Over time, each population would adapt to the local
environment through the process of Natural
Selection.
• Eventually, the gene pools of each group would
become so different that one could be considered a
new species.
Mode of
speciation
New species
formed from...
Allopatric
geographically isolated
populations
Peripatric
Similar to allopatric,
except only a small
population isolated at
the edge of a larger
population (the gene
pool of one becomes
very small)
Parapatric
Common in plants, the
ranges do not
significantly overlap
which give them a
narrow contact zone (or
the range is really
large)
Sympatric
Some reproduce as
their ancestors did (on
a certain type of fruit)
while others choose to
reproduce using their
current environment
(most abundant fruit)
Bison have come close to extinction due to
uncontrolled hunting, drought, and disease. There is
now very little genetic variation in bison populations.
Which of the following is a result of the limited
genetic variation in the current bison populations
compared to earlier bison populations with more
variation?
A. Bison in current populations are more resistant
to new diseases.
B. The survival rate of young bison has increased
in current populations.
C. Bison in current populations are less able to
interbreed with other species.
D. The current bison populations are less likely to
be able to adapt to environmental changes.
Bison have come close to extinction due to
uncontrolled hunting, drought, and disease. There is
now very little genetic variation in bison populations.
Which of the following is a result of the limited
genetic variation in the current bison populations
compared to earlier bison populations with more
variation?
A. Bison in current populations are more resistant
to new diseases.
B. The survival rate of young bison has increased
in current populations.
C. Bison in current populations are less able to
interbreed with other species.
D. The current bison populations are less likely to
be able to adapt to environmental changes.