Download V. Speciation Notes

V. The Process of Speciation
Speciation – formation of a new
species.
Species – a group of organisms
that can breed with one
another & produce fertile
offspring.
*Members of a species can lose
the ability to interbreed due to
isolation.
Isolation – anything preventing
two groups within a species
from interbreeding.
A. Isolating Mechanisms
*As new species evolve, populations
become reproductively isolated from
each other.
Reproductive isolation – loss of two
groups’ ability to interbreed &
produce fertile offspring.
-Reproductive isolation can
develop through :
1. Behavioral isolation – when
two populations are capable
of interbreeding but have
differences in courtship
rituals/other reproductive
strategies that involve
behavior, ex :
Eastern & Western meadowlarks.
Geographic Isolation
2. Geographic isolation –
when two populations are
separated by geographic
barriers such as rivers,
mountains, or bodies of
water, ex : Abert squirrel
& Kaibab squirrel.
Temporal Isolation
3. Temporal isolation –
when two or more
species reproduce at
different times, ex :
rainforest orchids.
Processes of Change
*Species can also go through
the following processes of
change :
1. Divergent Evolution
2. Convergent Evolution
3. Coevolution
1. Divergent evolution – when
isolated populations of a
species evolve independently.
-Happens because of
geographic barriers or when a
small group leaves an original
population to colonize a new
area. Ex : Brown vs. Polar bears.
Convergent Evolution
2. Convergent evolution –
when natural selection
produces analogous
(similar) adaptations
in response to similar
environments, ex :
Serval cat (Africa)
& Maned wolf (SA) long ears/legs &
the same prey.
Coevolution
3. Coevolution – when two
or more populations that
closely interact over an
extended period of time
evolve together, ex :
flowers & bees.
B. Adaptive Radiation
Adaptive radiation – evolution of many diverse
species from 1 common ancestor, ex : Darwin’s
finches- spread.