Download Development of New Species by Evolution What is Speciation?

Development of New Species
by Evolution
What is Speciation?
• Speciation is the
evolution of 1+
species from a single
ancestor species.
• It can occur when
members of a population
become isolated from each
other.
• Once two populations are
reproductively isolated,
they are considered
separate species.
Allopatric Speciation
(Geographic Isolation)
• A physical barrier
(continental split, rise in
sea level, formation of
mountain range, advance
of glacier, change in
habitat) prevents gene
flow between
populations of a species
Sympatric Speciation
• A process through
which new species
evolve from a single
ancestral species
while inhabiting the
same geographic
region.
Behavioral Isolation
• Two populations are
capable of
interbreeding, but have
differences in courtship
rituals or other
reproductive strategies.
Temporal Isolation
• Species reproduce at
different times.
Speciation in Darwin’s Finches
• Speciation in the Galapagos
finches occurred by:
1. Founding of a new population
2. Geographic isolation
3. Changes in new population’s
gene pool
4. Reproductive isolation
5. Ecological competition
Evolution does not occur in a set direction
• Evolution builds on what
already exists, so the more
variety there is, the more
there can be in the future.
• However, evolution does
not necessitate long-term
progress in a set direction.
Rate of Evolution
• Gradualism - theory
that new species evolve
as the genomes of two
populations differentiate
over time.
• Punctuated equilibrium theory that populations
remain genetically stable
for long period of time,
interrupted by brief
periods of genetic change.
Mechanisms of Evolution
• Divergent Evolution
- when isolated
populations of a
species evolve
independently.
• Convergent Evolution occurs when Natural Selection
has produced similar
adaptations in response to
similar environment between
different species.
Coevolution
• Species that interact closely
often adapt to one another
in a process called
coevolution.
Adaptive Radiation
Adaptive Radiation is
the evolution of many
diversely adapted species
from one common
ancestor.
It usually occurs on an
isolated island.
Ex. Darwin’s finches
Patterns of Evolution