Download What was Darwin`s explanation for evolution?

Aim: How does geographic &
reproductive isolation lead to
speciation?
HW: January 2014 # 56-63
Evolution has lead to
the formation of new
Speciation
species(__________)
from different ancient
organisms.
Species- a group of organisms
that share certain characteristics
& can mate with one another,
producing fertile offspring.
What was Darwin’s
explanation for evolution?
NATURAL
SELECTION
HOW DOES EVOLUTION
REALLY WORK?
http://www.pbs.org/wgbh/evolution/educators/teac
hstuds/svideos.html
Natural Selection
•According to
Darwin nature
controls evolution
•The environment
selects the
characteristics best
suited for survival
in a particular area.
Geographic Isolation
•The idea that two populations of the same
species of organism can evolve separately
because of a geographic barrier.
Physical barriers
–Mountains
–Bodies of water
–lakes
How does Geographic isolation
lead to Speciation?
Those who have an adaptive variation
will survive & reproduce in the
different environments. This leads to
different species with different
variations.
Darwin’s Finches (An Example
of Geographic Isolation)
All came from a common ancestor &
due to different environments on each
island, new species evolved that were
adapted to their particular
environment.
Evolution of many species
from one common
ancestor due to natural
selection
Each group of finches adapted to
its new environment, and through
the process of natural selection,
became different enough that
interbreeding became impossible.
Reproductive Isolation:
A reproductive barrier keeps similar
species from interbreeding.
EX.
1) Timing- two similar species may have
different breeding seasons.
2) Behavior- two similar species may have
different courtship or mating behaviors.
How long does evolution take?
Evolution takes a long time, but if the
environment changes suddenly,
evolution will be faster