Transcript What was Darwin`s explanation for evolution?

Aim: How does geographic &
reproductive isolation lead to
speciation?
Master and commander
Speciation
Evolution has lead to
the formation of new
species from different
ancient organisms.
Species- a group of organisms that
share certain characteristics & can
mate with one another, producing
fertile offspring.
Population- all the individuals of a
single species that live in a specific
area.
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
Movie: Elements of biology:
agents of evolution
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
Adaptive Radiation
Evolution of many species
from one common ancestor due
to natural selection
Adaptive Radiation
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.
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
Patterns Of Change
•
Species with SHORT reproductive cycles that
produce MANY offspring tend to evolve more
quickly than species with LONG life spans and
FEW offspring.
•
Types:
1) Gradualism – evolution occurs steadily
through time (Slow & Continuous) .
2) Punctuated Equilibrium- species stay the
same for long periods of time and then change
rapidly.
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