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?2
NATURAL
SELECTION
HOW DOES
EVOLUTION REALLY
WORK?
http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html
Natural Selection2
According to Darwin,
nature controls evolution,
the environment selects
the characteristics best
suited for survival in a
particular area.
Geographic Isolation3
•When part of a population of a species
becomes geographically isolated from
the remainder, it may (over time)
evolve characteristics different from
–Physical barriers
the original population.
•Mountain Ranges
•Large bodies of water
•Deserts
•Great Wall of China
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)5
All came from a common ancestor.
Due to different environments on
each island, new species evolved
that were adapted to their particular
environment
Adaptive Radiation6
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:7
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?8
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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