Download speciation

MECHANISMS OF
EVOLUTION
species diversify (change)
when they are introduced to
habitats, environments, niches
or selection pressures
SPECIATION
• The creation of new species as a
result of selection pressures
Species – can interbreed &
produce fertile offspring
1. Species A migrates from the
mainland to the first island.
2. Isolated from the mainland, species A
evolves to species B.
3. Species B migrates to the second
island.
4. Species B evolves into species C.
5. Species C re-colonizes the first
islands, unable to reproduce with
species B.
6. Species C migrates to the third
island.
7. Species C evolves into species D.
8. Species D migrates to the first and
second island.
9. Species D evolves to species E.
This process could go on indefinitely until
a large diversity is reached.
ADAPTIVE RADIATION
• process of evolution of one species
into an array of different species that
occupy different niches
examples:
• Hawaiian Finches, Galapagos Finches, Marsupials
DIVERGENT EVOLUTION
• pattern of evolution in which species
that were once similar become more
and more distinct
examples
Allopatric Speciation
Sympatric Speciation
Geographic Isolation
Reproductive Isolation
Geographic Isolation
• physical barriers that prevent species from
interbreeding and reproducing
examples
Grand Canyon, Lakes that Dry Up
Deforestation, River Formation,
Mountain Ranges, Lava Flows
Allopatric Speciation
• Form of divergent evolution when species
are separated by physical barriers
South Rim –
Albert Squirrel
North Rim –
Kaibab Squirrel
Sympatric Speciation
• form of divergent evolution without a
physical barrier
Desert Kit Fox
Red Fox
Reproductive Isolation
• once interbreeding species can no longer
produce fertile offspring due to speciation
(caused by geographic isolation, sympatric speciation, allopatric speciation)
Wood Frog
Leopard Frog
CONVERGENT EVOLUTION
• unrelated or distantly related
organisms that have evolved
similar characteristics
examples
streamlined body of fish,
whales, dolphins
wings of bats, birds, insects
They may look similar, but it's not because they're close relatives. Instead,
they've evolved similar adaptations because they occupy similar niches -dining on ants, hunting in the high grass, or swimming in the dark –
although their evolutionary origins are quite different.
Darwin would say…
“unrelated organisms have evolved similar
variations or adaptations because they
occupy similar environments and face the
similar selection pressures”
“those adaptations provide an increased
fitness for that organisms”
Analogous Structures
TEMPO = Rates of Speciation
Gradualism vs. Punctuated Equilibrium
GRADUALISM
• idea that species originate through gradual
buildup of new adaptation and variations
-baby steps-
-slow change over time
PUNCTUATED EQUILIBRIUM
• speciation occurs in rapid bursts
• long periods of stability without change
• change only occurs when there is an immediate
selection pressure
(climate, predation, competition, geological event)