Download Continental Drift PP

Continental Drift & Speciation
Continental Drift
• Alfred Wegener
• In the 1930’s suggested
that continents were
(and are currently)
moving relative to each
other and that at some
time in the past they
were joined together
forming a super
continent Pangea
Continental Geography
• The eastern coast of
South America and
the western coast of
Africa appear to fit
nicely together like
pieces of a puzzle
Paleontology & Climate
• The ranges of fossil
plant and animal
specimens of similar
age appear to correlate
well across current
continental boundaries
• Tropical fossils exist in
Antarctic sediment
suggesting that this
continent has not
always existed in its
current location
Past Glacial Events
• Mapping of the
extent of glacial rock
remains on the
different continent
suggests particular
connections
between the
continents in the
past
Plate Tectonics
• Continental Drift was not taken seriously
by the geological community until a
mechanism that could explain the
movement of the continents could be
developed
Ruggedness of the Ocean
Floor
• Through development of sonar and
more extensive use of submarines a
picture of a rugged sea floor emerged
(previously it was thought that the
ocean floor was flat)
• In fact, the Earth’s largest feature is the
Mid-Atlantic Ridge running down the
middle of the Atlantic Ocean
Oceanic Ridges
• At ocean ridges new
crust arises from
magma within the
Earth forcing the
existing plate out
while a new border
for the plate is being
made
Magnetic Striping
• As new magma
cools magnetic
crystals within it line
up with the magnetic
poles of the Earth
• The north end facing
north and the south
end facing south
• As magma in the
Earth’s core circulates
“magnetic or polar
reversals” occur
• Our current north and
south flip such that the
magnetic crystal line up
opposite of what they
would be normally.
Oceanic Trenches
• Where two plates
come together one is
subducted under the
other forming a trench
• Tension builds up in
the plate laying on top
while heat may
generate magma
below (Mts &
Volcanoes)
• Mapping of the
distribution of
Earthquakes across
the globe correlates
well with places
were plates are
coming together
• http://pubs.usgs.gov/publications/text/
Information on Continental Drift and
Plate Tectonics
Speciation
• Process by which:
a) subpopulations of one species diverge
becoming adapted to different
environments and reproductively isolated
b) descendants of a species become adapted
to an environment different than the one
in which it was originally adapted
Allopatric Speciation
• Type of speciation in which the
subpopulations diverge because they
are ‘separated by a geographic barrier’
Reproductive Isolation
• Pre-Zygotic
Mechanisms
1) Temporal
2) Behavioral
3) Mechanical
4) Ecological
5) Gametic Mortality
• Post-Zygotic
Mechanisms
1) Hybrid Inviability
2) Hybrid Sterility
3) Low Fitness Hybrids