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Chapter 23

BIOLOGY 2F03 Chapter Notes - Chapter 23: Sea Surface Temperature, Walker Circulation, Atmospheric Circulation

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D R.Kajura

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Chapter 23 Global Ecology
Patterns of biological diversity change through time
Abiotic condition impose a significant pressure on the organism that live within a given location
This pressure can impact the fitness of an organism that live in the given location
Plate tectonics
Over deep geologic time the movement of tectonic plates has created the landscaped we see
now and destroyed many others that we never will
Atmosphere consist of different layers same with the physical structure of the earth
Earth has a solid inner layer surround by a fluid mantle and an outer crust
The lithosphere sits on the slow moving asthenosphere
Where the lithosphere breaks we observe faults
Lithosphere is arranged into 15 major plates which have change in size
Plates move over time and crash into each other, separating or subsiding which damages the
physical structure of earth’s surface
Continental drift first proposed in the early 1900s
The idea that earth was dynamic and not fixed challenged scientist until they proved it later
Ecologist should care about this cause tectonic movement and atmospheric cycles, influence the
past and current diversity and distribution of species on the planet
Extinction events
Estimated suggest that only 1% of the species ever to occupy the earth are currently extant but
we should be skeptical about this claim
Rate of extinction has varied greatly over time
There have been 5 mass extinctions over the last 550 million years each characterized with a
loss of 75% of the species prior to the event
Mass extinction
oCretaceous 65 mya
oPermian 250 mya
oOrdovician 443 mya
Mass extinction cause by periods or warming or cooling, asteroid impacts and volcanic activity
Extinction have a large effect on biodiversity though loss of species and periods of rapid
Adaptive radiation often was able to act on few species as much of the niche space was no
longer occupied
These extinction caused lots of changed to the chemistry of the plant which posed as a
challenge for remaining species
Tetrapods (4 footed animal) first to colonize land appeared mid Devonian 350 mya
Today there are 30 000 species of tetrapods
Ecological mode is the same thing as a niche
Biogeographical Barriers
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The physical arrangements of land and sea can facilitate, or inhibit dispersal of species from one
location to another
oIslands far from mainland should have lower immigration rates then islands near
Asa grey botanist and natural historian
oMost important observation was that there exists substantial geographic variation in the
diversity of trees in the forest region of the temperate zone
olatham and ricklefs explored this observation and found 95% of all temperate tree
families have at least 1 representative species in eastern Asia and only 3% of temperate
tree species do not occur in eastern Asia
Atmospheric Cycles: the southern and north Atlantic oscillations
2 of the most relevant system are the southern and north atlantic oscillations
tragic crop failure resulted in walker trying to predict rainfall using the asian monsoon
he found a reduced barometric pressure in the eastern pacific was accompanied by an increase
in barometric pressure in the western pacific this oscillation
they use the southern oscillation index determined by the barometric pressure in tahiti and
proposal that the gradient in sea surface temperature across the central pacific ocean produces
a large scale atmospheric circulation system that moves in the plane of the equator
air over warmer western pacific rises, flows eastward in the upper atmosphere and then sinks
over the eastern pacific
west-ward flowing air joins rising air of pacific - as this warms, the moist air rises
oknown as walker circulation
during mature phase of El Nino, sea surface is much warmer than the average barometric
pressure over the eastern pacific
storms bring increased precipitation to much of north and south America
periods of lower sea surface temperature and higher than average barometric pressure in the
eastern tropical pacific is called La Nina
During La Nina: pool of warm seawater moves far into the western Pacific
warm water combines with lower pressure and generates many storms
ola ninas bring drought to south and north America
During El Nino: northern united states, Canada, Alaska are much warmer than average
During La Nina: regions are colder than average
othis global climate system affects ecological systems around the globe
El Nino and marine populations
produces declines in coastal populations of anchovies and sardines and seabirds
produced by changes in pattern of sea surface temperatures and coastal circulation
upwelling is driven by the southeast trade winds, while offshore upwelling is driven by the east
winds of the walker circulation
with an el nino, easterly winds slacken and the pool of warm water in western pacific moves
during mature phases, warm surface water along the west coast shuts off upwelling
othis shuts off nutrient supply
olower nutrient supply = less food to consumers in coastal food web
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