EESA01H3 Lecture Notes - Denitrification, Metapopulation, Heterotroph

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25 Jan 2013
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Earth’s Environmental Systems
Our planet’s environment consists of complex
networks of interlinked systems.
Earth uses cycles that shape the landscapes around
us and guide the flow of key chemical elements and
compounds that support life and regulate climate.
Systems show several defining properties
System is a network of relationships among parts,
elements, or components that interact with and
influence one another through the exchange of
energy, matter, or information.
Open Systems are systems that receive input of both
energy and matter and produce outputs of both
Closed Systems receive inputs and produce outputs
of energy, but not matter.
o in nature, no system is perfectly closed
Energy inputs to the earth’s environmental systems
include
o Solar radiation
o Heat released by geothermal(地热) activity
o Organismal metabolism(生物体的新陈代谢)
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o Human activities (eg. Fossil fuel combustion)
Information energy can come in the form of sensory
cues from:
o visual signs
o Olfactory (chemical) signs 嗅觉
o Magnetic signs 磁迹象
o Thermal signs 热的迹象
Inputs of matter occur when chemicals or physical
material moves among systems
o Eg. Seeds being dispered long distances
o Migratory animals 迁徙动物 deposit waste far
from where they consumed food
Eg. Gulf of St. Lawrence receives inputs from the St.
Lawrence, fishers harvest some of the systems
output: matter and energy in the form of fish and
plankton. 浮游生物
o Output becomes input to the human economic
system and to the digestive systems 消化系统 of
the people who consumer seafood from the St.
Lawrence
Sometimes a system’s output can serve as input to
that same system
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o This is a circular process known as feedback
loop
Can be positive or negative
In a negative feedback loop output
that results from a system moving in
one direction acts as input that moves
the system in the other direction,
o Input and output essentially
neutralize each other
o EG. Thermostat working to
stabilize rooms temperature
o EG. Our bodies, when we get too
hot, our sweat glands pumpe out
moisture that evaporates to cool
us down.
Most systems in nature
involve negative feedback
loops.
Positive feedback loops have the
opposite effect, rather than stabilizing
a system, they drive it further toward
one extreme or another.
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