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Energy Flows in the Ecosphere
Introduction
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Most energy on Earth derives from
the radiant energy of the sun
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This radiant energy is transformed
into chemical energy (energy stored
in the chemical bonds of molecules)
and mechanical energy (energy due
the motion – kinetic energy - or
position of an object – potential
energy)
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It is important to understand how
energy links species, and flows
through ecosystems because
changing the energy available at
one part of the food chain causes
changes throughout the ecosystem
Energy
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Energy is the capacity to do work and is measured
in calories
A calorie is the amount of heat needed to raise one
gram (one millilitre) of water one degree Celsius (C),
starting at 15 degrees
Potential energy is stored energy that is available
for later use (e.g., gasoline)
Energy derived from an object’s motion and mass is
known as kinetic energy (e.g., engine using gas)
Energy

Most of the energy available for use is called lowquality energy
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The total energy of all moving atoms is referred to as
heat, a low-quality energy
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diffuse, dispersed at low temperatures, difficult to gather
vs. temperature, a measure of average speed of molecules
or atoms in a substance at a particular time
High quality energy, such as coal or gasoline, is
easy to use, but the energy disperses quickly
Energy type should be matched to use to maximize
efficiency
Energy

It is important to match quality of energy supply
to the task at hand – not to use high quality
energy (e.g. non-renewable resources) for
tasks that can be done with low quality
supplies (e.g. renewable resources)

All organisms require energy for growth tissue
replacement, movement, and reproduction
Energy
Energy
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Solar cells in a
remote village of
Thailand
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High-quality energy
or low-quality
energy source?
Energy
Laws of Thermodynamics
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Two laws of physics describe the way in which
energy transformations take place all over the world;
there are trillions of transformations per second
The first law is the law of conservation of energy
 energy can neither be created nor destroyed; it is
merely changed from one form into another
 The total amount of energy in the universe is
constant
Energy
Laws of Thermodynamics
The
second law of thermodynamics (law of entropy) tells us
that when energy is transformed from one form into another, there
is always a decrease in the quality of usable energy; some energy
is ‘lost’ as lower-quality, dispersed energy to the surrounding
environment, often as heat
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Entropy is a measure of the disorder or randomness of a system.
High-quality, useful energy has low entropy
Organisms must continually expend energy to maintain
themselves – whenever used, some is lost creating the need for
an ongoing supply
Also tells us energy cannot be recycled, it flows – as it flows
through a system it is constantly degraded – the more it is
transformed, the more it is dispersed becoming less useful
Energy
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Many environmental problems are a result of
increased entropy
Some of the principal transformations that
have to take place to achieve a sustainable
society are
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to view high energy consumption as undesirable
to reduce energy waste
to switch from the non-renewable sources of
energy that now dominate (coal and oil
particularly) to renewable sources
Discussion Question
Using the laws of thermodynamics, explain
why energy conservation is necessary to
achieve a sustainable society – that is, a
society that can meet human needs and
address environmental problems both now
and it the future