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Energy and equilibria revision resource
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- The University Of York (UOY)
Energy and equilibria revision resource ESS Topic 1.3
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1.3 Energy and equilibria Key termsSignificant ideas: The first law of thermodynamics- is the principle of conservation of energy,
The first law of thermodynamics is the principle of conservation of energy, which states that which states that energy in an isolated system can be transformed, but
energy is an isolated system can be transformed but cannot be created or destroyed. cannot be created or destroyed.
The principle of conservation of energy can be modelled by the energy transformations along The second law of thermodynamics- refers to the fact that energy is
food chains and energy production systems. transferred through energy transfers. Entropy is a measure of the amount of
The second law of thermodynamics states that the entropy of a system increases over time. disorder in a system. An increase in entropy arising from energy
Entropy is a measure of the amount of disorder in a system. An increase in entropy arising from transformations reduces the energy available to do work.
energy transformations reduces the energy available to do work. Entropy- is a measure of the amount of disorder in a system.
The second law of thermodynamics explains the inefficiency and decrease in available energy Efficiency- useful energy, the work or output produced by a process divided
along a food chain and energy generation systems.. by the amount of energy consumed being input to the process:
An open system, an ecosystem, will normally exist in a stable equilibrium, either steady- state or Efficiency= work or energy produced/ energy consumed
one developing over time (e.g. succession), and maintained by stabilizing negative feedback Efficiency= useful output/ input
loops. Multiply by 100% if expressing efficiency as a percentage.
Negative feedback loops (stabalising) occur when the output of a process inhibits or reserves the Feedback loops- is when information that starts a reaction in turn may input
operations of the same process in such way to reduce change- it counteracts deviation. more information which may start another reaction.
Positive feedback loops- ( destabalising) will tend to amplify changes and drive the system toward Negative feedback loops- are stabalising and occur when the output of a
a tipping point where a new equilibrium is adopted. process inhibits or reverses the operation of the same process in such a way
The resilience of a system, ecological or social, refers to its tendency to avoid such tipping points to reduce change- it counteracts deviation.
and maintain stability. Positive feedback loops- are destabalising and will tend to amplify changes
Diversity and the size of storages within systems can contribute to their resilience and affect the and drive the system towards a tipping point where a new equilibrium is
speed of response to change. adopted.
Humans can affect the resistance of systems through reducing these storages and diversity. Steady state equilibrium- is a characteristic of open systems where there are
The delays involved in feedback loops make it difficult to predict tipping points and add to the continuous inputs and outputs of energy and matter, but the system as a
complexity of modelling systems. whole remains in more or less a constant state.
Energy in systems Efficiency- entropy
According to the first law of thermodynamics, Energy= work+ heat
ebergy is any isolated system is consistent and can The useful energy consumed by one trophic level is less than the total energy at the level below.
neither be created or destroyed. All that changes is Depending on the type of plant, the efficiency at converting solar energy to stored sugar is around 1-2%.
the form the energy takes. E.g.: Herbivores on average only assimilate (turn into animal matter) about 10% of the total plant energy they consume. The rest
In a power station, a form of energy (coal, oil, is lost in metabolic processes and escaping from the carnivore. This changes the stored chemical energy into work (running).
water etc.) is converted and transformed into But during its attempted escape some of the stored energy is converted to heat and lost from the food chain.
electricity. A carnivore’s efficiency is also around 105. As with the herbivore they matablolise stored chemical energy, in this case trying
The second law of thermodynamics states the to catch the herbivore.
entropy of an isolated system not in equilibrium As energy is dispersed intot he environment, there will laways be a reduction in the amount of energy passed on the next
will increase over time. tropic level.
More entropy+ less order That means the carnivore’s total efficiency in the chain is 0.02x0.1x0.1=0.0002%
When energy is used to do work, some This means that the carnivore loses most of its energy as heat in to the surrounding environment.
energy will be dissipated to the environment,
so energy efficiency is never 100%.
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