Systems and models Flashcards
What is a system?
A system is an assemblage of parts, working together, forming a functional whole
What is a transfer?
Something moving from one place to another. It does not change its type (i.e. water flowing down a mountain)
What is a transformation?
When things change form (i.e. liquid to a gas)
When the inputs = outputs, the system is in …………
Equilibrium
What is an open system?
A system that exchanges energy and matter with its environment
What is a closed system?
A system that exchanges energy but NOT MATTER with its environment
What is an isolated system?
A system that exchanges neither energy nor matter with its environment
What is a model? Why do we use it? Give one example
A model is a simplified version of a real system. We use it to understand and predict how a system will work and change. One example is with the weather and using a model to predict it
State 3 ways energy may flow through a system as a transfer, with examples
- heat -> respiration
- electrical -> in pylon wires
- chemical -> food in your gut
Using a plant as an example system, name the inputs, output, energy and matter transfers, matter and energy transformation
inputs: water, sunlight, CO2
outputs: oxygen, glucose
matter and energy transfer: water, light and chemical energy
matter and energy transformation: photosynthesis, respiration
What is the first law of thermodynamics?
Energy is never created or destroyed, only changed from one form to another
What is the second law of thermodynamics?
Entropy in a system always increases
What is entropy?
A measure of chaos and disorder in a system
What is low grade energy, and give an example?
Energy we can not use
example: heat
If there are more steps in a system, what happens to the entropy?
It increases
Compare the energy efficiency of herbivores and carnivores (entropy)
Their entropy is the same, as they both lose energy in metabolic processes (running from a predator and predators running after prey)
Explain why heat is an example of energy characterised by high entropy?
Because high entropy means more chaos in a system, therefore there is more low-grade energy (heat) lost to the environment
What happens to entropy when a creature dies?
Entropy increases because all their energy is converted into heat (low-grade energy)
Explain why an organism ‘surviving against the odds’ goes against the second law of thermodynamics
An organism going ‘against the odds’ is going against high entropy so has a less chance of survival
Explain why the entropy of a living system stays low while the entropy of the environment increases
The environment is always gaining low-grade energy from other systems and organisms, therefore there is a high entropy, whereas a living system can replenish its energy
Explain why a high level of complexity in a food web is more likely to provide a stable system
As one organism goes, another organism can take its role, therefore there is more stability
What does a stable equilibrium graph look like?
The line returns to the original equilibrium after the disturbance
What does a static equilibrium graph look like?
There is no change or disturbance over time
What does an unstable equilibrium graph look like?
Returns to a new equilibrium after the disturbance
What does a steady-state equilibrium graph look like?
The system is more or less constant, but has small fluctuations
Describe the role of any 2 names historical influences in the environmental movement [3]
(remember a historical influence can be a person, organisation or event)
Some examples (only need 2):
- Greenpeace (1970) -
Took direct action to prevent whale killings
- Chernobyl nuclear meltdown (1986)
reinforced negative perception of nuclear power in society - Rachel Carson -her book: A silent spring
raised awareness on the threat of the pesticide DDT, as a POP, to organisms high up the food chain - Minimata disease -
Raised awareness on the regulation of effluents from factories and increased legislation
What is feedback?
Feedback occurs when the output of a system influences the inputs and hence affects the state of the system
What is positive feedback? is it usually a good or bad thing?
positive feedback changes a system to a new state. It is usually a bad thing
What is negative feedback? is it usually a good or bad thing?
negative feedback returns a system to its original state. It is usually a good thing
Give 2 examples of positive feedback
- Arctic ice melts reducing albedo [1] less incoming solar radiation is reflected [1] and this increases further melting of Arctic ice [1].
- Increased temperatures result in greater evaporation [1] more water vapour in the atmosphere acting as a greenhouse gas [1] leads to increased temperature [1].
Give 2 examples of negative feedback
- CO2 levels rise, meaning the temperature of the earth rises. As the earth warms, the rate of photosynthesis increases, therefore more CO2 is removed from the atmosphere, reducing global temperatures
- As the Earth warms, there are higher rates of evaporation. This produces more clouds. Clouds increase albedo, reflecting more light away from the earth. The temperature falls and evaporation rates fall
What is albedo?
The reflectiveness of the Earth’s surface
What is anoxic?
lack or without oxygen
What is meant by ‘Resilience’?
The ability of a system to ‘bounce back’ after a disturbance
What is meant by ‘tipping point’?
When a system is pushed past a point, where it cannot return to its original state, even if the main cause is removed