LAWS OF THERMODYNAMICS

1st. the law of conservation of energy - energy cannot be created or destroyed but only transformed or transferred

• modelled by energy transfers and transformations within system diagrams, food webs and food chains

• energy within an isolated system (e.g. the universe) is constant - amount does not change over time

2nd. the law of entropy - states that the entropy of a system increases over time

• entropy (def). measures the amount of disorder within a system

• disorder refers to the dispersal and loss of energy

• an increase in entropy increases the amount of energy lost in transfers and transformations - reducing the energy available for growth

• inefficiency increases as energy and biomass moves through trophic levels

• heat as a form of energy has a high amount of entropy, and is therefore a low quality form of energy

losses through food chains

STABILITY

feedback loops (def). ways in which systems respond to change, set into two categories

• negative feedback loops (def). counteracts deviation, usually to restore the system back to its original state - is a form of self regulation for the system

• e.g. rising global temperatures → icecaps melting → more available water → more clouds created → solar radiation reflected by clouds → temperatures fall

• positive feedback loops (def). builds on deviation and usually moves the system further away from its original state, causing in to pass a tipping point and establish a new state

• e.g. rising global temperatures → ice caps melt → exposed soil → absorbs more solar radiation → decrease in earth’s albedo → temperatures continue to rise

  • albedo (def). the reflecting ability of a surface or thing

equilibrium (def). the tendency of a system to return to its original state following a disturbance OR a state of balance between the components of a system

• steady state equilibrium (def). a characteristic specific to open systems where there are constant inputs and outputs but overall the system remains in a constant state where there are no large changes over time

  • achieved through negative feedback mechanisms

  • e.g. a water tank where an equal amount of water is flowing in as is flowing out - allowing a constant amount of water to be in the tank at all times

  • e.g. a population of ants where the birth and death rates are evenly matched, allowing a constant population size

e.g. human body temperature as a steady state equilibrium

• systems can have a stable or unstable equilibrium

• stable - tends to return to the same state after a disturbance - uses negative feedback loops

stable equilibrium

• unstable - tends to end up at a new equilibrium after a disturbance - uses positive feedback loops

unstable equilibrium

• static equilibrium (def). a system in which there is no change over time - when disturbed the system develops a new state or equilibrium

  • often seen in non-living systems - e.g. building or piles of inanimate objects

  • cannot occur in living systems - will always be transfers of energy and matter

resilience (def). refers to how well a system responds, recovers and returns to its equilibrium after a disturbance

• low resilience = new state

• high resilience = original state

factors of resilience :

• climate - colder climates will have slower growth rates - affecting the systems ability to recover from disturbance

• genetic diversity - species are able to replace others in case of disease or the extinction of one species

• area - larger area is likely to come with more biodiversity as well as more space for organisms - reducing need for disease and competition

• diversity and complexity - more interactions for the system to fall back on

tipping points (def). the point where an ecosystem shifts to a new state - involving noticeable changes in its organisms and what it can provide

• changes are long lasting and difficult to reverse

• are a result of positive feedback

• e.g. death of a coral reef OR extinction of a keystone species