1.3: energy & equilibria Flashcards
1st law of thermodynamics:
energy is neither created nor destroyed
this means that the total energy in any isolated system, such as the entire universe is constant. all that can happen is the form the energy takes changes. The first law is often called the principle of conservation of energy.
2nd law of thermodynamics:
the entropy of an isolated system not in equilibrium will tend to increase over time.
energy goes from a concentrated form to a dispersed form.
entropy:
measure of the amount of disorder in a system. it refers to the spreading out or dispersal of energy.
- more entropy = less order
- over time, all differences in the universe will be evened out until nothing can change.
- when energy conversions take place, they are never 100% efficient and some energy is wasted as heat energy
- an increase in entropy arising from energy transformations reduces the energy available to do work
calculating the % of energy transferred -
- divide energy from the second trophic level by the energy from the first trophic level
- multiply by 100
equilibrium:
the tendency of the system to return to an original state following disturbance. it is a state of balance in an ecosystem.
steady state equilibrium
a characteristic of open systems where there are continuous inputs and outputs of energy and matter, but the system as a whole remains in a more-or-less constant state.
negative feedback stabilises steady state equilibria. it tends to damp down, neutralise, or counteract any deviation from an equilibrium. thus, resulting in the self-regulation of a system.
no long-term changes but there may be small fluctuations in the short term.
eg. water tank, in economics, a market may be stable but there are flows of capital in and out of the market
static equilibrium:
Static equilibrium – there is no change over time. When a static equilibrium is disturbed, it will adopt a new equilibrium as a result of the disturbance. It is always in balance. Most non-living systems like a pile of rocks or a building are in a state of static equilibrium.
systems can also be stable or unstable:
in a stable equilibrium - the system tends to return to the same equilibrium after a disturbance
in an unstable equilibrium - the system returns to a new equilibrium after a disturbance
feedback loop:
when information that starts a reaction in turn may input more information which may start another reaction.
ecosystems are said to be “self-regulating”; they contain feedback mechanisms which function to maintain the system in its state of equilibrium
positive & negative feedback:
positive: (temperature and greenhouse gases)
- change a system to a new state (amplifies change)
- destabilising as they increase change (deviation from stability)
negative: (eg. predator-prey relationships)
- return it to its original state
- stabilizing as they reduce change
are positive & negative feedback loops stabilising or destabilising?
negative feedback loops - stabilising and occur when the output of a process inhibits or reverses the operation of the same process in such a way to reduce change- it counteracts deviation.
positive feedback loops - destabilising and tend to amplify changes and drive the system towards a tipping point where a new equilibrium is adopted. positive feedback results in a ‘vicious cycle’.
resilience:
the capacity of a system to respond to a disturbance. the more resilient a system, the more disturbance it can deal with. it is the ability of a system to return to its initial state after a disturbance. if it has low resilience, it will enter a new state.
factors affecting ecosystem resilience -
- more diverse and complex an ecosystem = more resilient, since there are more interactions between species.
- greater the genetic diversity within a species, the greater the resilience.
- species that can shift their geographical ranges are more resilient
- climate affects resilience. in tropical rainforests, growth rates are fast since water, light and temperature are not limiting.
- faster the rate of reproduction of a species, means the recovery rate is faster
- larger the ecosystem is, more resilience as animals can find each other more easily and there is less edge-effect
- humans can remove or mitigate the threat to an ecosystem, and this will result in faster recovery
tipping points:
small changes occur in systems and may not make a huge difference. but when these changes tip the equilibrium over a threshold, known as a tipping point, the system may transform into a very different one.
positive feedback tends to amplify and drive a system towards a tipping point.
an ecological tipping point is reached when an ecosystem experiences a shift to a new state in which there are significant changes to its biodiversity and the services it provides.
