1.3 Energy and Equilibrium Flashcards
1st Law of Thermodynamics
Energy in an isolated system and is neither created nor destroyed, only changes forms.
2nd Law of Thermodynamics
the entropy of an isolated system, not in equilibrium, will tend to increase over time.
Entropy Definition
The measure of disorder in a system.
Entropy is simply a quantitive measure of what the 2nd law describes: dispersal of energy in a process of our material world.
Entropy explanation
Increase of entropy from energy transformations = Reduces energy available to do work
1st Law of Thermodynamics represented in a Food Chain + Energy Production System
Solar energy → absorbed by plants → made into chemical energy → plants eaten by animals & used for energy
2nd Law of Thermodynamics represented in a Food Chain + Energy Production System
When one animal feeds off another → loss of heat (energy) in respiration and movement
More and more energy is lost as one moves up trophic levels
Inefficiency/decrease in available energy along the food chain
steady state equilibirum
the condition of an open system, where there are no changes over the long term but in which there may be small oscillations in the very short term
Stable equilibrium definition
The tendency in a system for it to return to a previous equilibrium condition following disturbance.
Static equilibrium definition
Occurs when there is no change over time.
When it is disturbed, it either returns to equilibrium (stable) or adopts a new equilibrium (unstable)
Resilience definition + explanation
The ability of a system to return to its initial state after how a system responds to a disturbance.
The MORE resilient a system → the MORE disturbance it can deal with
e.g. in agriculture, we want stability so we can predict that the amount of food we grow is about the same each year. If this does not happen, it can lead to famine.
Factors that can increase resilience (8)
- high biodiversity (more species interactions -> if one species dies out the other takes its place)
- high genetic diversity
- species with geographical diversity (more migration routes = better able to survive enviornmental changes)
- large ecosystems (less edge effect= species can move around and adapt)
- faster reproductive rates -> can recover faster
human action:
- less pollution
- removal of invasive species
Tipping points definition
a critical threshold when even a small change can have dramatic effects and cause a disproportionately large response in the overall system.
Tipping points real life example
River Eutrophication
- rain washes fertilisers from farmers fields into rivers
- extra nutrients result in excessive plants growth
- light is blocked by decomposing plant material
- oxygen levels fall + animals die
- river becomes eutrophic + takes great effort to restore
Negative feedback loop definition
feedback that tends to counteract any deviation from equilibrium and promotes stability.
Negative feedback loop example
Predator-Prey model
- When prey populations (hare) increases, there is more food for predators (lynx) so they eat+breed more predators which eat more prey so that prey numbers decrease
Positive feedback loop definition
feedback that increases change; it promotes deviation away from equilibrium.
‘Vicious cycle’ ↔ disequilibrium
Positive feedback loop example
Global Temperatures rise, causing ice caps to melt. Dark soil is exposed, so more solar radiation is absorbed → reduces albedo of Earth so global temperatures rise + cycle keeps going.
Albedo definition
The amount of light reflected by a surface.
Systems at threat from tipping points
- Antarctic sea ecosystem
- Amazon Rainforest
- Greenland ice sheet
POSITIVE Human Impact on Resilience of Systems
Humans can remove or mitigate threats to the system (pollution, invasive species) — resulting in faster recovery/more resilience
NEGATIVE Human Impact on Resilience of Systems
- Reducing diversity: Hunting animals for pets, e.g., removal of fish from the tropical reefs.
- Reducing the size of the storages: Deforestation of tropical rainforests in Indonesia.
Delays in Feedback Loops real life example
Activities in one part of the globe may lead to a system reaching a tipping point elsewhere on the planet (e.g. the burning of fossil fuels by industrialised countries is leading to global warming, which is pushing the Amazon basin towards a tipping point of desertification) - continued monitoring, research and scientific communication is required to identity these links
Equilibirum
A state of balance among the components of a system.
Unstable equilibrium
The tendency in a system to adopt a new equilibrium following disturbance.
how do food chains show the 2nd law of thermodynamics?
Food chains show an increase in entropy.
- Low entropy light energy enters the food chain during photosynthesis.
- Light energy is used to break the chemical bonds of H2O and CO2 and reform them into carbohydrates.
- This chemical energy has higher entropy than light energy.
- The chemical bonds of the carbohydrates are broken to release the energy for use by the animals in life processes.
- This energy is dissipated as heat – which has very high entropy.
the implications of the laws of thermodynamics to ecological systems
- energy flows through ecosystems. energy enters as sunlight energy and is converted to new biomass and heat
- the energy entering the system equals the energy leaving it (first law)
- energy is inefficiently moved through food chains in the process of respiration and production of heat energy (second law)
- initial absorption and transfer of energy by producers is also inefficient due to reflection, transmission, light of the wrong wavelength and inefficient transfer of energy in photosynthesis (second law)
- light energy starts the food chain but is then transferred from producer to consumer as chemical energy
- as a result of the inefficient transfer of energy, food chains tend to be short
When is resilience good?
- ecosystems recovering after a disturbance (eg. fire, drought)
- forests regrowing after logging or fire
When is resilience bad?
- pathogens (disease) being resistant
- invasive species outcompeting native species
- pests resistant to pesticides -> continuing to damage crops
