1.3 Energy and Equilibrium

Question 1

1st Law of Thermodynamics

Answer 1

Energy in an isolated system and is neither created nor destroyed, only changes forms.

Question 2

2nd Law of Thermodynamics

Answer 2

the entropy of an isolated system, not in equilibrium, will tend to increase over time. this reduces amount available to do work.

Question 3

Entropy Definition

Answer 3

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.

Question 4

Entropy explanation

Answer 4

Increase of entropy from energy transformations = Reduces energy available to do work

Question 5

1st Law of Thermodynamics represented in a Food Chain + Energy Production System

Answer 5

Solar energy → absorbed by plants → made into chemical energy → plants eaten by animals & used for energy

Question 6

2nd Law of Thermodynamics represented in a Food Chain + Energy Production System

Answer 6

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

Question 7

steady state equilibirum

Answer 7

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

Question 8

Stable equilibrium definition

Answer 8

The tendency in a system for it to return to a previous equilibrium condition following disturbance.

Question 9

Static equilibrium definition

Answer 9

Occurs when there is no change over time.

When it is disturbed, it either returns to equilibrium (stable) or adopts a new equilibrium (unstable)

Question 10

Resilience definition + explanation

Answer 10

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.

Question 11

Factors that can increase resilience (8)

Answer 11

• higher temps, light+water availability, resulting in faster growth rates: tropical rain forest
• greater genetic diversity
• greater species diversity
• reduce an invasive species
• less pollution
• faster rate of reproduction (r-strategist)
• large ecosystem
• spread over a large geographical energy

Question 12

Tipping points definition

Answer 12

a critical threshold when even a small change can have dramatic effects and cause a disproportionately large response in the overall system.

Question 13

Tipping points real life example

Answer 13

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

Question 14

Negative feedback loop definition

Answer 14

feedback that tends to counteract any deviation from equilibrium and promotes stability.

Question 15

Negative feedback loop example

Answer 15

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

Question 16

Positive feedback loop definition

Answer 16

feedback that increases change; it promotes deviation away from equilibrium.

‘Vicious cycle’ ↔ disequilibrium

Question 17

Positive feedback loop example

Answer 17

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.

Question 18

Albedo definition

Answer 18

The amount of light reflected by a surface.

Question 19

Systems at threat from tipping points

Answer 19

• Antarctic sea ecosystem
• Amazon Rainforest
• Greenland ice sheet

Question 20

POSITIVE Human Impact on Resilience of Systems

Answer 20

Humans can remove or mitigate threats to the system (pollution, invasive species) — resulting in faster recovery/more resilience

Question 21

NEGATIVE Human Impact on Resilience of Systems

Answer 21

• 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.
• Climate change: Over-abstraction of surface water worsens the problems of extreme weather (e.g., drought) caused by climate change.

Question 22

Delays in Feedback Loops real life example

Answer 22

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

Question 23

Equilibirum

Answer 23

A state of balance among the components of a system.

Question 24

Unstable equilibrium

Answer 24

The tendency in a system to adopt a new equilibrium following disturbance.

Question 25

how do food chains show the 2nd law of thermodynamics?

Answer 25

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.

Question 26

the implications of the laws of thermodynamics to ecological systems

Answer 26

• 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