1.3 energy and equilibria

Question 1

1st law of thermodynamics

Answer 1

• energy can neither be created nor destroyed
• total amount of energy in an isolated system will not change, but it can transform type

Question 2

1st law of thermodynamics in food chains

Answer 2

• energy enters system as light
• transformed into chemical energy during photosynthesis
• eaten and then converted into mechanical energy
• energy lost as heat

Question 3

implications of the 1st law

Answer 3

• energy will never increase once entered, needs energy to keep entering to function
• can’t create energy to use, only transform available energy
• no new energy is being created

Question 4

2nd law of thermodynamics

Answer 4

• the entropy of a system increases over time
• an increase in entropy = a decline in the amount of available energy

Question 5

2nd law of thermodynamics in food chains

Answer 5

• light energy is most useful as it’s low entropy, used for photosynthesis
• however use of chemical energy is inefficient, lost as heat
• as energy changes form, less concentrated, less available to work

Question 6

implications of the 2nd law

Answer 6

• entropy will always increase so there must be a continuous input of energy
• entropy is reduced by an input of energy

Question 7

negative feedback loop

Answer 7

• returns the system to equilibrium

Question 8

predator prey relationship

Answer 8

• example of negative feedback loop
• increase in prey population gives more food for predators
• increased predator population increased predation and prey population falls
• less prey means predator populations decrease
• less predators prey populations increase
  cycle repeats

Question 9

positive feedback loop

Answer 9

• amplifies the change in the system

Question 10

climate change
positive feedback loop

Answer 10

• more co2 in the atmosphere increases temperatures
• permafrost melts releasing methane
• methane (GHG) goes into the atmosphere increasing temperatures

Question 11

tipping points

Answer 11

• pushes the system to a new state of equilibrium

Question 12

problems with tipping points reached

Answer 12

• environmental support systems could collapse
• food production capacity will decrease
• climate may become unsuitable for human existence

Question 13

india case study
feedback loop

Answer 13

• tree branches cut for fuel to cook
• population increased, people need to walk further to get branches
• children tasked, children asset
• population increased further
• tipping point was reached
• cow dung was used instead, unavailable as fertilizer
• decreased soil fertility, drop in food production
• technocentric solution
• introduction of biodigesters, breaks down organic waste into methane gas
• leftover organic waste used for fertilizer
• no longer need to cut down tree branches, reversed impacts

Question 14

steady state equilibrium

Answer 14

• many small changes over time
• countered by negative feedback loops and brought back to the same state as before

Question 15

stability

Answer 15

• ability of an ecosystem to remain in balance

Question 16

resistance

Answer 16

• when an ecosystem continues to function during a disturbance
• negative feedback to maintain the system in a steady state during a disturbance
• normal patterns continue regardless of the disturbance

Question 17

resilience

Answer 17

• ability of an ecosystem to recover after a disturbance
• negative feedback returning the system to a steady state after a disturbance
• normal patterns are restored after the disturbance

Question 18

disturbances

Answer 18

• flooding, fires, volcanic eruptions
• deforestation, pesticides, introduced species

Question 19

stability
climate and limiting factors

Answer 19

• equable climate, few limiting factors will be more stable

Question 20

stability
biodiversity

Answer 20

• higher biodiversity ensures complexity
• if one part of the system collapses it can be supported by another part
• species disappears, their niche can be taken over by another species

Question 21

stability
trophic complexity

Answer 21

• many trophic levels complexify food webs supporting greater biodiversity

Question 22

stability
nutrient stores

Answer 22

• size, distribution of nutrient stores
• rate of nutrient cycling
• if all nutrients are held in a single store and it is destroyed, the system can collapse

Question 23

stability
frequency and intensity of disturbances

Answer 23

• small, infrequent disturbances can be tolerated and overcome
• large, frequent causes problems

Question 24

case study
temperate grasslands: north american prairies

Answer 24

• fertile soil, biggest store in the nutrient cycle
• fire is part of the natural cycle, releases nutrients, balancing the cycle
• the system is resilient
• cleared natural grasses with cultivated ones
• crops remove the nutrients from the soil but are then taken away from the system so it isn’t replenished
• herbicides and pesticides used to kill, reduced biodiversity
• most animals removed so no addition of nutrients
• any fertilizers added only replace nutrients not organic content
• tipping point reached in the 1930s with the dust bowl
• decades to restore soil fertility and productivity

Question 25

case study
tropical rainforest: madagascar

Answer 25

• majority of nutrients in biomass
• high biodiversity
• resilient to small scale damage
• exploitation of the rainforest for wood, mineral wealth, farming

after large area cleared:
- nutrients removed, little regrowth
- heavy rainfall washes away leaf litter
- soil is exposed and washed away
- loss of trees, water recycling (transpiration) reduced
- loss of biodiversity, removal of vegetation removes food source and habitat