Energy

Question 1

Ecosystem, Standing crop and biomass definition

Answer 1

• Ecosystem: Biological community together with the abiotic environment in which it is set
• Standing crop: The bodies of living organisms within a unit area
• Biomass: Mass of organisms per unit area of ground (or water)
  Usually expressed as units of energy (e.g. joules/m2)

Question 2

What is the first law of thermodynamics?

Answer 2

• Energy cannot be created or destroyed; it can change from one form to another
  e.g. Organisms must capture energy from another source to survive

Question 3

What is the second law of thermodynamics?

Answer 3

• When energy is converted from one form to another some of it is lost in form of heat and entropy increases
  E.g. when energy is transformed in the form of food a portion of it is in living tissue but a large part of it is dissipated as heat

Question 4

What is primary productivity?

Answer 4

• Flow of energy through a terrestrial ecosystem starts with the harnessing of sunlight by autotrophs
• Rate at which light energy is converted by photosynthesis to biomass/area

Question 5

Photosynthesis

Answer 5

• Energy from the sun is transformed into chemical energy of sugar molecules
  6 CO2 + 12 H2O + radiant energy
  C6H12O6 + 6 H2O + 6 O2

Question 6

Primary productivity: Chemosynthesis

Answer 6

• Lithotrophs use inorganic substrates as energy
• Bacteria or Archaea
• Often extremophiles
• Important in the formation of soil

Question 7

What is Gross Primary Productivity (GPP)?

Answer 7

• Total amount of energy that plants capture and assimilate in a given period of time [total rate of photosynthesis]

Question 8

What is Net Primary Productivity (NPP)?

Answer 8

• Plant growth per unit area per time
• Represents the rate of production of new biomass
  NPP = GPP – cellular respiration (R)
• Only NPP is available as food to organisms

Question 9

Primary productivity: Cellular respiration

Answer 9

• Chemical energy captured in photosynthesis is released within cells of plants and animals
  C6H12O6 + 6 H2O + 6 O2
  6 CO2 + 12 H2O + energy
• This energy is then used for biological work
  e.g Creating new cells

Question 10

What influences primary productivity?

Answer 10

• Water
• Temperature
• Nutrient availability
• Climate

Question 11

Food chain and trophic level order

Answer 11

1. Producers
2. Primary consumers
3. Secondary consumers
4. Tertiary consumers
5. Decomposers
   - Less energy is available for each trophic level bc is lost by respiration and excretion
   - 10% of assimilated energy pass between trophic levels
   - % energy transferred from one trophic level to another is ecological efficiency

Question 12

What is the equation for food web complexity

Answer 12

Connectance = actual number of inter-specific interactions/ potential number of inter-specific interactions

• If there are ‘n’ species - then the potential number of interactions is
  = (n)(n-1) / 2

(Assuming a species doesn’t exhibit cannibalism)

Question 13

What is a Trophic Cascade?

Answer 13

• Change in food web, especially at top can strongly affect
  ecosystem more widely Trophic cascades
• Example: Wolves in Yellowstone (Keystone spp)

Question 14

Food webs

Answer 14

• Food webs = graphical depiction of the interconnections among species based on feeding relationships.
• Food webs are dynamic
• Resources fluctuate in abundance - animals and plants
• Seasonal (temporal) change can profoundly affect the diet available to a predator