Energy and Ecosystems

Question 1

what controls the distribution and abundance of organisms in a habitat?

Answer 1

• biotic factors, e.g. predators, disease
• abiotic factors, e.g. light intensity and temperature

Question 2

why is 90% of chemical food energy lost to surroundings?

Answer 2

• uneaten parts e.g. bones
• decay of dead material e.g. bacteria decaying material
• excretion e.g. energy lost in faeces
• exothermic reactions e.g. heat lost in respiration

Question 3

how can percentage efficiency be calculated of energy transfer (between organisms)?

Answer 3

energy out / energy in x100

Question 4

what is a bomb calorimeter used for?

Answer 4

• measuring biomass
• bomb calorimeter burns known dry mass in oxygen
• submerged in water and change in water temperature is used to calculate energy in sample

Question 5

what is net primary productivity?

Answer 5

• NPP
• chemical energy store in plant biomass after respiratory losses are taken into account

Question 6

what is gross primary productivity?

Answer 6

• GPP
• chemical energy store in plant biomass in a given area in a given time

Question 7

what is the equation linking NPP and GPP?

Answer 7

NPP = GPP - R

Question 8

how can the net production of consumers be calculated?

Answer 8

• N = I - (F + R)
• N = consumers
• I = chemical energy store in ingested food
• F = energy lost in faeces and urine
• R = respiratory losses to the environment