Energy And Ecosystems

Question 1

How do plants use the sugars from photosynthesis?

Answer 1

• as respiratory substrates

- to synthesise other biological molecules

Question 2

What is biomass?

Answer 2

Total dry mass of tissue or mass of carbon measure over a given time in a specific area

Question 3

What are the units for biomass?

Answer 3

• when an area is being sampled : gm-2

- when a volume is being sampled : gm-3

Question 4

How can the chemical energy store in dry mass be estimated?

Answer 4

• using calorimetry

- energy released = specific heat capacity of water x volume of water (cm3) x temperature increase of water

Question 5

Why is bomb calorimetry preferable to simple calorimetry?

Answer 5

Reduces heat loss to surroundings

Question 6

How could a student ensure that all water had been removed from a sample before weighing?

Answer 6

Heat the sample and reweigh it until the mass reading is constant

Question 7

Define gross primary production (GPP)

Answer 7

Total chemical energy in plant biomass within a given volume or area

Question 8

Define net primary productivity (NPP)

Answer 8

Total chemical energy available for plant growth, reproduction and energy transfer to other trophic levels after respiratory losses

Question 9

What is the mathematical relationship between GPP and NPP?

Answer 9

NPP = GPP - R

Question 10

Why is most of the sun’s energy not converted to organic matter?

Answer 10

• most solar energy is absorbed by atmosphere or reflected by clouds
• photosynthetic pigments cannot absorb some wavelengths of light
• not all light falls directly on a chlorophyll molecule
• energy lost as heat during respiration / photosynthesis

Question 11

How can the net production of consumers be calculated?

Answer 11

N = I - (F+R)

I: chemical energy from ingested food
F: energy lost as faeces and urine
R: respiratory losses

Question 12

Why does biomass decrease along a food chain

Answer 12

• energy lost in nitrogenous waste and faeces
• some of the organism is not consumed
• energy lost to surroundings as heat

Question 13

Outline some common farming practices used to increase the efficiency of energy transfer

Answer 13

• exclusion of predators
• artificial heating
• restriction of movement
• feeding is controlled at optimum

Question 14

Give a general equation for % efficiency

Answer 14

Energy converted to a useful form (J) x 100 / total energy supplied (J)

Question 15

Explain why the length of food chains is limited

Answer 15

• energy is lost at each trophic level

- insufficient energy to support a higher trophic level

Question 16

What is a pyramid of biomass?

Answer 16

Diagram that shows the biomass at each trophic level

Question 17

Why is a pyramid of biomass preferable to a pyramid of numbers?

Answer 17

Shape of pyramid of numbers may be skewed since a small number of producers can support many consumers

Question 18

What is the mass of carbon?

Answer 18

• the measure of the mass of carbon an organism has

- about half the dry mass

Question 19

What is secondary/consumer production useful for?

Answer 19

Allows us to study how much energy consumers store in their biomass