Energy Transfer and Nutrient Cycles

Question 1

Biomass

Answer 1

The chemical energy stored in a plant

Question 2

Measuring Biomass: Dry Mass

Answer 2

Biomass measured in terms of the mass of carbon that an organism contains or the dry mass of its tissue per unit area

Question 3

Describe procedure for calculating the dry mass

Answer 3

• Dry mass is the mass of the organism with the water removed.
• To measure the dry mass, a sample of the organism is dried often in a oven set to a low temperature.
• The sample is weighed at regular intervals.
• Once the mass becomes constant you know that all the water has been removed

Question 4

Estimating the Amount of Chemical Energy Stored in Biomass

Answer 4

Burn the biomass in a calorimeter.
The amount of heat given off tells you how much energy is in it.
Energy is measured in joules or kilojoules

Question 5

Describe procedure for estimating the amount of chemical energy stored in biomass

Answer 5

• A sample of dry biomass is burnt and the energy released is used to heat a known volume of water.
• The change in temperature is used to calculate the chemical energy of the dry biomass

Question 6

Gross Primary Production (GPP)

Answer 6

The total amount of chemical energy converted from light energy by plants, in a given area

Question 7

Net Primary Production (NPP)

AKA

Units

Answer 7

The energy available to the plant for growth and reproduction- the energy stored in the plant’s biomass.
It is also the energy available to organisms at the next stage in the food chain (ie next trophic level)

Primary Productivity

kj ha (-1) year (-1) or kj m(-2) year (-1)

Question 8

Equation for calculating NPP

Answer 8

NPP= GPP - R 
(R= respiratory loss)

Question 9

Equation for calculating Net Production of Consumers

AKA

Answer 9

N= I - (F + R)

(N= Net Production
I= Chemical energy in ingested food
F= Chemical energy lost in faeces and urine
R= Energy lost through respiration)

Secondary Production (or secondary productivity when it’s expressed as a rate)