4.7.4 Transfer of biomass

Question 1

how do decomposers break down dead matter?

Answer 1

decomposers release enzymes which catalyse the breakdown of dead material into smaller molecules.

soluble small food molecules then diffuse into the microorganisms

Question 2

what is biomass

Answer 2

the dry mass of all of the living organisms in an area

Question 3

why is dry mass used for biomass?

Answer 3

because the wat mass varies as the volume of water in the organism varies

Question 4

how do you calculate the efficiency of biomass transfer

Answer 4

efficiency = (energy transferred / total energy available) x 100

Question 5

why are biomass transfers not 100% efficient?

Answer 5

energy is lost through

• egestion (removal of faeces)
• excretion (removal of waste products, urine containing urea and water)
• respiration (loss of carbon dioxide and water) in which large amounts of glucose are used.
• the production of inedible bones and shells

Question 6

How much energy as a percentage is transferred by producers from incident light for photosynthesis ?

Answer 6

about 1%

Question 7

Approximately how much biomass, as a percentage, is transferred from a trophic level to the one above it?1

Answer 7

10%

Question 8

List two ways in which biomass can be lost at each stage of a food chain.

Answer 8

Not all ingested food is absorbed- some is lost as faeces.

Not all absorbed food is converted into biomass – some used for keeping constant body temperature or movement.

Question 9

What is the equation which should be used to calculate the efficiency of biomass transfer between trophic levels as a percentage?

Answer 9

efficiency of biomass transfer =

biomass transferred to the next level /
biomass available at the previous level

x 100