13.2 energy transfer and productivity

Question 1

net primary production in producers (NPP) definition

Answer 1

the chemical energy store which is left when respiratory losses have been taken into account

Question 2

gross primary production (GPP) definition

Answer 2

total quantity of the chemical energy store in plant biomass, in a given area or volume, in a given time

Question 3

net primary production equation

Answer 3

NPP= GPP - R

Question 4

what is net primary production used for?

Answer 4

growth, reproduction and for other trophic levels

Question 5

why is there a low percentage of energy transferred at each stage?

Answer 5

• some of the organisms not consumed
• some parts cannot be digested so lost in faeces
• some energy is lost in urine
• some energy losses occur as heat from respiration

Question 6

net production in consumers equation

Answer 6

N= I-(F +R)

Question 7

what do the letters stand for in the net production equation in consumers

Answer 7

N= net production
I= chemical energy store of ingested food
F= energy lost in faeces and urine
R= energy lost in respiration

Question 8

explain the relative inefficiency of transfer between trophic levels

Answer 8

• insufficient energy to support large food chains
• biomass is less at higher trophic levels
• total amount of energy available is less at each level as one moves up a food chain

Question 9

percentage efficiency

Answer 9

energy available after/ energy available before X 100

Question 10

Energy is transferred through an ecosystem. Describe how and explain why the efficiency of energy transfer is different at different stages in the transfer.
[6 marks]

Answer 10

1 Some light energy fails to strike/is reflected/not of appropriate wavelength;
2 Efficiency of photosynthesis in plants is low/approximately 2% efficient;
3 Respiratory loss / excretion / faeces / not eaten;
4 Loss as heat;
5 Efficiency of transfer to consumers greater than transfer to producers/approximately 10%;
6 Efficiency lower in older animals/herbivores/ primary consumers/warm blooded animals/homoiotherms;
7 Carnivores use more of their food than herbivores;