Energy Transfer And Productivity

Question 1

What is the source of energy for ecosystems?

Answer 1

The sun

Question 2

Only a small percentage of the Sun’s energy captured by the heather is eventually incorporated into the body tissues of the fox. What happens to the rest of the energy captured by the heather?

Answer 2

• the heather uses some of the energy for respiration
• the animals convert some of the eaten biomass into energy in respiration – used for movement
• animals transfer energy to the environment as heat
• not all of the plant/animal is eaten
• some is lost to the environment in urine and faeces

Question 3

Green plants only manage to capture 1-3% of the light energy- what happens to the rest of it?

Answer 3

• sun’s energy may be reflected back into space by clouds and dust or absorbed by the atmosphere
• not all wavelengths of light can be absorbed and used for photosynthesis
• light may fall on non-photosynthetic part of the plant (may not fall on chlorophyll molecule)
• a factor such as low carbon dioxide may limit the rate of photosynthesis

Question 4

With the light energy that green plants do absorb, what % of this light energy is converted into biomass?

Answer 4

50-80%

Question 5

What is gross primary productivity?

Answer 5

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

Question 6

What is net primary productivity?

Answer 6

The chemical energy store which is left after what the plant uses in respiration is removed
NPP= GPP-R
Units: kJ/m2/yr or kJ/m3/yr

Question 7

Net production of consumers =

Answer 7

N= I -(F+R)

I= chemical energy of ingested food
F= energy lost in faeces and urine
R= energy lost in respiration