3.4.5

Question 1

What is gross production?

Answer 1

The total quantitative energy that plants in a communities convert to organic matter

Question 2

What is net production?

Answer 2

The rate at which the plants store energy

Question 3

What is the equation to work out net production?

Answer 3

Net production = gross production - respiratory losses

Question 4

What is the low percentage of energy transferred at each stage of the food chain the result of?

Answer 4

• some of the organism is not eaten
• some parts are eaten but cannot be digested and therefore are lost in farces
• some of the energy is lost in excretory materials such as urine
• some energy is lost as heat from respiration

Question 5

What does the relative inefficiency of energy transfer between tropic level explain?

Answer 5

• most food chains only have four or five tropic levels as insufficient energy is available to support a large enough breeding population at tropic levels higher than this.
• the total mass of organisms in a biomass is less at higher tropic levels
• the total amount of energy store is less at each level as one moves up a food chain

Question 6

What equation is used to calculate the efficiently of energy transfer?

Answer 6

Energy transfer = energy available after the transfer DIVIDED energy available before the transfer X 100

Question 7

What is the energy available measured in?

Answer 7

kJ per square metre per year

Question 8

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

Answer 8

• over 90% of the Suns energy is 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 many not fall on the chlorophyll molecule
• A factor such as low carbon dioxide levels may limit the rate of photosynthesis