Transfer of Energy + Energy Efficiency

Question 1

what are the units for energy in food?

Answer 1

kilojoules

Question 2

unit for energy available at a trophic level in a particular area

Answer 2

kilojoules per square metre per year

Question 3

what are pyramids of energy?

Answer 3

these are drawn to show the total energy available in each trophic level per square per year - there should be a decrease in energy between each trophic level

Question 4

what is the least efficient energy transfer and why?

Answer 4

from light energy to the producer because:

• some light will miss the plant or miss the plant’s chloroplasts
• some light will be reflected by the cuticle
• some light has the wrong wavelength to be absorbed by chlorophyll

Question 5

how much energy is passed from one trophic level to the next?

Answer 5

approximately 10% of energy

Question 6

why is only 10% of energy passed from each trophic level to the next?

Answer 6

• some parts of the organism are not eaten (so the biological molecules are not available for respiration)
• some parts are not digested and absorbed - they are egested as faeces (so the biological molecules are not available for respiration)
• some materials are respired to release energy - the energy is used for:
• muscle contraction e.g. movement and breathing
• maintaining a constant body temperature (in mammals and birds)
• synthesising biological molecules (including excretory products)
• movement of molecules (active transport)
• cell division