Energy In Food Chains Flashcards
Less than 3% of sunlight is converted into chemical energy, explain why.
o Sunlight misses leaves entirely
o Only certain wavelengths of light are absorbed by chlorophyll
o Sunlight is reflected from surface of leaves
o Sunlight misses chlorophyll completely so it is not trapped by the chlorophyll
o Energy loss due to inefficiency of photosynthesis (as energy is transferred along the pathways of the light dependent reaction and Calvin cycle)
Only a small percentage of light energy absorbed by chlorophyll is stored as biomass, explain why.
o Photosynthesis is inefficient (2% efficient)
o Energy is lost as electrons are passed on
o Energy is lost by respiration
What is GPP?
Gross primary production (GPP) is the chemical energy store in plant biomass, in a given area or volume.
What is NPP?
Net primary production (NPP) is the chemical energy store in plant biomass after respiratory losses to the environment have been taken into account:
NPP =GPP –R
What is the NPP available for?
Plant growth and reproduction. It is also available to other trophic levels in the ecosystem, such as herbivores and decomposers.
Not all of the energy in the biomass of the plants can be transferred to the consumer. Suggest why.
o Not all parts of the plant can be eaten
o Not all parts eating can be digested and therefore lost in faeces
o Heat energy lost due to respiration
Compare the efficiency of transfer to consumers and to producers.
Efficiency of transfer to consumers is greater than transfer to producers.
The net production of consumers?
N=I–F+R
(where I represents the chemical energy store in ingested food, F represents the chemical energy lost to the environment in faeces and urine and R represents the respiratory losses to the environment.)
The percentage of energy transferred between consumers is generally low. Suggest why.
o Heat lost due to respiration
o Movement/muscle contraction
o Faeces
What happens to the energy in faeces and dead organisms?
o Energy is transferred to decomposers
o Used in growth of decomposers
o Used in respiration of decomposers
o Released as heat
Efficiency is lower in herbivores. Carnivores use more of their food than herbivores. Suggest an explanation for the percentage of energy loss and faeces for the herbivore being larger than that for the carnivore.
o Cellulose present in faeces
o Cellulose/much of food is indigestible
o Indigestible material contains energy
What is primary and secondary productivity?
Primary and secondary productivity is the RATE of primary or secondary production, respectively. It is measured as biomass in a given area in a given time eg kJ ha–1 year–1.
What is dry mass?
Mass of carbon Water removed Way of measuring biomass Estimated using calorimetry Measuring dry mass in given area = gm^-2 Measuring dry mass in given volume = gm^-3
What is the problem with fresh mass?
Varying amounts of water make it unreliable measure of biomass
How would you ensure you had only dry mass/has removed all water?
Heat to high temperature to evaporate water
Keep weighing it
Continue to heat until mass stays constant
