5.3 Energy & Ecosystems Flashcards
How do plants use sugars from photosynthesis?
Primarily as respiratory substrates
Synthesise other biological molecules
What is biomass?
Total dry mass of tissue or mass of carbon measured over a given time in a specific area or volume
Suggest units for biomass.
Sampled area = gm⁻²
Sampled volume = gm⁻³
How can the chemical energy store in dry biomass be estimated?
Using calorimetry
energy released = specific heat capacity of water x water volume x temperature increase of water
Why is bomb calorimetry preferable to simple calorimetry?
Reduces heat loss to surroundings
How could a student ensure that all water had been removed from a sample before weighing?
Heat the sample and reweigh it until the mass reading is constant
Define Gross Primary Production (GPP).
Total chemical energy in plant biomass within a given volume or area
Define Net Primary Productivity (NPP).
Total chemical energy available for plant growth, plant reproduction and energy transfer to other trophic levels after respiratory losses
Give the mathematical relationship between GPP & NPP.
NPP = GPP - R
R represents respiratory losses
Why is most of the Sun’s energy not converted to organic matter?
Most solar energy absorbed by atmosphere or reflected by clouds
Photosynthetic pigments cannot absorb some light wavelengths
Not all light falls directly on chlorophyll
Energy lost as heat during respiration/photosynthesis
How can the net production of consumers be calculated?
N = I - (F + R)
What does I represent in N = I - (F + R)?
Chemical energy from food
What does F represent in N = I - (F + R)?
Energy lost as faeces/urine
What does R represent in N = I - (F + R)?
Respiratory losses
Why does biomass decrease along a food chain?
Energy lost in urine/faeces
Some of organism not consumed
Energy lost as heat to surroundings
Define primary productivity.
Rate of primary production
Biomass in specific area over a given time period
Define secondary productivity.
Rate of secondary production
Biomass in specific area over a given time period
Outline common farming practices used to increase efficiency of energy transfer.
Exclusion of predators
Aritificial heating
Restriction of movement
Feeding is controlled at optimum
How does exclusion of predators increase the efficiency of energy transfer?
No energy lost to other organisms in food web
How does aritifical heating increase the efficiency of energy transfer?
Reduce energy lost to maintain constant body temperature
Give a general equation for % energy efficiency.
(energy converted to a useful form/total energy supplied) x 100
Explain why the length of food chains is limited.
Energy is lost at each trophic level
Insufficient energy to support higher trophic level
What is a pyramid of biomass?
Diagram that shows the biomass at each trophic level
Why is a pyramid of biomass preferable to a pyramid of numbers?
Shape of pyramid of numbers may be skewed since a small number of producers can support many consumers
