Energy Transfer - A2 Flashcards
How do plants use the sugars from photosynthesis?
- as respiratory substrates
- to synthesise other biological molecules
What is biomass?
Total dry mass of tissue or mass of carbon measures over a given time in a specific area.
Suggest the units for biomass.
When an area is being sampled: gm−2.
When a volume (eg. pond) is being sampled: gm-3
How can chemical energy stored in dry biomass be estimated?
- using calorimetry
- energy released = specific heat capacity of water x volume of water (cm3) x temperature increase of water.
Why is bomb calorimetry preferred to normal colorimetry?
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 re-weigh it until the mass recorded is constant.
Define gross primary production.
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 equation between NPP and GPP.
NPP = GGP - R
(R = respiratory losses)
Why is most of the suns energy not converted into organic matter?
- most solar energy absorbed by atmosphere or reflected by clouds
- photosynthetic pigments cannot absorb more wavelengths of light
- not all light falls directly on a chlorophyll molecule
- energy lost as heat during respiration / photosynthesis
How can the net production of consumers be calculated?
N = I - (F+R)
I = chemical energy from ingested food
F = energy lost as faeces and urine
R = respiratory losses
Why does biomass decrease along food chain?
- energy lost in nitrogenous waste (urine) and faeces
- some of the organism is not consumed eg. bones/fur
- energy lost to surroundings as heat
Outline some common farming practices used to increase the efficiency of energy transfer.
- Exclusion of predators: no energy lost to other organisms in the food web (pesticides)
- Artificial heating: reduced energy lost used to maintain constant body temperature
- Restriction of movement
- Feeding is controlled at the optimum
Give the general equation for efficiency.
energy converted to useful form
/
total energy supplied
x 100
Explain why the length of food chains is limited.
- energy is lost at each trophic level
- so there is insufficient energy to support a higher trophic level
