5- Energy and ecosystems Flashcards
Biomass definition
Mass of carbon in an organism
How is biomass measured
Dry mass of tissue per unit area per unit time = kg m2 year1
Calorimetry
- Dry sample in hot oven at 80C to remove all the water - weight until constant mass
- Burn in presence of 100% oxygen in a calorimeter
- Measure energy release/ temp increase of surrounding water- hotter the water the greater the energy stored in biomass
NPP = GPP - R
NPP- Net primary production - chemical energy store left in plant biomass after R
R - Respiratory losses to environment
GPP - Gross primary production - chemical energy stored in plant biomass
Maximising NPP
- Using fertilises to increase growth
- Using insecticides to limit crop damage due to insect pests
- Using herbicides to limit interspecific comp from competing weed species
Net production of consumers (secondary production)
N = I - (F+R)
I- Chemical energy in ingested food
F- Chemical energy lost to environment in faeces and urine
R - Heat energy lost in respiration
Maximising net production
- Feeding concentrated food so it is more digestible and less energy is lost in faeces
-Reducing energy lost by respiration by keeping animals in heated barns and/or restricting movement. - Selective breeding for rapid growth or other desirable characteristics such as meat/fat ratio
Why are energy transfers inefficient - Light energy to producers
- light energy is wrong wavelength so only 1% is transferred to biomass in producers
- Light missed chloroplast - not absorbed by photosynthesis
- Light is reflected from leaf surface
Why are energy transfers between trophic levels in efficient
10% energy is transferred between trophic levels because -
-Some parts of organisms are inedible or indigestible
- Organisms respire which releases heat energy
-Mammals release heat in respiration to maintain body temp
% Efficiency of energy transfer
Net production off trophic level /
net production of previous trophic level
x 100
