5.3 energy and ecosystems Flashcards
producers
autotrophs
use light energy to synthesise their own food
biomass
can be measured in terms of mass of carbon and dry mass of tissue per given area
measuring biomass
sample of organism dried in an oven set to low temperature
-low temp to avoid combustion (loss of biomass/co2)
sample reweighed at regular intervals
all water removed when mass remains constant
mass of carbon taken to be 50% of dry mass
- dry mass more representative as water content of samples varies
calorimetry
can be used to estimate chemical energy stored in dry biomass
sample of dry biomass burnt
energy released is used to heat a known volume of water
change in temperature of water used to calculate the chemical energy
GPP
gross primary production
chemical energy store in plant biomass in a given area or volume, in a given time
i.e. the total energy resulting from photosynthesis
npp
net primary production
chemical energy store in plant biomass after respiratory losses (R) to the environment have been taken into account
NPP = GPP - R
NPP available for plant growth and reproduction
also available to other trophic levels in the ecosystem e.g. herbivores and decomposers
net production of consumers (N)
N = I - (F+R)
I = chemical energy store in ingested food
F = chemical energy lost to the environment in faeces and urine
R = respiratory losses to the environment
rates of productivity units
kJ ha-1 year-1
kj - unit of energy
per unit area as environments vary in size - standardises results so environments can be compared
per year which is more representative as it takes into account the effect of seasonal variation on biomass so environments can be compared
sun > producer
wrong wavelength of light
light strikes non-photosynthetic region e.g. bark
light reflected
lost as heat
producer > primary consumer > etc
respiratory loss - energy used for metabolism e.g. active transport
lost as heat
not all plant/animal eaten e.g. bones
some food not digested > faeces
farming practices to increase energy transfer efficiency
crops
herbicides kill weeds > less competition > more energy to create biomass
fungicides reduce fungal infections > more energy to create biomass
pesticides > reduce loss of biomass from crops
fertilisers e.g. nitrates prevent poor growth due to lack of nutrients
farming practices to increase energy transfer efficiency
livestock
reducing respiratory losses so more energy to create biomass
- restrict movement
- keep warm
slaughter animal whilst still growing when most of their energy is used for growth
selective breeding to produce breeds with higher growth rates
treated with antibiotics to prevent loss of energy due to pathogens
