energy and ecosystems Flashcards
how do plants use the sugars from photosynthesis?
- as a respiratory substrate
- to synthesise other biological molecules (cellulose)
what is biomass?
total dry mass of tissue or mass of carbon measured over a given time in a specific area
suggest the units for biomass
- when an area is being sampled: gm-2
- when a volume is being sampled: gm-3
how can the chemical energy store in dry mass be estimated
- calorimetry
- energy released = specific heat capacity of water x volume of water 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/area
define net primary productivity (NPP)
the total chemical energy available for plant growth, plant reproduction and energy transfer to other trophic levels after respiratory losses
give the mathematical relationship between gross primary production (GPP) and net primary production (NPP)
net primary production = gross primary production - R
where R represents respiratory losses
why is most of the sun’s energy not converted to organic matter?
- most solar energy is absorbed by the atmosphere or reflected by clouds
- photosynthetic pigments cannot absorb some 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?
net production = chemical energy from ingested food - (energy lost as faeces and urine + respiratory losses)
why does biomass decrease along a food chain?
- energy lost in nitrogenous waste (urine) and faeces
- some of the organism is not consumed
- energy lost to surroundings as heat
define primary and secondary productivity
- rate of primary or secondary production
- biomass in a specific area over a given time period e.g: kJ ha-1 year-1
outline some common farming practices used to increase the efficiency of energy transfer
- exclusion of predators: no energy lost to other organisms in food web
- artificial heating: reduce energy lost to maintain constant body temperature
- restriction of movement
- feeding is controlled at the optimum
give a general equation for percentage efficiency
(energy converted to a useful form in J / total energy supplied in J) x 100
