energy and ecosystems Flashcards
how do plants use the sugars from photosynthesis
primary as respiratory substrates
to synthesise other biological molecules eg 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 eg pond - gm^-3
how can the chemical energy store in dry mass be established
use 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
total chemical energy in plant biomass within a given volume or area
define net primary productivity
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 and NPP
NPP = GPP - 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 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
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 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 (autotrophs) or secondary (heterotrophs) production
biomass in a specific area over a given time period
eg 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 % efficiency
energy converted to a useful form / total energy supplied
