Energy and Ecosystems Flashcards
what do plants synthesise organic products from
- atmospheric or aquatic carbon dioxide
what are the sugars synthesised by plant used for
- most used in respiration
- the rest used to make other groups of biological molecules which form the biomass of a plant
what is Gross Primary Production (GPP)
- the chemical energy store in plant biomass, in a given area or volume in a given time
what is Net Primary Production (NPP)
- the chemical energy store in plant biomass after respiratory losses to the environment have been taken into account
what is the equation that links GPP and NPP
- NPP = GPP - R
- R = respiratory losses
what is a suitable measurement for GPP/NPP
- kJm⁻²yr⁻¹
how to calculate net production of consumers
- N = I - (F+R)
- I = energy in food consumed
- F = energy lost to environment through excretion (faeces)
- R = respiratory losses to the environment as heat
why is the conversion of sunlight into chemical energy the least efficient energy transfer within an ecosystem
- light misses the chlorophyll
- some light is reflected
- some light is the wrong wavelength
why is energy transfer between trophic levels inefficient
- energy lost as heat to environment during respiration
- not all of the organism is consumed or digested
- loss occurs via excretory products
what is biomass
- total mass of carbon or dry mass of tissue per given area per given time
what are typical units for biomass
- kgm⁻² (mass) or kgm⁻³ (volume)
define primary and secondary productivity and their typical units
- the rate of primary and secondary production
- units = kJha⁻²yr⁻¹
describe a method of measuring biomass of plant material
- heat all plant material from known area at 100°C for 15 minutes and then weigh and record the the mass
- reheat at same temperature and reweigh until constant mass is reached which indicates all the water has been removed
- divide dry mass by the area from which the plant material was removed
to determine increases in biomass over time, repeat procedure after specific time periods using same area of plant material
describe a method to determine the amount of chemical energy in dry biomass
calorimetry
- known mass of biomass is completely burnt so that all the energy released is used to heat up a known volume of water
- increase in temp of water is used to calculate the chemical energy of the biomass using Q=mcΔT.
features of a calorimeter that allow it to be a valid measurement of heat energy
- stirrer distributes the heat energy/temperature evenly
- water has a high specific heat capacity
- insulation reduces loss of heat
how does keeping animals confined increase the efficiency of energy conversion
- movement restriction = less energy used in muscle contraction
- warmer environment so less respiration in order to maintain body temperature
- fed food with a high energy content and high digestibility
how to calculate efficiency of energy transfer
(Energy transferred to the next level / Energy available at the previous level) x 100
