energy and ecosystems Flashcards
(32 cards)
trophic level
stage of food chain
food chain
describes feeding relationships between producers and consumers
food web
linked food chains to show how animals rely on different sources within a single habitat
producer
photosynthetic organisms that manufacture organic substances using light energy, water, carbon dioxide and mineral ions
consumer
organisms that obtain energy by feeding instead of sunlight
biomass
total mass of living material in a specific area at a given time
how can we measure biomass?
by measuring drymass or mass of carbon due to varying amounts of water
what instrument can be used to measure chemical energy store in dry mass?
- bomb calorimeter: sample of dry material burnt in pure oxygen within sealed container called the bomb
bomb is surrounded by water bath and combustion
causes temperature rise
therefore we can calculate energy released
units for energy released from burnt biomass
kJ /kg
what is productivity?
rate at which energy is transferred to chemical potential energy in biomass
what is primary productivity?
rate at which producers transfer light energy into stored chemical potential energy
why do plants only absorb small % of light energy?
- reflected back
- not all wavelengths can be absorbed and used for photosynthesis
- limiting factors i.e. carbon dioxide
formula for net primary production of plants
NPP=GPP-R
what is net primary production?
total amount of chemical energy left after respiratory losses
what is gross primary production?
total quantity of chemical energy store in plant biomass in a given area or volume in a given time
why is there a low percentage of energy transfer between producers and consumers?
- not all consumed
- faeces
- excretion -urine
- respiration- heat loss
formula for net production of consumers
N=I - (F+R)
what is the unit of productivity?
kJm-2yr-1
formula of percentage efficiency
energy available after transfer
———————————————- x 100
energy available before transfer
what is the purpose of farming practices?
to increase yield by increasing efficiency of energy transfer
how does keeping animals in small enclosures increase the energy-conversion rate?
- restricted movement- less energy for respiration for muscle contraction
- warm environment reduces heat loss
- controlled feeding so that animals receive optimum amount and type of food for maximum growth with no wastage
- exclusion of predactors so there is no loss to other organisms in the food web
why is it important to regulate pest control to increase effiency of energy transfer?
- simplifying food webs reduces/eliminates competitive organisms and plants so more resources of crops such as water light minerals and co2
- prevents damage to crops i.e. feeding from insects which limits photosynthesis and reduces productivity
- disease - may be unfit for human consumption
what problems are faced with pest control?
- conservation of natural respurces for sustainability in the future
- demand for cheap food but need to make a living for famers
why are fertilisers important?
to replenish mineral ions removed from an area due to intensive repeated harvesting which will limit growth
- often minerals are not returned to same place due to agriculture and transported to place for consumption
