energy transfer between trophic levels Flashcards
reality of energy transfer
- fraction of energy passed on between each successive stage in the chain decreases as it moves along the chain
why is most of the sun energy not used by plants
1) 90% of light energy deriving from sun is reflected back to space by clouds or absorbed by the atmosphere
2) not all wavelengths of light can be absorbed and converted to chemical energy
3) light may not fall on chlorophyll molecule
4) limiting factors such as water or CO2 that affect rate of photosynthesis
gross production
the total quantity of energy that plants in a community convert to organic matter
respiratory losses
energy that plants use for respiration
net production
the rate at which plants store energy
calculated:
gross production - respiratory losses
what results in the low % of energy transferred at each trophic level
1) some of the organisms are eaten
2) some parts are eaten but cannot by digested and are therefore lost through egestion
3) some energy lost in excretory materials e.g. urine
4) some energy is used to maintain constant internal body temperature in warm blooded animals
what 3 things that does relative inefficiency of energy explain
1) most food chains only have 3-4 trophic levels because there is insufficient energy available to support all members of organisms within the habitat
2) biomass is less at higher trophic levels
3) total amount of energy stored is less at each level moving up the food chain
biomass
total mass of an organism in a particular place
can be measured in terms of:
- carbon content
- dry mass of tissue per area at a particular time
calculating the efficiency of energy transfers
energy transfer (percentage efficiency) = (energy available after transfer/energy available before transfer)x100
unit of energy available
kJ m^-2 year^-1
