7.4.3: Transfer of biomass
Not started yet — this one needs some love.
Pyramids of biomass show biomass at different trophic levels.
Producers are mostly plants and algae which transfer about 1% of the incident energy from light for photosynthesis.
Only approximately 10% of the biomass from each trophic level is transferred to the level above it.
Biomass is lost because not all the ingested material is absorbed; some is egested as faeces.
Some absorbed material is lost as waste, such as carbon dioxide and water in respiration and water and urea in urine.
Large amounts of glucose are used in respiration.
Efficiency of biomass transfer can be calculated as biomass transferred to the next level divided by biomass at the current level, then converted to a percentage or fraction.
Food chains usually have fewer organisms at higher trophic levels because biomass is lost at each transfer.
Common exam mistakes
Do not reverse the transfer: only approximately 10% is transferred to the next level, not 90%.
For biomass ratios, use total biomass at each trophic level; do not use the mass of one animal when the question gives a population.
Do not write only "waste"; name undigested material in faeces, excreted urea, carbon dioxide and water from respiration, or uneaten parts.
Faeces are egested material; urea is excreted waste.
For efficiency calculations, divide biomass transferred to the next level by biomass at the current level.