Transfer of biomassSpec 4.7.4.3
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.
How biomass is lost
- 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
Efficiency of transfer
Caterpillars eat 250 g of leaves and their body mass increases by 20 g. Calculate the efficiency of biomass transfer.
- Biomass transferred = 20 g.
- Biomass available = 250 g.
- Efficiency = 20 ÷ 250 × 100 = 8%.
Answer: 8%
Effect on numbers of organisms
Because so much biomass is lost at each step, less biomass is available to each higher trophic level. This means fewer organisms can be supported at each higher trophic level, and food chains have only a few trophic levels.
Quick check
What is trophic level 1, and what are those organisms called?
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Plants and algae, called producers.
What is an apex predator?
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A carnivore with no predators.
How do decomposers break down dead material?
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They secrete enzymes into the environment and small soluble food molecules diffuse in.
Approximately what percentage of biomass passes to the next trophic level?
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About 10%.
Give two ways biomass is lost between trophic levels.
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Egested as faeces; lost as carbon dioxide and water in respiration, and as water and urea in urine.