Energy transfer between trophic levels is highly inefficient, with only approximately 10% of the energy from one level being passed to the next.
This efficiency limit explains why food chains rarely exceed four or five levels; there is simply not enough energy remaining to support a viable population of higher-level predators.
The energy available to the next level is calculated as:
Decomposers (primarily bacteria and fungi) break down dead organic matter from all trophic levels.
They secrete digestive enzymes to break down complex molecules into soluble nutrients, which they then absorb for energy.
While energy is lost as heat during decomposition, this process is vital for recycling nutrients back into the soil for producers to use again.
| Feature | Food Chain | Food Web |
|---|---|---|
| Structure | Linear, single pathway | Complex, interconnected network |
| Trophic Levels | Each species occupies one level | Species can occupy multiple levels |
| Realism | Simplified model | More accurate representation of ecosystems |
Check the Level: Always identify the producer as Level 1. Students often mistakenly label the first consumer as Level 1.
Energy Calculations: When calculating energy transfer, ensure you move the decimal point correctly for each level (e.g., 10,000 to 1,000 to 100).
Omnivore Placement: In food web questions, remember that an organism can be a secondary consumer in one chain and a tertiary consumer in another; always trace the path from the producer.
Pyramid Shapes: While pyramids of numbers or biomass can sometimes be inverted, pyramids of energy are ALWAYS upright because energy is always lost at each step.
