GED Science TestLife ScienceEasy
An ecologist is studying the energy flow in a forest ecosystem. She measures the total biomass of producers (trees, plants) and primary consumers (herbivores like deer, rabbits). If the producers in this ecosystem have a biomass of 10,000 kg, what is the *approximate* maximum biomass that could be sustained at the primary consumer level, assuming a typical energy transfer efficiency?
- A10,000 kg
- B1,000 kg
- C100 kg
- D100,000 kg
Show answer & explanationAnswer & explanation
Correct answer: B. 1,000 kg
According to the 10% rule of energy transfer in ecosystems, only about 10% of the energy (and thus biomass) from one trophic level is transferred to the next. Therefore, 10% of 10,000 kg (producers) is 1,000 kg for primary consumers.
Why the other options are wrong
- A. This would imply 100% energy transfer, which is unrealistic due to energy loss at each trophic level.
- C. This would represent a 1% transfer, which is too low for a typical energy transfer efficiency between primary producers and primary consumers (secondary producers).
- D. This would imply a 1000% energy transfer, which is impossible.
Ten Percent Rule (Ecology)
A general rule in ecology stating that, on average, only about 10% of the energy (and biomass) from one trophic level is transferred to the next trophic level; the remaining 90% is lost, primarily as heat.
- Explains why food chains are typically short.
- Energy loss occurs through metabolic processes, waste, and unconsumed biomass.
- Applies to both energy and biomass transfer between trophic levels.
Memory trick: Ten Percent Transferred, Ninety Percent Lost, Life's Cost.