| Date | May 2009 | Marks available | 1 | Reference code | 09M.1.SL.TZ1.21 |
| Level | Standard level | Paper | Paper 1 | Time zone | Time zone 1 |
| Command term | Question number | 21 | Adapted from | N/A |
Question
Why do food chains in an ecosystem rarely contain more than five organisms?
A. Nutrients are recycled by the decomposers back to the producers.
B. Nutrients are lost from the ecosystem when organisms die.
C. The conversion of food into growth by an organism is not very efficient.
D. Energy is recycled by the decomposers back to the producers.
Markscheme
C
Examiners report
This question had a very high discrimination index, showing that good candidates were able to distinguish the correct answer.
