Question

if the producers in an ecosystem start off with 1000 kj of energy available to them, approximately how much energy will be available to the secondary consumers?
1.000.000 kj
10.000 kj
100 kj
10 kj

Explanation:

Step1: Recall energy - transfer rule

In an ecosystem, about 10% of energy is transferred from one trophic level to the next.

Step2: Determine number of energy - transfer steps

Producers are at the first trophic level, primary consumers at the second, and secondary consumers at the third. So there are 2 energy - transfer steps from producers to secondary consumers.

Step3: Calculate energy available to secondary consumers

Starting with 1000 kJ of energy in producers. After the first transfer (to primary consumers), the energy is $1000\times0.1 = 100$ kJ. After the second transfer (to secondary consumers), the energy is $100\times0.1=10$ kJ.

Answer:

10 kJ