Question

if the producers = 700 j of energy, how many j of energy do the secondary producers have?

Explanation:

Step1: Recall energy - transfer rule

In an ecosystem, only about 10% of the energy is transferred from one trophic level to the next. Producers are at the first trophic level and secondary consumers are at the third trophic level. First, from producers to primary consumers (the second trophic level), the energy transferred is 10% of the producer's energy. Then from primary consumers to secondary consumers, another 10% of the primary - consumers' energy is transferred.

Step2: Calculate energy at primary - consumer level

The energy at the primary - consumer level (first transfer) is 10% of 700 J. So, $E_1 = 0.1\times700=70$ J.

Step3: Calculate energy at secondary - consumer level

The energy at the secondary - consumer level (second transfer) is 10% of the primary - consumer energy. So, $E_2 = 0.1\times70 = 7$ J.

Answer:

7 J