Question

3.1.9-12.h: the diagram shows an energy pyramid for a meadow ecosystem. suppose that the plants at the base of the pyramid represent 10,000 units of energy. how much energy is represented by the eagle at the top level of the pyramid? 10,000 units, because energy remains the same in all trophic levels. 900 units, because energy decreases by 1 to 5 percent from one trophic level to the next. 10 units because energy decreases by 10 percent with each trophic level. 0 units, because all energy is concentrated in the lowest trophic levels.

Explanation:

Step1: Identify energy - transfer rule

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

Step2: Calculate energy at each level

Plants (producers) have 10,000 units of energy. Primary consumers get 10% of 10,000, which is $10000\times0.1 = 1000$ units. Secondary consumers get 10% of 1000, which is $1000\times0.1=100$ units. Tertiary consumers get 10% of 100, which is $100\times0.1 = 10$ units. The eagle is at the top - most trophic level (a quaternary consumer in this case), and it gets 10% of the energy of the tertiary consumers. So the energy at the eagle's level is $10\times0.1=1$ unit. But looking at the options, we assume the eagle is considered as a tertiary consumer. So the energy it gets is 10 units.

Answer:

10 units, because energy decreases by 10 percent with each trophic level.