Ecosystem Energetics II




BIO226 : Ecosystem : Energy : Ecosystem Energetics II

Exercise: Ecosystem Energetics II

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DUE: 23-Apr-99. Work sent after this date will receive a grade of zero.

Mass balance relationships in ecological energetics follow the First Law of Thermodynamics, the conservation of matter and energy. All material has to be accounted for.

This exercise follows the diagram in the textbook on page 138 and the equations on page 140. For all rates, give appropriate units.

1. An animal ingests food at the rate of 500 kcal/m²/yr, excretes 2 kcal/m²/yr, respires 95 kcal/m²/yr, and puts 3 kcal/m²/yr into growth and reproduction. What is this animal's rate of assimilation?

2. How much of the food eaten was not digested, but egested (as fecal matter)?

3. If each gram of dry biomass is equivalent to 4 kcal/m²/yr, what was the rate of production of grams of dry feces?

4. What was the assimilation efficiency?

5. What was the net production efficiency?

6. What was the gross production efficiency?

7. If plants used by the animals as food produced 20,000 kcal/m²/yr, what is the exploitation efficiency of these animals on their food?

8. What is the ecological efficiency for the food chain link from plants to these animals?

9. If jackrabbits respire 140 kcal/m²/yr, net production is 5 kcal/m²/yr, and excretion is 0, what is the jackrabbit's assimilation rate?

10. What is the net production efficiency of the jackrabbits?

11. If the net production of plants used for food is 400 kcal/m²/yr, what is the ecological efficiency of jackrabbits?

12. If the assimilation rate represents only 30% of what the rabbits ingest, what is their total ingestion?

13. What is the difference between the rabbits' rate of ingestion and their rate of assimilation?

14. Using 4 kcal as equivalent to 1 g of dry matter, how many grams is this difference?

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