ECOLOGY AND FOOD CHAINS  (18 total points)

You need to bring a piece of graph paper for this Lab.

The Food Chain and the Energy Pyramid

1. The food web, or food chain, is an energy system. The passage of energy upward in the food chain is diagrammed in Figure One. This figure applies to a terrestrial ecosystem in which 10% of the available energy is passed along the food chain to the next level. An example of this energy loss is illustrated in the food chain in Figure Two , a typical food chain in a northern Minnesota forest.

(4) a) Identify the following in Figure Two:
        Primary Producer: __________________________________________
        Consumer 1:          __________________________________________
        Consumer 2:          __________________________________________
        Consumer 3:          __________________________________________

Let's say that the primary production rate for this particular ecosystem is 18,000 kilocalories per square meter per year. On Figure One, the energy change scale on the vertical scale is logarithmic and is given as kilocalories per square meter per year. The trophic level scale on the horizontal scale is arithmetic and is given as trophic stage. The flow of energy is a succession of downward steps, as the trophic level increases.

(2) b) The uppermost point in Figure One (the black dot in the "Producer" section) represents the level of energy stored in the system by the action of primary producers. What is the origin of this stored energy and by what biochemical process is it produced?
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(2) c) When only ten percent of the system energy is passed on to the next higher level, what happens to the remaining 90 percent? Does it leave the system, and if so, how does this happen?
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(4) d) On Figure One, plot four points to show the remaining 90% energy in each stage. (Remember that the primary production is 18,000 kilocalories, so the point that you would plot in the Producer section, for example, should represent 90% of 18,000). Use the vertical scale to accurately plot your points.
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2.  Using a piece of graph paper, label both axes as arithmetic scales. Label the vertical axis as "Rate of Production in kilocalories per square meter per year", using values of 0 to 2000. Label the horizontal axis as "Stage Sequence", using values of 1 to 4.

(4) a) Plot four points to show the 10 % of energy stored at each level. (The point you plot for Trophic Stage 1 , for example, should represent 10% of 18,000). Join the points with a curve.

(2) b) Describe the curve you plotted in. What is the meaning of the shape of the curve?
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