HW6

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BSC 385
Homework #6 (Due 4 December 2002)
Fall 2002
Primary Production and Energy Flow in Ecosystems
Contrast each pair of terms in questions 87-89.
87. Food web -vs- Food Chain
88. Net Production vs Net Production efficiency
89. Assimilation-vs-Assimilation Efficiency
Examine the energy budget given below for an aquatic herbivore. Four experimental populations of
animals were reared for 40 days on different concentrations of algae as food.
Food
Energy
Energy of Growth
Energy of
Assimilation Assimilation
Concentration
Consumed
and Reproduction
Respiration
Efficiency
(Cells/ml/day)
(Calories)
(Calories)
(Calories)
(Calories)
(%)
_______________________________________________________________________________________
25,000
6.14
1.07
0.841
50,000
13.58
1.77
0.941
75,000
20.74
2.35
1.020
100,000
29.24
2.93
1.084
_______________________________________________________________________________________
90-91. Complete the table above by calculating assimilation and assimilation efficiency for each food
concentration.
92-93. From data in the table above, construct and correctly label a graph that accurately illustrates the
relationship between assimilation efficiency and the concentration of algal cells fed to this herbivore.
94. In no more than 2 sentences, postulate a logical explanation for the relationship between food concentration
and the assimilation of food illustrated in Q 92-93.
95. Poikilotherms and homeotherms have vastly different net production efficiencies. Which would have the
higher net production efficiency and why?
Recall from earlier in the semester we calculated turnover time of water in the atmospheric reservoir.
Turnover time can be calculated for many ecological variables, for example energy. Assume that a
plant population has a standing stock biomass of 10 kg/m2 and the annual primary production is 1.5
kg/m2/year.
96. Calculate the fraction of the standing stock biomass that is replaced each year by new production. (Show
calculations)
97. At a production rate of 1.5 kg/m2/year, calculate the time (years) necessary to replace the entire standing
stock.
98-100. Locate the questions at the end of the chapter in the text book on primary production and energy flow.
Answer either question 5 or question 8.
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