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Lab 6
ENERGY FLOW IN ECOSYSTEMS: by Drs. Edith C. Marsh-Matthews and Michael T. Dixon |
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Waste not, Want not
This process of one organism eating another and then using its energy is very inefficient: we waste much and must eat much. The conversion efficiency varies from approximately 2 – 50%. A rate of 2% means that 98% of the energy is wasted. Half of the energy is wasted when the efficiency is 50% and this is the best that it gets! The remaining energy is lost as heat in various stages of the conversion process (catching the food, chewing, digesting, making new molecules, etc.). As an approximation we will start with an efficiency of 10%, this is a good generalization, particularly for carnivores, plus it makes the math easier!
This inefficiency imposes limitations on the structure of ecosystems. The number of carnivores will be limited by the number of prey which will be limited by the energy that is available in the plants. Producers contain the most energy in an ecosystem and the topmost carnivores have the least amount of energy available to support them.
In this exercise, you will explore the trophic structure of model ecosystems with respect to energy flow and examine the effects of varying conversion efficiencies as well as population parameters on the numbers of individuals that can be supported at the various trophic levels.
In addition to reading the information on these lab web pages you should read pages 148-150 in your textbook.
Don't forget to take the pre-lab quiz on Blackboard. This week you may only take the quiz ONCE.
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