Chapter 25 Lecture Enrichment Ideas
Discuss the laws of thermodynamics and why there is not recycling of energy as there is of chemicals in an ecosystem. Clarify the concept of "heat death" or that all energy eventually dissipates away.
Describe the discovery that energy flow could be traced through an ecosystem by Transeau, who was pressed to present a speech to his state academy of science (see Paul Colinvaux, Why Big Fierce Animals Are Rare, Princeton University Press, 1978).
Discuss why the stored energy in a food web can be represented as a pyramid and why the largest energy level and usually the largest biomass are all located on the producer level, but not necessarily the number of individuals. Humans harvest biomass regularly when mowing a lawn, harvesting hay, commercially fishing, etc.
Ask for a common animal (one for which most can recognize eating habits); trace its food chain back to a plant and forward to the end carnivore; estimate its size and calculate the amounts of food it needs and the amount of carnivore it can support, etc. This will rapidly reveal why there are so few hawks perched alongside country roads or why a city block cannot support very many wild cats.
Point out that the diet of the organism, not the size of the organism, is what makes it part of its trophic level. For example, baleen whales and the largest sharks (whale sharks) both eat plankton.
Adding nutrients to water may not seem intuitively bad. Provide illustrations of eutrophication in local areas.
Watching weather maps provides a view of part of the water cycle. Most water molecules originate as water evaporated from the Pacific Ocean (west coast) or Caribbean (central U.S. and east coast) and has stayed aloft six to nine days.
Back to Lecture Enrichment Ideas