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Compare how energy and matter flow in an ecosystem and relate this flow to the laws of thermodynamics and matter conservation.
 
  What will be an ideal response?

Answer: Although answers will vary, they should contain the following key concepts. The ultimate source of most energy in the biosphere is the sun. Energy flows from the sun, through phototrophs to chemotrophs, and, finally, is dissipated as heat. This reflects the first law of thermodynamics in that the amount of energy remains constant, although the form of energy changes. All of the energy that enters an ecosystem is conserved but eventually dissipates as heat energy. This also upholds the second law of thermodynamics which states that in every physical or chemical change, the universe always tends toward greater disorder. The conversion of the energy in sunlight to heat is an example of an increase in disorder or entropy. Matter, on the other hand, cycles in an ecosystem between phototrophs, chemotrophs, and inorganic chemicals. This upholds the law of the conservation of mass in all physical and chemical changes. In summary, the flow of energy is unidirectional through an ecosystem, while the flow of matter is cyclical.