Because measuring the amount of energy in each trophic level in an ecosystem is difficult, scientists often collectdata, which tells them the weight of living material at each trophic level. By weighing all the producers, herbivores, and carnivores in an ecosystem, a 90 percent loss of energy from one trophic level to the next has been observed.

a. decomposes use carbon from dead organisms as fuel for cellular respiration, returning carbon dioxide back into the atmosphere.

the "dirty dozen" chemicals banned in an international treaty are formally known as persistent organic pollutants, or pops. the united nations environment program provided this background on what they are and what they can do to humans and wildlife.

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1. the energy lost to disorder metabolism     -entropy

2. related to or possessing motion potential     -kinetic

3. all of the chemical reactions in an organism required for maintenance of the processes of life entropy     -metabolism

4. possible; ability to go into action or perform work kinetic     -potential

5. the study of energy and its transformations thermodynamics     -thermodynamics