Question

What is the fundamental difference in how matter and energy move through an ecosystem? Consider the laws of thermodynamics and the law of conservation of matter in your response. How does energy transfer constrain the number of trophic levels in an ecological community?

Answer 1

1. Matter flows through the ecosystem in the form of the non-living nutrients such as carbon, nitrogen, and other elements essential to living organisms. When a living organism dies, these nutrients are released back into the ecosystem. These elements move from the producers, to the consumers, and ultimately to the decomposers when the consumer dies. matter is returned back to the soil by the decomposers. Thus matter is recycled in the ecosystem. This is the law of conservation of matter.

Producers convert energy from the environment into carbon bonds, such as those found in the sugar glucose. When respiration occurs, the carbon-carbon bonds are broken and the carbon is combined with oxygen to form carbon dioxide. This process releases the energy, which is used by the organism to move its muscles, digest food, excrete wastes, think, etc. Unlike matter, energy is not recycled through the system. The energy flow is linear. A part of the energy is lost at each stage. Ultimate fate of energy in ecosystems is for it to be lost as heat.

2. The second law of thermodynamics states that whenever energy is transformed, energy is lost through the release of heat. This occurs when energy is transferred between trophic levels in a food web. Hence, more and more energy is lost as one moves up through trophic levels. If a trophic level has a low amount of energy, the number of organisms supported will be less. Thus energy transfer limits the number of trophic levels a ecosystem can sustain.