Energy Flows and Matter Cycles

Energy follows the laws of thermodynamics which state that Energy is neither lost nor gained but transferred from one form to another.  The second law of thermodynamics states that at every energy conversion, some energy is lost as heat.  Therefore, there will become a point where there will be no useable energy left and energy must be added to the system.  This energy comes from the sun.

The living world is a closed system, it depends on the cycling of matter throughout the ecosystem.  For example, if a tree falls in a forest and doesn’t decompose, all the carbon that is incorporated into the tree’s tissues would remain in that tree rather than going back into the soil.  The amount of carbon dioxide would therefore become less and less as more trees die. This doesn’t happen though.  When a tree dies, it decomposes, and the decomposers break down the tissues back into soil and release carbon dioxide.   Plants can once again use the carbon dioxide for photosynthesis. 

Biogeochemical cycles move matter through the abiotic and biotic world.  Matter such as carbon, water, nitrogen and phosphorus is cycled throughout the ecosystem. When humans interfere with this cycling, it can have drastic effects on the rest of the ecosystem.