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Life's most important compounds

water, carbohydrates, lipids, nucleic acids, proteins

Living organisms are composed mostly of four elements. These four elements (and a few others, such as sulfur and phosphorous) are the basis of life's most important compounds (see above)

oxygen, carbon, hydrogen, and nitrogen

Organisms cannot manufacture these elements, and do not use them up.

Where do essential elements come from? How does their availability affect ecosystems?

Recycling in the Biosphere?

How does matter move through the biosphere? Unlike the one-way flow of energy, matter is recycled within and between ecosystems. Elements pass from one organism to another and among parts of the biosphere through closed loops, called biogeochemical cycles, which are powered by the flow of energy as shown in Figure 3-13 (pg. 79)

Classification of processes involved in biogeochemical processes (4)

1. Biological Processes, which consist of any and all activities performed by living organisms (eating, breathing, "burning" food, and eliminating waste. 2. Geological Processes, which include volcanic eruptions, the formation and breakdown of rock, and major movements of matter within and below the surface of the earth. 3. Chemical and Physical Processes, which include the formation of clouds and precipitation, the flow of running water, and the action of lightening. 4. Human Activity, which includes the mining and burning of fossil fuels, the clearing of land for building and farming, the burning of forests, and the manufacture and use of fertilizers.

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