Discuss the biogeochemical cycles of water, carbon, nitrogen, phosphorus, and sulfur

Energy flows directionally through ecosystems, entering as sunlight (or inorganic molecules for chemoautotrophs) and leaving as heat during the many transfers between trophic levels. However, the matter that makes up living organisms is conserved and recycled. The six most common elements associated with organic molecules—carbon, nitrogen, hydrogen, oxygen, phosphorus, and sulfur—take a variety of chemical forms and may exist for long periods in the atmosphere, on land, in water, or beneath the Earth’s surface. Geologic processes, such as weathering, erosion, water drainage, and the subduction of the continental plates, all play a role in this recycling of materials. Because geology and chemistry have major roles in the study of this process, the recycling of inorganic matter between living organisms and their environment is called a biogeochemical cycle.

The cycling of these elements is interconnected. For example, the movement of water is critical for the leaching of nitrogen and phosphate into rivers, lakes, and oceans. Furthermore, the ocean itself is a major reservoir for carbon. Thus, mineral nutrients are cycled, either rapidly or slowly, through the entire biosphere, from one living organism to another, and between the biotic and abiotic world.

What You’ll Learn to Do

• Discuss the hydrologic cycle and why it is essential for all life on Earth
• Discuss the carbon cycle and why carbon is essential to all living things
• Discuss the nitrogen cycle and nitrogen’s role on Earth
• Discuss the phosphorus cycle and phosphorus’s role on Earth
• Discuss the sulfur cycle and sulfur’s role on Earth

Learning Activities

The learning activities for this section include the following:

• The Hydrologic Cycle
• The Carbon Cycle
• The Nitrogen Cycle
• The Phosphorus Cycle
• The Sulfur Cycle
• Self Check: Biogeochemical Cycles