Biogeochemical Cycles

Introduction to Biogeochemical Cycles

Biogeochemical cycles describe the movement of chemical elements and compounds between living organisms (biotic components) and non-living (abiotic) reservoirs in the environment. These cycles are essential for sustaining life, as they recycle nutrients necessary for growth, metabolism, and reproduction.

• Biogeochemical cycles include the cycling of elements such as carbon, nitrogen, phosphorus, and water through both living organisms and the physical environment.

• Abiotic reservoirs are locations where chemicals accumulate or are stored outside of living organisms, such as in rocks, soil, water, or the atmosphere.

• These cycles ensure that essential nutrients are available to producers (such as plants) and, through food webs, to consumers (animals and other heterotrophs).

Flow of Energy vs. Cycling of Matter

It is important to distinguish between the flow of energy and the cycling of matter in ecosystems:

• Energy flows in one direction through an ecosystem, typically entering as sunlight and leaving as heat.

• Chemicals/matter are recycled within and between ecosystems through biogeochemical cycles.

• Unlike energy, which is lost as heat, matter is conserved and reused in closed loops powered by the one-way flow of energy.

Main Types of Biogeochemical Processes

Biogeochemical cycles involve several types of processes that move elements through the biosphere:

• Biological processes: Activities performed by living organisms, such as photosynthesis, respiration, eating, and excretion.

• Geological processes: Major movements of matter within and below the Earth's surface, including volcanic eruptions, formation and breakdown of rock, and tectonic activity.

• Chemical and physical processes: Non-living processes such as cloud formation, precipitation, and the flow of running water.

• Human activities: Actions such as mining, burning fossil fuels, clearing land, farming, and burning forests, which can significantly alter natural cycles.

Diagram: Cycling of Matter

The following diagram (described in text) illustrates the cycling of matter between abiotic reservoirs and living organisms:

• Abiotic reservoirs (such as soil, water, and atmosphere) provide nutrients to producers (plants and other autotrophs).

• Producers convert these nutrients into organic forms, which are then passed to consumers (herbivores, carnivores, omnivores) through feeding relationships.

• Decomposers break down dead organisms, returning nutrients to abiotic reservoirs and completing the cycle.

Key Terms

• Biogeochemical cycle: The movement of a particular chemical through the biological and geological (living and non-living) parts of an ecosystem.

• Reservoir: A storage location for a chemical, such as the atmosphere, ocean, or soil.

• Producer: An organism that can make its own food from inorganic substances (e.g., plants, algae).

• Consumer: An organism that obtains energy and nutrients by feeding on other organisms.

• Decomposer: An organism that breaks down dead material, returning nutrients to the environment (e.g., bacteria, fungi).

Example: The Carbon Cycle (Overview)

• Carbon is cycled between the atmosphere, living organisms, oceans, and rocks.

• Photosynthesis by plants removes carbon dioxide from the atmosphere and incorporates it into organic molecules.

• Respiration by plants and animals returns carbon dioxide to the atmosphere.

• Decomposition and geological processes (such as volcanic eruptions) also release carbon back into the environment.

Additional info: The notes above are expanded with academic context to clarify the processes and roles of each component in biogeochemical cycles, as the original slides provided only brief points and images.