Biogeochemical Cycles

Biogeochemical Cycles describe the flow of essential elements from the environment through living organisms and back into the environment.

What Sustains Life on Earth? Solar energy, the cycling of matter, and gravity sustain the earth’s life.

Water Cycle (Hydrologic Cycle)

Hydrological Cycle

Hydrological Cycle 1. Reservoir – oceans, air (as water vapor), groundwater, lakes and glaciers; evaporation, wind and precipitation (rain) move water from oceans to land. 2. Assimilation – plants absorb water from the ground, animals drink water or eat other organisms which are composed mostly of water. 3. Release – plants transpire, animals breathe and expel liquid wastes.

Organism’s Role Intake of water: Organisms take in water and use it to perform life functions (such as photosynthesis or transport of nutrients). Transpiration: Plants release water back into the atmosphere through the process of transpiration (the evaporative loss of water from plants).

Organism’s Role Respiration: All organisms metabolize food for energy and produce water as a by-product of respiration. Elimination: Most organisms need water to assist with the elimination of waste products.

Carbon Cycle Figure 3.27 Natural capital: simplified model of the global carbon cycle. Carbon moves through both marine ecosystems (left side) and terrestrial ecosystems (right side). Carbon reservoirs are shown as boxes; processes that change one form of carbon to another are shown in unboxed print. QUESTION: What are three ways in which your lifestyle directly or indirectly affects the carbon cycle? (From Cecie Starr, Biology: Concepts and Applications, 4th ed., Pacific Grove, Calif.: Brooks/Cole, © 2000)

CO2 & CH4

Carbon Cycle

Carbon Cycle (carbon is required for building organic compounds) 1. Reservoir – atmosphere (as CO2), fossil fuels (oil, coal, natural gas), durable organic materials (for example: cellulose). 2. Assimilation – plants use CO2 in photosynthesis; animals consume plants. 3. Release – plants and animals release CO2 through respiration and decomposition; CO2 is released as wood and fossil fuels are burned.

Organism’s Role Photosynthesis: Photosynthetic organisms take in carbon dioxide from the atmosphere and convert it to simple sugars. Respiration: Organisms break down glucose and carbon is released into the atmosphere as carbon dioxide.

Organism’s Role Decomposition: When organisms die, decomposers break down carbon compounds which both enrich the soil or aquatic sediments and are eventually released into the atmosphere as carbon dioxide. Conversion of biochemical compounds: Organisms store carbon as carbohydrates, proteins, lipids, and nucleic acids in their bodies.

Organism’s Role Combustion: When wood or fossil fuels (which were formed from once living organisms) are burned, carbon dioxide is released into the atmosphere. Weathering of carbonate rocks: When sedimentary rocks weather and decompose, carbon is released into the ocean and eventually into the atmosphere.

Nitrogen Cycle

Nitrogen Cycle

50% fertilizer (Bacteria)

Nitrogen Cycle

Nitrogen Cycle 1. Reservoir – atmosphere (as N2); soil (as NH4+ or ammonium, NH3 or ammonia, N02- or nitrite, N03- or nitrate 2. Assimilation – plants absorb nitrogen as either NH4+ or as N03-, animals obtain nitrogen by eating plants and other animals. 3. Release – Denitrifying bacteria convert N03- back to N2; detrivorous bacteria convert organic compounds back to NH4+ ; animals excrete NH4+, urea, or uric acid.

Organism’s Role Nitrogen-fixation: Nitrogen-fixing bacteria, which are found in the soil, root nodules of plants, or aquatic ecosystems, are capable of converting elemental nitrogen found in the air or dissolved in water into the forms that are available for use by plants Intake of nitrogen: Plants take in the nitrogen through their root systems in the form of ammonia or nitrate and in this way, nitrogen can enter the food chain.

Organism’s Role Decomposition: When an organism dies or from animal waste products, decomposers return nitrogen to the soil. Denitrification: Denitrifying bacteria break down the nitrogen compounds in the soil and release elemental nitrogen, N2, into the atmosphere.