Comprehensive Guide to AP Environmental Science: Biogeochemical Cycles

Biogeochemical Cycle

The movement of matter within and between ecosystems involving biological, geological, and chemical processes.

Law of Conservation of Matter

Matter can neither be created nor destroyed; it only changes forms.

Reservoir (Pool)

A place where a nutrient sits for a period of time.

Flux

The rate of movement of nutrients between reservoirs.

Residence Time

The average time an element stays in a particular reservoir.

Carbon Cycle

The cycle that describes the movement of carbon among reservoirs such as the atmosphere, oceans, and sedimentary rock.

Photosynthesis

The process by which producers convert atmospheric CO2 into glucose using solar energy.

Cellular Respiration

The process by which organisms, including plants, break down glucose to release energy, producing CO2.

Sedimentation

The process where dissolved CO2 combines with calcium to form calcium carbonate, contributing to sediment formation.

Ocean Acidification

The decrease in pH of ocean waters due to increased atmospheric CO2 being absorbed by the ocean.

Nitrogen Cycle

The cycle that outlines the movement of nitrogen through the atmosphere, soil, and living organisms.

Fixation

The process of converting atmospheric nitrogen (N2) into ammonia (NH3).

Nitrification

The process where ammonium (NH4+) is converted into nitrites (NO2-) and then nitrates (NO3-) by soil bacteria.

Assimilation

The uptake of nitrates by plants to create organic nitrogen in their tissues.

Ammonification

The conversion of organic nitrogen from dead matter back into ammonium (NH4+) by decomposers.

Denitrification

The process of converting nitrates back into nitrogen gas (N2), returning it to the atmosphere.

Phosphorus Cycle

The slowest biogeochemical cycle, involving the movement of phosphorus through rocks, soil, and living organisms without an atmospheric phase.

Weathering & Erosion

The processes that break down phosphate rocks to release phosphate ions into the environment.

Eutrophication

The process by which excess nutrients, particularly nitrogen and phosphorus, lead to algal blooms and oxygen depletion in water bodies.

Evapotranspiration

The combined process of evaporation from the land and transpiration from plants.

Runoff

Water that moves across the land surface into streams and rivers after precipitation.

Infiltration

The process by which water soaks into the ground, recharging aquifers.

Human Impacts on Carbon Cycle

Activities such as combustion of fossil fuels that release carbon rapidly into the atmosphere.

Human Impacts on Nitrogen Cycle

Excessive use of fertilizers leading to nitrogen runoff and eutrophication.

Human Impacts on Phosphorus Cycle

Use of fertilizers and detergents that introduce phosphates into water bodies, causing eutrophication.

Human Impacts on Water Cycle

Urbanization and deforestation that disrupt natural water movement and recharge patterns.

Limiting Factor in Ecosystems

A nutrient whose scarcity limits plant growth, often phosphorus in many ecosystems.

Deep Ocean

One of the major reservoirs in the carbon and nitrogen cycles, representing a significant storage for carbon dioxide.