Key Biogeochemical Cycles to Know for AP Environmental Science

Biogeochemical Cycle

The process by which chemical elements are recycled through the Earth's systems, including the atmosphere, hydrosphere, lithosphere, biosphere, and pedosphere.

Carbon Cycle

A cycle involving the movement of carbon through the atmosphere, biosphere, hydrosphere, and geosphere, critical for life.

Photosynthesis

The process where carbon is fixed into organic matter.

Respiration

The process which releases CO2 back into the atmosphere.

Nitrogen Cycle

The cycle in which nitrogen is converted into various chemical forms as it circulates among atmosphere, soil, and living organisms.

Nitrogen Fixation

The conversion of atmospheric nitrogen into ammonia.

Nitrification

The process of converting ammonia to nitrates.

Denitrification

The process that converts nitrates back into nitrogen gas.

Water Cycle (Hydrologic Cycle)

Continuous movement of water on Earth through evaporation, condensation, precipitation, and runoff.

Phosphorus Cycle

The movement of phosphorus through rocks, soil, water, and living organisms, which does not have a gaseous phase.

Sulfur Cycle

The cycle in which sulfur moves through the atmosphere, lithosphere, and biosphere, critical for protein and vitamin structure.

Rock Cycle

Ongoing transformation of rocks through processes like weathering, erosion, sedimentation, and metamorphism.