APES UNIT 1 CYCLES

What is the Nitrogen Cycle?

The nitrogen cycle is a biogeochemical process where nitrogen is converted between chemical forms as it moves through the atmosphere, terrestrial, and marine ecosystems. Key steps include nitrogen fixation, nitrification, assimilation, ammonification, and denitrification, which are essential for converting nitrogen into usable forms for living organisms and maintaining ecosystem health.

What is the Carbon Cycle?

The carbon cycle describes how carbon moves between the atmosphere, oceans, land, and living organisms. Key processes include photosynthesis, respiration, decomposition, combustion, and ocean uptake, which regulate the amount of carbon available in different forms and locations, influencing climate and ecosystem productivity.

What is the Water Cycle?

The water cycle, also known as the hydrologic cycle, is the continuous movement of water on, above, and below the surface of the Earth. Key processes in the water cycle include evaporation, transpiration, condensation, precipitation, and infiltration, ensuring the continuous circulation of water and supporting various ecological and environmental functions.

Nitrogen Fixation

Nitrogen fixation is the conversion of atmospheric nitrogen (N2) into ammonia (NH3) or ammonium ($$NH_4^+$), making it accessible to plants. This process can occur biologically through bacteria like Rhizobium, atmospherically through lightning, or industrially via the Haber-Bosch process.

Nitrification

Nitrification is a two-step process where ammonia (NH3) is converted into nitrite (NO2^−) and then into nitrate (NO_3^−) by nitrifying bacteria. This conversion makes nitrogen available for plant uptake and is a critical part of the nitrogen cycle.

Assimilation

Assimilation is the process by which plants absorb ammonium (NH4^+$) and nitrate (NO3^−$$) through their roots. These nitrogen compounds are then incorporated into organic molecules such as amino acids and nucleic acids, supporting plant growth and development.

Ammonification

Ammonification occurs when decomposers, such as bacteria and fungi, break down dead organic matter and waste, releasing ammonium ($$NH_4^+$) back into the soil. This process returns nitrogen to the soil in a form that can be used by plants.

Denitrification

Denitrification is the conversion of nitrate (NO3^−) back into atmospheric nitrogen (N2) or nitrous oxide (N_2O) by denitrifying bacteria. This process occurs in anaerobic conditions and completes the nitrogen cycle.

Photosynthesis

Photosynthesis is the process by which plants and other photosynthetic organisms take up carbon dioxide (CO_2) from the atmosphere and convert it into organic compounds, such as glucose, using sunlight. This process stores carbon in biomass and releases oxygen.

Evaporation

Evaporation is the process by which liquid water changes into water vapor due to solar energy. This phase transition occurs primarily from bodies of water such as oceans, lakes, and rivers, moving water into the atmosphere.

Transpiration

Transpiration is the process through which water is absorbed by plant roots, moves through plants, and is released as vapor from small pores on leaves. It contributes to the moisture in the atmosphere and is a vital component of the water cycle.

Condensation

Condensation is the process by which water vapor in the air cools and changes back into liquid water, forming clouds. This occurs when air rises and cools, allowing water droplets to accumulate.

Precipitation

Precipitation is any form of water, such as rain, snow, sleet, or hail, that falls from clouds and reaches the Earth's surface. This process is crucial for replenishing freshwater sources on land.

Infiltration

Infiltration is the process by which water on the ground surface enters the soil, replenishing groundwater supplies. This process is essential for maintaining soil moisture and supporting plant growth

Surface Runoff

Surface runoff is water flowing over land that reaches bodies of water.

Sublimation

Sublimation is the process where a solid turns directly into a gas, bypassing the liquid phase.

Advection

Advection is the movement of water in the atmosphere due to wind and air currents.

Groundwater Flow

Groundwater flow is the movement of water through underground layers of soil and rock.

Plant Uptake

Plant uptake refers to the absorption of water by plant roots from the soil.