Nutrient cycles

Photosynthesis removes carbon dioxide from the atmosphere. Plants, algae, and some bacteria use CO₂ along with water and sunlight to produce glucose, a sugar, and oxygen. This converts inorganic carbon into organic compounds.

Respiration releases carbon dioxide back into the atmosphere. Organisms, including plants and animals, break down glucose during respiration, producing energy, water, and CO₂ as a byproduct, returning carbon to the atmosphere.

Feeding transfers carbon compounds from one organism to another. When an animal consumes a plant or another animal, it ingests carbon-containing organic molecules, which are then incorporated into its own biomass or used for energy.

Decomposition breaks down dead organisms and waste, releasing carbon compounds. Decomposers like bacteria and fungi break down organic matter, releasing CO₂ back into the atmosphere and returning nutrients to the soil.

Fossil fuel formation stores carbon underground over long periods. Over millions of years, the remains of dead organisms can be transformed into fossil fuels like coal, oil, and natural gas, effectively removing carbon from the active cycle.

Combustion releases stored carbon from fossil fuels into the atmosphere as carbon dioxide. Burning fossil fuels (

Decomposers break down dead organisms and waste, releasing ammonium ions (NH₄⁺) into the soil. These microorganisms convert organic nitrogen into inorganic forms that plants can eventually use.

Nitrification is the conversion of ammonium ions (NH₄⁺) into nitrate ions (NO₃⁻) by nitrifying bacteria in the soil. This process is essential because plants can more readily absorb nitrate ions from the soil.

Nitrogen fixation is the conversion of atmospheric nitrogen gas (N₂) into ammonia or ammonium ions (NH₄⁺). This is primarily carried out by nitrogen-fixing bacteria in the soil and root nodules of legumes.

Plants absorb nitrate ions (NO₃⁻) from the soil through their roots via active transport. Once absorbed, nitrate ions are used to synthesize amino acids, which are then used to build proteins essential for plant growth and function.

Deamination is the removal of an amino group from an amino acid. This process occurs in the liver and produces ammonia, which is then converted to urea and excreted. The remaining carbon compound can be used for respiration.

Denitrification is the conversion of nitrate ions (NO₃⁻) back into atmospheric nitrogen gas (N₂) by denitrifying bacteria. This process occurs in anaerobic conditions, effectively removing nitrogen from the soil.