SEV1c Biogeochemical Cycles

The Nitrogen Cycle

The nitrogen cycle is a vital process in nature that converts nitrogen from the atmosphere into forms that can be used by living organisms. It involves several steps: nitrogen fixation, nitrification, assimilation, ammonification, and denitrification.

The nitrogen cycle is a repeating cycle of processes during which nitrogen moves through both living and non-living things: the atmosphere, soil, water, plants, animals and bacteria. In order to move through the different parts of the cycle, nitrogen must change forms.

• Nitrogen fixation: Conversion of atmospheric nitrogen into ammonia by nitrogen-fixing bacteria.

• Nitrification: Conversion of ammonia into nitrite and then into nitrate by nitrifying bacteria.

• Assimilation: Incorporation of nitrate and ammonia into organic compounds by plants and other organisms.

• Ammonification: Decomposition of organic nitrogen compounds into ammonia by bacteria and fungi.

• Denitrification: Conversion of nitrate back into atmospheric nitrogen by denitrifying bacteria.

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Legumes are the best nitrogen-fixing plants. They add nitrogen to the soil naturally. Clover are a common plant that fixes nitrogen.

The picture of the roots above show the nodules where the nitrogen fixing bacteria live.

• Weathering

• Absorption

• Decomposition

• Leaching

• Rock Cycle

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The Phosphorus Cycle

• Phosphorus is an essential nutrient for all living organisms.

• It cycles through the environment in a series of processes.

• Weathering of rocks releases phosphate into the soil.

• Plants absorb phosphate and incorporate it into their tissues.

• Animals obtain phosphorus by consuming plants or other animals.

• Decomposers break down organic matter, releasing phosphate back into the soil

• Phosphorus leaches into the water system.

• Phosphates from dead organisms settle to the bottom of the water and is formed into new rocks.

Human Impact

Human activities such as fertilizer use add nitrogen and phosphorus to the cycle. This can lead to nutrient pollution in water bodies, causing harmful algal blooms.

The Carbon Cycle

The carbon cycle is the process by which carbon is exchanged between the atmosphere, oceans, and living organisms. It plays a crucial role in regulating Earth's climate. Carbon dioxide is absorbed by plants during photosynthesis, transferred to animals through the food chain, and released back into the atmosphere through respiration and decomposition.
Human activities, such as burning fossil fuels, have disrupted this cycle, leading to increased carbon dioxide levels and global warming. Understanding and managing the carbon cycle is essential for mitigating climate change.

Carbon sinks absorb more carbon than they give off. Our forests and oceans are carbon sinks.

Some processes release more carbon dioxide into the atmosphere than they absorb. Burning fossil fuels and raising cattle for food release a lot of carbon.

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The Water Cycle

• Evaporation: The process of water turning into vapor and rising into the atmosphere.

• Condensation: The vapor cools and turns back into liquid, forming clouds.

• Precipitation: Water falls from the clouds as rain, snow, sleet, or hail.

• Runoff: Excess water flows over the land, collecting in rivers, lakes, and oceans.

• Transpiration: Plants release water vapor through their leaves.

Human Activities

Burning fossil fuels and deforestation are major disruptors of biogeochemical cycles. They release large amounts of carbon dioxide, leading to climate change. Additionally, excessive use of fertilizers in agriculture can cause nutrient imbalances in ecosystems. Adopting sustainable practices and reducing our ecological footprint can help mitigate these disruptions.