**Oxygen Cycle**

The oxygen cycle is a biogeochemical process that describes the movement of oxygen within the Earth's atmosphere, biosphere, and lithosphere. It is essential for the survival of various organisms and plays a crucial role in maintaining ecological balance. The cycle involves the continuous exchange of oxygen between different reservoirs or components of the Earth's system. Let's delve into the details of the oxygen cycle:

1. **Photosynthesis:** The primary source of oxygen in the atmosphere is photosynthesis, a process carried out by green plants, algae, and some bacteria. During photosynthesis, these organisms use sunlight, carbon dioxide, and water to produce oxygen and glucose. Oxygen is released into the atmosphere as a byproduct.

2. **Respiration:** Organisms, including plants and animals, undergo respiration, a process that utilizes oxygen to break down glucose and release energy. During respiration, oxygen is consumed, and carbon dioxide is produced as a waste product. This carbon dioxide can either be utilized by plants during photosynthesis or released back into the atmosphere.

3. **Combustion:** Combustion refers to the process of burning organic matter, such as fossil fuels and biomass. When these substances burn, they combine with oxygen from the atmosphere, releasing carbon dioxide, water, and energy. This combustion process affects oxygen levels by consuming it and increasing carbon dioxide concentrations.

4. **Decomposition:** As organic matter decomposes, oxygen is consumed by microorganisms that break down complex organic compounds into simpler substances. This decomposition process occurs in the soil, water bodies, and other environments. During decomposition, oxygen is utilized, and carbon dioxide and other byproducts are released.

5. **Diffusion and Mixing:** Oxygen constantly moves between the atmosphere, biosphere, and lithosphere through diffusion and mixing processes. Diffusion allows oxygen to move from areas of high concentration to low concentration, facilitating its distribution. Mixing occurs through wind, waves, and other physical processes, which help in exchanging oxygen between different parts of the Earth's system.

**Nitrogen Cycle**

The nitrogen cycle is a biogeochemical process that describes the movement and transformation of nitrogen in various forms within the Earth's ecosystems. Nitrogen is an essential component of amino acids, proteins, and nucleic acids, making it vital for the growth and development of living organisms. The nitrogen cycle consists of several interconnected processes:

1. **Nitrogen Fixation:** Nitrogen gas (N2) from the atmosphere is converted into reactive forms, such as ammonia (NH3) or nitrate (NO3-), through a process called nitrogen fixation. This process is primarily carried out by certain bacteria, which can convert atmospheric nitrogen into a usable form that plants can absorb.

2. **Assimilation:** Plants take up the reactive forms of nitrogen, such as ammonia and nitrate, from the soil through their roots. They incorporate nitrogen into their tissues and use it to synthesize essential molecules like proteins and nucleic acids. Animals obtain nitrogen by consuming plants or other animals.

3. **Ammonification:** When plants or animals die, their organic matter decomposes. During decomposition, nitrogen-containing compounds, such as proteins and nucleic acids, are broken down into simpler forms by bacteria and fungi. This process releases ammonia (NH3) as a byproduct.

4. **Nitrification:** Ammonia produced during ammonification is further transformed by nitrifying bacteria into nitrite (NO2-) and