The biogeochemical cycle refers to the circulation of an element (e.g. carbon and nitrogen) or chemical compound (e.g. water) as it travels through different parts of an ecosystem. During its journey through nature, it is affected by living and non-living factors, i.e., organisms and temperature, pH, precipitation, wind, sunlight, etc. (1). Some of the most important cycles in nature are the carbon, water, nitrogen and oxygen cycles. All substances found in organisms are part of these cycles. The time it takes for each substance to complete a turn in the cycle is different (1). For example, the carbon cycle is usually divided into a fast and a slow cycle, with the short cycle lasting 1-1000 years and involving the atmosphere, biosphere and hydrosphere, while the slow carbon cycle, which also consists of the lithosphere, can take several million years (2).
Another example of a cycle is the water cycle, which is fuelled by the sun. When the water in lakes and oceans heats up, it evaporates into water vapour, which rises into the atmosphere. As it is colder at higher altitudes, the water condenses into droplets that form clouds and eventually fall as precipitation when they become large and heavy enough. The rain or snow collects in streams and rivers and flows into lakes and oceans. Some water penetrates the soil, where plants absorb it through photosynthesis. Animals and humans then eat the plants, or the water from the plants evaporates back into the atmosphere (3).
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