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What are Biogeochemical Cycles?

Angie Bates
Angie Bates

Biogeochemical cycles is the collective name for the cyclical processing of certain substances through living and non-living matter in Earth's biological, geological, and chemical systems. Relatively rare, biogeochemical cycles occur only in atoms which can be found in both organic and inorganic substances. The most common biogeochemical cycles are the nitrogen and the carbon cycle, followed by the oxygen and the hydrologic, or water, cycle.

Nitrogen not only makes up 78.8 percent of Earth's atmosphere, it is also found in proteins in most organic molecules. The nitrogen cycle begins when certain bacteria in the soil near roots of plants combine nitrogen from the air with oxygen or hydrogen atoms to form molecules of NO3, nitrate, or NH3, ammonia, which plants then absorb and process. Herbivorous organisms feed on the plants to gain the nitrogen, and omnivorous animals feed on the herbivores, moving the nitrogen into their bodies. Used nitrogen gets release in animal wastes, which certain bacteria eat, allowing the nitrogen to be released back into the air.

Plants use carbon, in the form of carbon dioxide in their respiration process during photosynthesis and to build tissue.
Plants use carbon, in the form of carbon dioxide in their respiration process during photosynthesis and to build tissue.

Although carbon is only the fourth most abundant element in the world, it is the element that serves as a base for all living things. The carbon cycle consists of carbon being converted into organic matter and then back into inorganic molecules. Plants use carbon, in the form of carbon dioxide in their respiration process during photosynthesis and to build tissue. Animals gain carbon through carbohydrates, releasing the carbon molecules into the air when they breath. When plants and animals die, carbon is released into the air when organisms oxidize the matter.

The oxygen cycle is linked to carbon cycle through the respiration of animals and plants. The second most abundant element in the Earth's atmosphere, oxygen is also essential to most organic material. Oxygen is released into the atmosphere by green plants, which produce it from water and carbon dioxide as a byproduct of photosynthesis. Then, all animals inhale it to allow their bodies to process the sugars they use for energy. Additionally, oxygen in water is cycled through aquatic plants and animals much the same way the oxygen in the air moves through the terrestrial life.

The last of the biogeochemical cycles, the hydrologic cycle, refers to the movement of water. Over a billion tons of water cycles constantly through the Earth. This cycle helps to maintain energy balances. Water enters the air through evaporation at high energy points and is moved by wind to low energy points where it is released via precipitation. On its return to the Earth, water not only replenishes water supplies, which animals drink, it soaks into the soil to be used by plants.

Frequently Asked Questions

What exactly are biogeochemical cycles?

Biogeochemical cycles are natural processes that recycle nutrients in various chemical forms from the environment to organisms and then back to the environment. These cycles are crucial for sustaining life on Earth by regulating the availability of elements like carbon, nitrogen, oxygen, and phosphorus. They ensure that essential nutrients are continually reused and re-purposed throughout ecosystems.

How many types of biogeochemical cycles are there, and what are they?

There are several types of biogeochemical cycles, but the most well-known are the water cycle, carbon cycle, nitrogen cycle, phosphorus cycle, and sulfur cycle. Each cycle plays a unique role in the ecosystem, transferring elements from the physical environment to living organisms and back, thus maintaining the balance of our planet's chemistry and life forms.

Why are biogeochemical cycles important to ecosystems?

Biogeochemical cycles are essential to ecosystems because they regulate the flow of nutrients necessary for organism survival. For instance, the nitrogen cycle converts atmospheric nitrogen into forms usable by plants, which is critical for protein synthesis. Disruptions in these cycles can lead to environmental issues such as eutrophication or climate change, highlighting their importance in ecosystem stability.

How do human activities impact biogeochemical cycles?

Human activities significantly impact biogeochemical cycles. For example, burning fossil fuels alters the carbon cycle by releasing large amounts of carbon dioxide, contributing to climate change. Similarly, the use of synthetic fertilizers affects the nitrogen cycle, often leading to water pollution and eutrophication. These disruptions can have long-term effects on global ecosystems and climate.

Can biogeochemical cycles change over time?

Yes, biogeochemical cycles can change over time due to natural events and human influence. Volcanic eruptions, for instance, can release vast amounts of sulfur, altering the sulfur cycle. Human-induced changes, such as deforestation and industrialization, can also cause shifts in these cycles, often accelerating or decelerating natural processes with potentially harmful ecological consequences.

What role do plants and animals play in biogeochemical cycles?

Plants and animals are integral components of biogeochemical cycles. Plants, through photosynthesis, absorb carbon dioxide and release oxygen, driving the carbon cycle. Animals contribute to the nitrogen cycle by excreting waste, which bacteria then convert into nitrates for plant use. Decomposers break down dead matter, returning nutrients to the soil, thus closing the loop of these cycles.

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    • Plants use carbon, in the form of carbon dioxide in their respiration process during photosynthesis and to build tissue.
      By: designua
      Plants use carbon, in the form of carbon dioxide in their respiration process during photosynthesis and to build tissue.