Types and Importance of Biochemical Cycle
All the elemental matters tend to go through a cycle in the biosphere which is said to be an interconnected process that is said to be the biogeochemical cycle. There are basically four types of cycles that are present which handle the overall consumption and decaying of nutrients in the environment. There are also materials that are recycled via erosion, weathering, water drainage, and the movement of tectonic plates. These materials are further used by other organisms for their basic functioning.
What is a Biogeochemical Cycle?
The natural pathway through which essential elements in living matter undergo circulation is known as a biogeochemical cycle. The natural elements in the biogeochemical cycles flow from abiotic (non-living) components to biotic (living) components.
Biogeochemical, as a term, refers to three aspects in each cycle. Those aspects are biological, geological, and chemical.
Importance of Biogeochemical Cycle
Biogeochemical cycles help in the regulation of natural elements that are necessary for living beings, by channeling through physical and biological phenomena. It acts as a recycling procedure in nature.
Types of Biogeochemical Cycles
The types of nutrient cycles largely fall under –
Sedimentary cycles- Reservoir in the sedimentary biogeo cycle is Earth’s crust and includes earth-bound elements such as phosphorus, calcium, iron, and sulfur among others.
Gaseous cycles- Reservoirs in the gaseous biogeo cycle are air or ocean and include carbon, oxygen, and nitrogen.
Did You Know?
While the abundance of carbon, hydrogen, and nitrogen are found in the human body, these elements have low occurrences on Earth’s elemental mass. This aspect perhaps will lead you to appreciate biogeochemical cycles' importance. Imagine this, the majority of elements that are so critical to the lives of organisms, are a minuscule percentage of the Earth’s known mass. For instance, nitrogen has only 0.03% share!
Different Types of Cycles
If you are wondering, “what do you mean by biogeochemical cycle?”, a brief discussion on those may help you understand.
The biogeochemical cycle diagrams are indicated by pictorial representation.
Water cycle
Water cycle relates to the movement through various stages such as –
Evaporation- The sun, which is the ultimate source of energy, tends to generate the process of evaporation. This evaporation happens when water molecules present on water bodies tend to rise into the air. This process allows a large amount of water to be present in the atmosphere.
Condensation- The water vapor will then get accumulated in the atmosphere and hence cools down due to the cool temperatures seen at high altitudes. These vapors turn into droplets and ice by coming together to form the clouds.
Precipitation- When there is a temperature above 0 degrees then the vapor condenses to water which is not possible if there is no dust or impurities. Hence the water then attaches itself to the particle's surface and when the droplets are large enough they start precipitating from the clouds. This process is also called rainfall.
Infiltration- Through this process water is then seeped into various layers of soil and it is seen rocks hold less water than soil. While these water may follow streams or rivers, they may also go way below the ground.
Run-off- If the water does not form aquifers and follows gravity then they start flowing down the sides of mountains and hills and hence forming the rivers. This process is called the runoff process.
Water is indispensable for life’s existence, and the ocean plays a vital role in the cycle. Atmospheric water vapor causes precipitation for which evaporation from the water surface is critical. Water cycle also plays a critical role in weather, pressure and temperature in the environment.
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Carbon cycle
Carbon moves from atmosphere to living organisms and back again to the atmosphere. Plants are taken as the starting point of the carbon cycle.
The main stages in the carbon cycle are:
Carbon is taken by plants to use in the process of photosynthesis.
These plants then get consumed by various animals and hence the carbon enters the bodies of these animals.
The animals also eventually die and hence on decomposing they release the carbon back to the atmosphere.
Some of the carbon which is not released engages in the formation of fossil fuels
These fossil fuels are used in various man-made activities and hence more carbon is pumped back into the atmosphere.
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Oxygen cycle
Oxygen cycle is the movement of oxygen through the atmosphere, biosphere and lithosphere. It is released through the process of photolysis.
The main steps of the cycle include the following:
Stage 1: All green plants tend to undergo the process of photosynthesis and release oxygen into atmosphere
Stage 2: All aerobic organisms then inhale oxygen for respiration
Stage 3: This stage includes the removal of carbon dioxide by animals into the atmosphere further taken up by plants during photosynthesis.
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Nitrogen cycle
Nitrogen is essential for life form owing to its presence in nucleic acids and proteins. Plants absorb nitrogen through microbial transformations.
The main steps involved in the cycle –
Nitrogen fixation- In this step the atmospheric nitrogen is primarily available in the inert form which is then converted to ammonia which can be used. During this process the inert form of nitrogen gas is deposited into solid from the atmosphere and surface waters with the help of precipitation. The nitrogen then undergoes a number of processes to combine with the hydrogen to form ammonia. This whole process of nitrogen fixation is done by symbiotic bacteria. The fixation can occur through atmospheric fixation.
Nitrogen assimilation- The primary producers tend to consume the nitrogen compounds with the help of roots and they are present in forms such as ammonia, nitrite ammonium ions or nitrate ions. They are used in the formation of proteins.
Ammonification- When plants or animals die the nitrogen that is present in the organic matter tends to be released back into the soil The decomposers then take action on the nitrogen present in the soil hence producing ammonia by decomposition.
Nitrification- In this process the ammonia will be converted into nitrate which is framed by the oxidation of ammonia done by bacteria of Nitrosomonas species. Nitrates are then converted to nitrates which is an important conversion as the ammonia gas produced is very harmful for plants.
Denitrification- In this step the nitrogen compounds tend to go back to the atmosphere by getting converted to nitrogen from nitrate. This conversion is done by Clostridium and Pseudomonas bacteria.
However, note that this is not sequential order.
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Sulfur cycle
Sulfur, which is present mainly as a component of amino acid, may be found in soil as proteins. It is eventually absorbed by plants as sulfates, through a host of microbial transformations.
The sulfur proteins convert into hydrogen sulfide (H2S) which is further broken down into sulfur in reaction with oxygen. With bacterial action, it becomes sulfate to be absorbed by plants.
The steps seen in Sulfur cycle can be provided as follows:
Decomposition of organic compounds: The proteins tend to release amino acids consisting of sulfur acids which are then reduced to hydrogen sulfide by functioning of bacteria Desulfotomaculum.
Oxidation of hydrogen sulfide to elemental sulfur: This process is done by bacteria belonging to Chlorobiaceae and Chromatiaceae.
Oxidation of elemental sulfur: The sulfur which has turned to its elemental form cannot be readily taken by plants and is hence converted to sulfates by chemolithotrophic bacteria found in soil.
Reduction of Sulfates: The sulfates are then converted to hydrogen sulfide by the bacteria named Desulfovibrio desulfuricans. There are two steps for the same where firstly the sulfates are converted to sulphites by using ATP and the second step consists of reduction of reduction of sulfate to hydrogen sulfide.
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Phosphorus cycle
Phosphorus mainly passes through the hydrosphere, lithosphere and biosphere. It is essential for both animal and plant growth. However, it gradually depletes in soil. In comparison to the carbon cycle, the phosphorus cycle does not pass through the atmosphere. Phosphorus cycle is said to be a very slow process.
The steps involved in Phosphorus cycle can be provided as follows:
Weathering: The phosphate salts are mostly found in rocks and are hence broken down and washed away from the rocks into the ground. Hence it is seen that the process starts from the earth’s crust.
Absorption by Plants: The phosphate salts once dissolved in soil will be absorbed by the plans however the amount taken is very less. Hence some phosphate fertilizers are added by farmers for the plants to take in. However as phosphates do not properly dissolve in water they are not absorbed by the life in aquatic ecosystems.
Absorption by Animals: The animals absorb most of the phosphorus content by consumption of other animals and plants. The rate of phosphorus cycle is faster in most animals compared to as seen in rocks.
Phosphorus being returned to the ecosystem: The plants and animals then tend to die and hence pass on the phosphorus from their body back to the ecosystem which is converted into the inorganic form and recycled to rocks and soil. This step is further again seen by weathering and hence the cycle goes again on.
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Test Yourself
1. Which element is captured by plants for photosynthesis in the course of the carbon cycle?
(a) Heat
(b) Organic carbon
(c) Inorganic carbon
(d) Hydrogen
2. CHNOPS does not include -
(a) Oxygen
(b) Sulfur
(c) Helium
(d) Phosphorus
Learn more about what is a biogeochemical cycle and other related topics through our online classes. You can also download free pdf solutions that will definitely enhance your knowledge.
Key points about Biogeochemical cycles:
Energy keeps on flowing through an ecosystem and is removed as a form of heat but the chemical elements that are present in the biogeochemical cycles tend to be recycled.
The ways in which an element or compound that is present such as water tend to move between various forms of living and nonliving organisms and locations in the biosphere which is said to be the biogeochemical cycle.
Water, carbon, sulfur, and nitrogen cycles are the most important cycles that tend to form the basic part of biogeochemical cycles.
The water cycle is considered to be one of the most important cycles and is an important driver of the biogeochemical cycles.
Conclusion
This is all about the different biogeochemical cycles that take place naturally in our environment. These cycles are often influenced and affected by the different artificial processes we conduct. To understand the importance of these cycles, delve deeper into the concept.
FAQs on Biogeochemical Cycle
1. What is a biogeochemical cycle?
A biogeochemical cycle is the natural pathway through which essential elements, such as carbon, nitrogen, and phosphorus, are continuously circulated from the non-living (abiotic) environment to living organisms (biotic) and back again. These cycles involve a combination of biological, geological, and chemical processes to regulate the availability of nutrients essential for life.
2. What is the main difference between gaseous and sedimentary biogeochemical cycles?
The main difference lies in their primary reservoir.
- Gaseous cycles have their main reservoir in the atmosphere or oceans. These cycles, like the carbon and nitrogen cycles, are generally faster.
- Sedimentary cycles have their main reservoir in the Earth's crust (rocks and soil). These cycles, such as the phosphorus cycle, are typically much slower as they depend on geological processes like weathering.
3. What are the key stages of the water cycle as per the CBSE syllabus?
The water cycle, a crucial driver for other cycles, consists of several key stages:
- Evaporation: The sun's energy heats water bodies, turning liquid water into water vapour that rises into the atmosphere.
- Condensation: The water vapour cools at higher altitudes, turning back into tiny liquid water droplets to form clouds.
- Precipitation: When water droplets in clouds become heavy enough, they fall back to Earth as rain, snow, or hail.
- Infiltration and Runoff: Water that falls on land either seeps into the soil (infiltration) or flows over the surface into rivers and lakes (runoff), eventually returning to the oceans.
4. How does carbon move through the environment in the carbon cycle?
Carbon moves through the environment in a continuous loop. Plants absorb atmospheric carbon dioxide to perform photosynthesis. Animals obtain this carbon by consuming plants or other animals. Carbon is returned to the atmosphere through respiration by both plants and animals. When organisms die, decomposers break them down, releasing carbon into the soil and air. Additionally, human activities like burning fossil fuels release large amounts of stored carbon into the atmosphere.
5. What is the importance of nitrogen fixation in the nitrogen cycle?
Nitrogen fixation is a critical step because most organisms cannot use the abundant nitrogen gas (N₂) directly from the atmosphere. Specialized bacteria convert this inert nitrogen into usable forms like ammonia (NH₃). This process makes nitrogen available to plants, which use it to build essential organic molecules like proteins and DNA. Without nitrogen fixation, the flow of nitrogen into the food web would halt.
6. Why is the phosphorus cycle considered a very slow process compared to others like the carbon cycle?
The phosphorus cycle is significantly slower because it is a sedimentary cycle and does not have a major gaseous or atmospheric phase. Its primary reservoir is in rocks and soil sediments. Phosphorus is released into the ecosystem mainly through the very slow geological process of weathering of rocks. This slow release rate limits its availability and the overall speed of the cycle.
7. What is the specific role of decomposers in nutrient cycling?
Decomposers, such as fungi and bacteria, are essential for completing biogeochemical cycles. Their primary role is to break down the organic matter of dead plants and animals. This decomposition process releases the locked-in essential nutrients (like carbon, nitrogen, and phosphorus) back into the soil, water, and air in an inorganic form. This makes the nutrients available again for producers like plants, thus restarting the cycle.
8. How do human activities disrupt the natural balance of biogeochemical cycles?
Human activities can severely alter the natural speed and balance of these cycles. The burning of fossil fuels adds excess carbon dioxide to the atmosphere faster than it can be removed, contributing to global warming. The extensive use of nitrogen and phosphorus fertilisers in agriculture leads to runoff into water bodies, causing eutrophication, which depletes oxygen and harms aquatic life.
9. How are the food chain and biogeochemical cycles interconnected?
The food chain acts as the primary mechanism for transferring nutrients within the biotic (living) component of an ecosystem. Plants (producers) absorb inorganic nutrients from the environment. When herbivores eat these plants, the nutrients are transferred to them. The nutrients move further up the food chain when carnivores eat the herbivores. This entire process ensures the circulation of matter, directly linking the flow of energy in a food web to the recycling of elements in a biogeochemical cycle.
