Biogeochemical Cycles: Detailed Overview, Environmental Science

What are Biogeochemical Cycles?

The words "bio" and "geo," refer to the biosphere and "geo" and "chemical," refer to the elements that flow through a cycle. These three words altogether are the roots of the phrase "biogeochemical."

Atoms make up the preserved stuff that exists on Earth. Since matter cannot be generated or destroyed, it is recycled in a variety of ways throughout the Earth's system. The remainder of the elements are present in a closed system, and the earth receives energy from the sun that is reflected as heat. Major components include:

• Carbon

• Hydrogen

• Nitrogen

• Oxygen

• Phosphorus

• Sulphur

Types of Biogeochemical Cycles

Essentially, there are two categories of biogeochemical cycles. Both of them are discussed below in the table:

Gaseous Cycle

Major Cycles of Gaseous cycles are discussed below:

Sedimentary Cycles

Some major cycles for the sedimentation cycle are discussed below:

Importance of Biogeochemical Cycles

These cycles provide an example of how energy is utilized. These cycles transport the components needed for life to exist throughout the biosphere. They are essential because they recycle materials, store them as well, and control the essential materials through physical characteristics.

• Ecosystems can continue to exist because of these cycles, which show how living and nonliving entities interact in ecosystems.

• Due to the cycle, there are important processes taking place such as photosynthesis respiration nitrogen fixation which completely rely on the availability of elements which are provided by biogeochemical cycles.

• Cycles like carbon and water cycles are very important for regulating Earth's climatic conditions.

• The biogeochemical cycle is also responsible for breaking down the waste products and decomposing the dead organisms which return the essential nutrients to the ecosystem.

Human Impact on Biogeochemical Cycles

As the human population has grown rapidly in size, anthropogenic activities have greatly altered the natural balance of biogeochemical cycles. These disturbances affect ecosystem health and sustainability.

Nutrient Enrichment

Human activity often removes nutrients from one part of the biosphere and adds them to another. For example, nutrients in farm soil may run off into streams and lakes, depleting nutrients in one area, increasing them in another, and altering chemical cycles in both.

Agriculture and Nitrogen Cycling

After natural vegetation is cleared from an area, the existing reserve of nutrients in the soil is sufficient to grow crops for some time. In agricultural ecosystems, however, a substantial fraction of these nutrients is exported from the area in crop biomass. Nitrogen is the main nutrient lost through agriculture. Thus, agriculture has a great impact on the nitrogen cycle.

Contamination of Aquatic Ecosystems

Nitrogenous minerals in the soil that exceed the limit eventually leach into groundwater or run off into aquatic ecosystems, contaminating water supplies and killing fish. Nutrient runoff can also lead to the eutrophication of lakes,

Acid Precipitation

The burning of wood and of fossil fuels releases oxides of sulfur and nitrogen that react with water in the atmosphere, forming sulfuric and nitric acid, respectively. The acids fall to Earth's surface as acid precipitation that has a pH less than 5.2. Acid precipitation lowers the pH of streams and lakes and affects soil chemistry and nutrient availability.

Greenhouse Gases and Global Warming

Human activities release a variety of gaseous waste products. Increasing atmospheric carbon dioxide concentration and global warming affect ecosystems.

Tips, Tricks, & Mnemonics

It takes effort to remember everything in a single go. We made the entire problem easy. Some of the tricks regarding Biogeochemical Cycle are given below which you can use to memorise the important points.b

Types of Biogeochemical Cycles
"GS: Gaseous, Sedimentary"
G: Gaseous cycles (carbon, nitrogen, oxygen, water cycles)
S: Sedimentary cycles (phosphorus, sulfur, rock cycle)

Water Cycle Stages
"ECPI: Evaporation, Condensation, Precipitation, Infiltration"
E: Evaporation (water turns into vapor)
C: Condensation (vapor turns into clouds)
P: Precipitation (rainfall, snowfall)
I: Infiltration (water seeps into the ground)

Nitrogen Cycle Stages
"FANAD: Fixation, Assimilation, Nitrification, Ammonification, Denitrification"
F: Fixation (conversion of nitrogen gas to ammonia)
A: Assimilation (plants absorb nitrogen)
N: Nitrification (ammonia to nitrate)
A: Ammonification (release of ammonia from dead matter)
D: Denitrification (nitrate to nitrogen gas)

Carbon Cycle Stages
"PPP: Photosynthesis, Plants, Pollution"
P: Photosynthesis (plants absorb carbon)
P: Plants consumed by animals (carbon enters the food chain)
P: Pollution from fossil fuels (carbon returns to the atmosphere)

Phosphorus Cycle
"WARP: Weathering, Absorption, Return, Phosphate"
W: Weathering (rocks release phosphorus)
A: Absorption (plants absorb phosphorus)
R: Return (phosphorus returns to soil through decay)
P: Phosphate (phosphate fertilizers for plants)

Biogeochemical Cycle NEET MCQs

Q1. Which of the following human activities can have a positive impact on nutrient cycling in the ecosystem?

1. Deforestation

2. Agriculture

3. Recycling

4. Industrialization

Correct answer: 3) Recycling

Explanation:

The correct answer is recycling. This can have a positive impact on nutrient cycling in the ecosystem by reducing the amount of waste and allowing the reuse of resources. Deforestation, agriculture, and industrialization can all have negative impacts on nutrient cycling by disrupting natural processes and leading to nutrient loss or depletion. Hence option C is correct.

Option(A) Deforestation has negative impacts on nutrient cycling by disrupting natural processes and leading to nutrient loss or depletion. Hence option A is incorrect.

Option(B) Agriculture has negative impacts on nutrient cycling by disrupting natural processes and leading to nutrient loss or depletion. Hence option B is incorrect.

Option(D) Industrialization can also have negative impacts on nutrient cycling by disrupting natural processes and leading to nutrient loss or depletion. Hence option D is incorrect.

Hence, the correct answer is option 3) Recycling.

Q2. Movement of nutrient elements through the verious components of an ecosystem is called

1. Water Cycle

2. Mineral Cycle

3. Oxygen Cycle

4. Nutrient Cycle

Correct answer: 4) Nutrient Cycle

Explanation:

Nutrient Cycling - The movement of nutrient elements through the various components of an ecosystem is called nutrient cycling. Nutrient cycling refers to the continuous movement of essential nutrient elements, such as carbon, nitrogen, and phosphorus, through the biotic and abiotic components of an ecosystem. Decomposers break down organic matter, releasing nutrients back into the soil or water, where they are reabsorbed by plants. These nutrients are then transferred to herbivores, carnivores, and other organisms through feeding relationships. Efficient nutrient cycling ensures ecosystem stability and supports the growth of producers at the base of the food chain.

Hence, the correct answer is option 4) Nutrient cycle

Q3. Match column 1 with column 2 and select the correct option from the given codes

1. A- 2 , B- 1 ,C- 4 ,D- 3

2. A-3 , B- 1 ,C- 4 ,D- 2

3. A-1 ,B- 3 ,C- 2 ,D- 4

4. A- 2 , B- 3 , C- 4 ,D - 1

Correct answer: 1) A- 2 , B- 1 ,C- 4 ,D- 3

Explanation:

Types of Nutrient cycle -

Nutrient cycles are of two types:
(a) gaseous and
(b) sedimentary.

The reservoir for gaseous type of nutrient cycle (e.g., nitrogen, carbon cycle) exists in the atmosphere and for the sedimentary cycle (e.g., sulphur and phosphorus cycle), the reservoir is located in Earth’s crust.

Hence, the correct answer is option 1) A- 2 , B- 1 ,C- 4 ,D- 3.

Also Read:

• MCQs on Nutrient Cycling

• Productivity in Ecosystem

• Biodiversity and Conservation

FAQs on Biogeochemical Cycle

What are biogeochemical cycles in biology?

Biogeochemical cycles are the pathways through which essential elements and compounds move through the biotic (living) and abiotic (non-living) components of Earth's ecosystems. They are crucial because they enable the recycling and reuse of limited resources, maintain the balance of ecosystems, and support life on Earth by ensuring the availability of essential nutrients and compounds.

What are the two main types of biogeochemical cycles?

1. Gaseous cycles – where the main reservoir is the atmosphere or oceans. Examples: Carbon cycle, Nitrogen cycle, Oxygen cycle.

2. Sedimentary cycles – where the reservoir is in the Earth’s crust. Examples: Phosphorus cycle, Sulphur cycle.

Why are biogeochemical cycles important?

• Maintain the balance of essential nutrients in ecosystems.

• Support life processes like photosynthesis, respiration, and protein formation.

• Prevent accumulation of waste products in nature.

• Help regulate climate and ecosystem stability.
  
  

What are the steps of the nitrogen cycle?

The major pathway for nitrogen to enter an ecosystem is via nitrogen fixation. The conversion of N2 by bacteria to forms that can be used to synthesize nitrogenous organic compounds. Nitrogen fertilizer and precipitation can also provide substantial inputs of NH4+ and NO3- to ecosystems. Ammonification decomposes organic nitrogen to NH4+. In nitrification, NH4+ is converted to N03- by nitrifying bacteria. Under anaerobic conditions, denitrifying bacteria use N03 in their metabolism instead of O2, releasing N2 in a process known as denitrification.