SS1 WEEK 8, BIOLOGY NUTRIENT CYCLING IN NATURE

 

Carbon Cycle

Definition

The carbon cycle is the natural process by which carbon moves between the atmosphere, biosphere, hydrosphere, and lithosphere through biological, chemical, and geological processes.

Processes

1. Photosynthesis: Plants absorb CO₂ from the atmosphere and convert it into organic compounds.
2. Respiration: Organisms release CO₂ back into the atmosphere by breaking down glucose.
3. Decomposition: Microorganisms break down dead organisms, releasing CO₂ into the soil and air.
4. Combustion: Burning fossil fuels and biomass releases CO₂.
5. Ocean Uptake and Release: Oceans absorb CO₂ from the atmosphere, which is later released through marine respiration and decomposition.

Importance

• Maintains atmospheric CO₂ balance.
• Supports plant growth and food chains.
• Regulates global temperature (greenhouse effect).
• Forms fossil fuels over millions of years.
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Nitrogen Cycle

Definition

The nitrogen cycle is the continuous movement of nitrogen in different forms between the atmosphere, soil, water, and living organisms.

Processes

1. Nitrogen Fixation: Bacteria (e.g., Rhizobium) convert atmospheric nitrogen (N₂) into ammonia (NH₃).
2. Nitrification: Ammonia is converted into nitrites (NO₂⁻) and then nitrates (NO₃⁻) by nitrifying bacteria.
3. Assimilation: Plants absorb nitrates and use them to build proteins.
4. Ammonification: Decomposers break down dead matter, converting nitrogen into ammonia.
5. Denitrification: Denitrifying bacteria convert nitrates back into atmospheric nitrogen.

Importance

• Essential for protein and DNA synthesis in living organisms.
• Maintains soil fertility.
• Supports plant and crop growth.
• Regulates atmospheric nitrogen balance.

Oxygen Cycle

Definition

The oxygen cycle is the process by which oxygen is continuously exchanged between the atmosphere, biosphere, and lithosphere through biological and chemical activities.

Processes

1. Photosynthesis: Plants release oxygen into the atmosphere as a byproduct of converting CO₂ and water into glucose.
2. Respiration: Organisms consume oxygen and release CO₂ while producing energy.
3. Decomposition: Breakdown of dead organisms consumes oxygen.
4. Oxidation: Combustion and weathering processes consume oxygen.

Importance

• Supports cellular respiration in living organisms.
• Maintains atmospheric oxygen levels.
• Facilitates oxidation reactions in nature.
• Helps in the formation of the ozone layer (O₃), which protects against UV radiation.
  
  
  

Water Cycle

Definition

The water cycle (hydrological cycle) is the continuous movement of water within the Earth's atmosphere, land, and oceans through various physical processes.

Processes

1. Evaporation: Sun heats water bodies, turning liquid water into vapor.
2. Transpiration: Plants release water vapor into the air through leaves.
3. Condensation: Water vapor cools to form clouds.
4. Precipitation: Water falls as rain, snow, or hail.
5. Infiltration & Percolation: Water soaks into the ground and replenishes groundwater.
6. Runoff: Excess water flows into rivers, lakes, and oceans.

Importance

• Regulates Earth's climate and temperature.
• Distributes fresh water across ecosystems.
• Maintains hydration and survival of organisms.
• Supports agriculture and hydropower generation.
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Tolerance

Definition

Tolerance refers to an organism’s ability to survive and function within a specific range of environmental conditions, such as temperature, humidity, salinity, and pollution.

Types

1. Physiological Tolerance: Adaptation to extreme conditions (e.g., desert plants surviving drought).
2. Ecological Tolerance: Range of conditions a species can survive in.
3. Genetic Tolerance: Genetic variation enabling adaptation to environmental stressors.

Importance

• Determines species distribution and survival.
• Influences biodiversity and ecosystem stability.
• Helps organisms adapt to climate change and habitat changes.
• Essential for agriculture (e.g., drought-resistant crops).