Carbon Cycle
- Overview: The carbon cycle describes the continuous movement of carbon between the Earth’s atmosphere, biosphere, hydrosphere, and geosphere.
- Key Processes:
- Photosynthesis: Plants absorb carbon dioxide from the atmosphere and convert it into organic matter (sugars) during photosynthesis.
- Respiration: Plants, animals, and decomposers release carbon dioxide back into the atmosphere through respiration.
- Decomposition: When organisms die, their organic matter decomposes, releasing carbon dioxide into the atmosphere and soil.
- Ocean-Atmosphere Exchange: Carbon dioxide is exchanged between the atmosphere and the ocean.
- Sedimentation: Carbon can be buried in sediments and eventually form fossil fuels (coal, oil, natural gas) over millions of years.
- Volcanic Activity: Volcanoes release carbon dioxide into the atmosphere.
- Human Activities: Burning fossil fuels, deforestation, and industrial processes release significant amounts of carbon dioxide into the atmosphere.
Nitrogen Cycle
- Overview: The nitrogen cycle describes the movement of nitrogen through the Earth’s atmosphere, soil, and living organisms. Nitrogen is essential for life, but atmospheric nitrogen (N2) is not directly usable by most organisms.
- Key Processes:
- Nitrogen Fixation: The conversion of atmospheric nitrogen (N2) into forms usable by plants (ammonia, nitrates). This can be done by:
- Biological Fixation: Bacteria and certain plants (legumes) can convert atmospheric nitrogen into usable forms.
- Atmospheric Fixation: Lightning can convert atmospheric nitrogen into nitrates.
- Nitrification: The conversion of ammonium (NH4+) to nitrite (NO2-) and then to nitrate (NO3-) by bacteria in the soil.
- Assimilation: Plants absorb nitrate and ammonium from the soil and use them to build proteins and other nitrogen-containing compounds.
- Ammonification: The breakdown of organic nitrogen (from dead organisms and waste) into ammonium by decomposers.
- Denitrification: The conversion of nitrate back into atmospheric nitrogen gas by bacteria in the soil.
- Nitrogen Fixation: The conversion of atmospheric nitrogen (N2) into forms usable by plants (ammonia, nitrates). This can be done by:
Significance of these Cycles
- Life on Earth: Both the carbon and nitrogen cycles are essential for the existence of life on Earth They provide the building blocks for living organisms and regulate the Earth’s climate.
- Climate Change: The carbon cycle plays a crucial role in regulating Earth’s temperature. Human activities, such as the burning of fossil fuels, have disrupted the carbon cycle, leading to increased levels of greenhouse gases in the atmosphere and contributing to climate change.
- Ecosystem Health: Both cycles are vital for maintaining the health and productivity of ecosystems.