Understanding the Carbon Cycle

• Cycles of matter involve the circulation of matter among Earth, the atmosphere, and living organisms.
• These cycles are crucial for transporting, storing, and making elements like carbon and nitrogen available for biosynthesis.

Carbon Cycle

• This is the movement of carbon between Earth, the atmosphere, and living things.
• Disruption of the carbon cycle by humans contributes to global warming.
• Carbon cycles through photosynthesis, respiration, combustion, and dissolving.
• Photosynthesis uses carbon dioxide, sunlight, and water to produce oxygen and glucose.
• Photosynthesis removes carbon dioxide from the atmosphere, storing it in chemical structures like glucose.
• Carbon moves through the food web as primary consumers eat plants.
• Carbon returns to the atmosphere and soil when organisms die.
• Deforestation reduces carbon dioxide removed via photosynthesis, increasing atmospheric carbon.
• Carbon dioxide is a greenhouse gas; excess amounts in the atmosphere result in global warming and climate change.
• Respiration involves organisms exchanging gases with the environment.
• Cellular respiration uses oxygen and glucose to produce ATP, carbon dioxide, and water.
• Combustion involves burning matter, releasing carbon dioxide into the atmosphere.
• Burning fossil fuels (coal, oil) releases stored carbon into the atmosphere.
• Oceans act as significant carbon reservoirs.
• Carbon dioxide dissolves in water, forming carbonic acid, which can become rock or part of sea animal shells as calcium carbonate.
• Excess carbonic acid in the ocean, due to high carbon dioxide levels, leads to ocean acidification, harming marine ecosystems.

Nitrogen Cycle

• This process moves nitrogen between Earth, the atmosphere, and living organisms.
• Nitrogen is essential for living things, especially in proteins and nucleic acids.
• The atmosphere is 78% nitrogen gas, but this form is unusable for most organisms and must be fixed.
• Nitrogen fixation converts atmospheric nitrogen into usable forms via lightning or special soil bacteria.
• Nitrogen-fixing bacteria convert nitrogen gas to ammonia, which is then transformed into nitrites and nitrates.
• Nitrites and nitrates are forms of nitrogen usable by plants.
• Assimilation allows nitrogen to enter plants and be used to create biomolecules.
• Nitrogen cycles through the food web as plants are consumed.
• Humans disrupt the nitrogen cycle by adding excess nitrogen to ecosystems through fertilizers, causing runoff.
• Excessive nitrogen, a limiting nutrient, can cause eutrophication, disrupting ecosystem balance, especially in aquatic environments.

Comparing Nitrogen and Carbon Cycles

• Element: Carbon and Nitrogen, respectively.
• Carbon cycle steps: Photosynthesis, respiration, combustion, dissolving.
• Nitrogen cycle steps: Fixation, and assimilation.
• Disruption: Increased atmospheric carbon dioxide by deforestation, increased respiration, and fossil fuel combustion which cause climate change; excess nitrogen from fertilizers leads to eutrophication in aquatic ecosystems.