Bio 130 carbon cycle
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50 Terms
What is the carbon cycle?
The movement of carbon among the atmosphere, biosphere, hydrosphere, and lithosphere in different chemical forms
Why is the carbon cycle essential to life on Earth?
It transfers carbon from the atmosphere to living organisms and back, sustaining nearly all life
What organisms perform photosynthesis?
Photoautotrophs (plants, algae, some bacteria)
What is the basic equation for photosynthesis?
6 CO₂ + 6 H₂O + light → C₆H₁₂O₆ + 6 O₂
Where does photosynthesis occur in plant cells?
Chloroplasts
How do plants take in carbon dioxide?
Through stomata in their leaves
What molecule captures light energy for photosynthesis?
Chlorophyll
What happens to carbon during photosynthesis?
It is fixed from CO₂ into organic molecules (sugars)
What is cellular respiration?
The breakdown of organic compounds to release energy
Where does respiration occur in eukaryotic cells?
Mitochondria
What are the products of respiration?
CO₂, H₂O, and energy
How are photosynthesis and respiration related chemically?
Respiration is the reverse of photosynthesis
What is Gross Primary Productivity (GPP)?
Total carbon fixed by photosynthesis per unit area per unit time
What is Net Primary Productivity (NPP)?
Carbon remaining as biomass after plant respiration
How are GPP and NPP related?
NPP = GPP − plant respiration
What does NPP represent in forests?
New growth (wood, roots, leaves, reproductive structures)
What limits photosynthesis and productivity?
Light, water, nutrients, and climate
How does carbon move from plants to animals?
Through consumption in food webs
What are detritivores?
Organisms that feed on dead organic matter
Why are detritivores important?
They recycle nutrients and release CO₂ through respiration
What is decomposition?
Breakdown of organic matter by detritivores for energy
Why do soils store large amounts of carbon?
Decomposition is limited by temperature, moisture, oxygen, and nutrients
What is a trophic level?
A step in energy transfer from producers to consumers
Why are food webs usually limited to ~3 trophic levels?
energy is lost as heat at each transfer
What is a carbon sink?
A reservoir where carbon is stored long-term
Which carbon sink is the largest on Earth?
Marine sediments and sedimentary rock
Name major carbon stores.
Atmosphere, terrestrial plants, soils, oceans, fossil fuels, sedimentary rocks
How does carbon enter the ocean?
CO₂ diffuses from the atmosphere into seawater
What form does carbon take in ocean water?
Bicarbonate (HCO₃⁻)
How do marine organisms store carbon in shells?
Calcium + bicarbonate → calcium carbonate (CaCO₃)
What is the lithosphere?
Earth’s solid portion containing fossil fuels and sedimentary rock
How were fossil fuels formed?
From ancient organic matter decomposed anaerobically under heat and pressure
What is carbonification?
The process that transforms organic matter into coal, oil, or natural gas
How have humans altered the carbon cycle?
Burning fossil fuels and deforestation
How much CO₂ have humans added since the 1700s?
Over 200 billion metric tons
How much CO₂ do humans emit annually?
~8 billion metric tons
Why does deforestation increase atmospheric CO₂?
It releases stored carbon and removes CO₂-absorbing vegetation
What is the “missing sink”?
CO₂ absorbed by regrowing forests in North America
What does the Keeling Curve show?
A steady rise in atmospheric CO₂ since the late 1950s
Why does atmospheric CO₂ fluctuate seasonally?
Northern Hemisphere forest growth in summer and dormancy in winter
Why is CO₂ considered a greenhouse gas?
It traps outgoing long-wave radiation
What is the enhanced greenhouse effect?
Increased warming due to higher greenhouse gas concentrations
What are predicted impacts of increased CO₂?
Global warming, altered weather, species loss, ocean acidification
How does ocean acidification occur?
Excess CO₂ dissolves into oceans, lowering pH
Why is ocean acidification harmful?
It reduces shell formation in marine organisms
What does carbon neutral mean?
No net CO₂ emissions
What is carbon sequestration?
Long-term storage of carbon to reduce atmospheric CO₂
What is a carbon footprint?
Total CO₂ emissions from an activity or product
What is a carbon credit?
A reduction or offset equal to one ton of CO₂
How can forests help mitigate climate change?
By storing carbon and acting as sinks