Environmental Science / Unit 2: Ecosystems and Energy Flow
2.4 The Water and Carbon Cycles
Notes
Biogeochemical cycles move matter between living things (bio), the atmosphere, water, and rock (geo).
- Water cycle: evaporation, transpiration (from plants), condensation, precipitation, runoff, infiltration. Driven by the sun and gravity.
- Carbon cycle: producers take in $CO_2$ by photosynthesis; all organisms release $CO_2$ by respiration; decomposition returns carbon; carbon is stored in fossil fuels, limestone, oceans, and wood.
- Burning fossil fuels and clearing forests move stored carbon into the atmosphere as $CO_2$ faster than natural processes remove it.
- A sink stores a substance (forests, oceans); a source releases it.
- Example: a growing forest acts as a carbon sink; a burning forest is a carbon source.
Practice
Which process releases water vapor from plant leaves into the air?
Transpiration is evaporation of water through plant stomata.
Which process removes carbon dioxide from the atmosphere?
Producers convert $CO_2$ into sugars.
Which is a carbon sink?
A growing forest stores carbon in wood and leaves.
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