Biogeochemical Cycles
These cycles renew the nutrients required for all life
- Ecosystems vary
- Net primary productivity
- Efficiency of energy flow
- These affect the distribution and abundance of organisms
- Biogeochemical cycles
- Describe the path of essential chemicals through the ecosystem
- Living (biotic)
- Non-Living (abiotic)
- Together these form the closed system of Earth
Carbon Cycle
Carbon
- Essential building block of life
- Exists in many minerals
Carbon Reservoirs
- Most carbon is stored in reservoirs Examples: Fossil fuels, sediment, dissolved in ocean, stored in plant and animals
Atmospheric Carbon
- Most available form for life
- Found as CO2 gas
- Removed from atmosphere by photosynthesis
Organic Carbon
- Terrestrial
- Plants remove CO2 from atmosphere
- Consumers eat plants to obtain carbon
- Release CO2 back into atmosphere through respiration (breathing)
- Decomposers break down complex carbon molecules and release back into cycle
- Aquatic Carbon
- Removed from atmosphere through photosynthesis
- Runs into water from terrestrial system
Nitrogen Cycle
Nitrogen is a vital element in amino acids and is often limiting in plant growth.
Atmospheric Nitrogen
- N2 makes up 75% of Earth's atmosphere
- N2 is not usable by most organisms
- Must be "fixed" to use
- Nitrogen Fixation: process of converting N2 into usable organic compounds
- Performed by specific bacteria
- Combines N2 with hydrogen to create ammonia
Organic Nitrogen
- Nitrogen Assimilation: Plants take in nitrogen from the soil
- Consumers then eat the plants to acquire nitrogen
- Animal waste and decomposition contains nitrogen which is released back into the soil
- Oceans cycle nitrogen in a similar way
Phosphorous Cycle
Phosphorus is necessary for nucleic acids and ATP
- Slowest biogeochemical cycle
- Phosphorus never enters the atmosphere
- Always exists as a solid
- Most common form in nature is the phosphate ion (PO4) 3-
- Terrestrial phosphate is found in minerals, but is inaccessible
- Weathering of rocks eventually releases phosphorus into the soil
- Phosphorus is water soluble
- Over time phosphorus can leach into the oceans, depleting the terrestrial system
