Cycling of Matter – Student Notes Complete (lesson 4)
Biogeochemical Cycles
Matter cannot be made or destroyed.
All water and nutrients must be produced or obtained from chemicals already present in the environment.
This happens through biogeochemical cycles – the movement of matter through biotic and abiotic
environment.
We will investigate four biogeochemical cycles: the water (hydrologic) cycle, the carbon cycle, the
nitrogen cycle, and the phosphorus cycle.
The Water (Hydrologic) Cycle
Liquid water evaporates, forming water vapour that moves through the atmosphere
The vapour condenses, forming liquid water and ice which falls to Earth
The Water Cycle
Fallen water moves around Earth’s surface as lakes, rivers and oceans.
Water is taken up by plants and is released via transpiration or consumed by animals.
The Carbon Cycle
The biogeochemical cycle in which carbon is cycled through the lithosphere, atmosphere, hydrosphere,
and biosphere.
Carbon is an important element, because it is the basic building block of living things.
The Carbon Cycle
Carbon is recycled in the carbon cycle through several processes, but mostly though photosynthesis and
respiration.
Other Processes that Affect the Carbon Cycle
1. CO2 is held dissolved in the oceans.
2. Bogs can store huge amounts organic carbon.
Decaying matter is often trapped, but no oxygen is available to help recycle it.
3. Humans increase the amount of CO2 in the air by burning fossil fuels and by removing vegetation.
Why?
Why does destroying plants increase CO2 in the air?
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Prevents trees from taking up CO2 for photosynthesis
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This leads to more CO2 in the air
The Nitrogen Cycle
The series of processes in which nitrogen compounds (nitrates) are moved through the biotic and abiotic
environment.
Most of the nitrogen is taken from the atmosphere (N2) by soil bacteria in a process called nitrogen fixation
Nitrogen in the soil is available to producers, and pass from producer to consumer through the food web.
Denitrifying bacteria feed on dead plants, animals, and animal waste to release nitrogen gas into the
atmosphere.
The Phosphorus Cycle
Phosphorus is stored in the lithosphere (rocks and sediment)
When rocks are broken down phosphorus is released as (phosphates) PO43- into the soil.
Phosphorus is also used in many fertilizers and detergents which can leak into the waterways
The Phosphorus Cycle
On land, phosphorus is absorbed by plants. Animals then eat the plants and the phosphorus is transferred to
them.
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The Phosphorus Cycle
Phosphorus is a key component of life making up a vital component of DNA and other life sustaining
molecules.
When the animals and plants die, decomposers (bacteria) break down the dead organism and release the
phosphorus back into the soil, continuing the cycle.
The Phosphorus Cycle
Runoff (flow into lakes and ponds) bring the phosphorus into our waterways.