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Science 10 Digital Immersion: Nutrient Cycles
Read our e-textbook pages 68–87.
Nutrient cycles - answer the questions below in sentences.
1. Where are nutrients accumulated or stored for short or long periods?
Nutrients are accumulated in stores.
2. Name a biotic process and an abiotic process that allow nutrients to flow in and out of stores.
A biotic process is decomposition an abiotic process is river run-off.
3. Photosynthesis is an important process in which carbon and oxygen are cycled through ecosystems.
Describe this process.
During photosynthesis carbon in the form of carbon dioxide in the atmosphere enters through the leaves of plants and
reacts with water in the presence of sunlight to produce carbohydrates and oxygen.
4. Cellular respiration is the process in which plants and animals make use of stored energy and release carbon dioxide back
into the atmosphere. Describe this process.
During cellular respiration energy is released within the cells of organisms and made available for growth, repair and
reproduction. Then carbon dioxide gas is released as a waste product.
5. How is decomposition related to the carbon cycle?
Decomposers help to create carbon dioxide by converting organic molecules such as cellulose back into carbon dioxide
which is then released into the atmosphere.
6. What is nitrogen fixation?
Nitrogen fixation is the process in which nitrogen gas is converted into compounds that contain nitrate or ammonium.
7. What is denitrification?
Denitrification is the process in which nitrogen is returned to the atmosphere.
8. What is eutrophication?
The process by which excess nutrients result in increased plant production and decay.
The cycling of nutrients in the biosphere
Use the general model of a nutrient cycle to answer the questions below.
Land Clearing,
Agriculture, Urban
Expansion, Mining,
Industry and
Motorized Transport
From Deep Stores
1. This diagram illustrates the general model of a nutrient cycle. What types of human activities can affect a nutrient cycle?
Land Clearing, Agriculture, Urban Expansion, Mining, Industry and Motorized Transport
2. How do these human activities affect a nutrient cycle?
They can affect the nutrient cycle by increasing the amounts of nutrients in the cycle faster than natural biotic and abiotic
processes can move them back to the stores.
3. On the diagram above, add terms and arrows that could represent the effects of human activity on a nutrient cycle.
Check Diagram
4. How do changes in nutrient cycles affect biodiversity?
If there is an excess of nutrients as a result of change certain plants might not be able to take increased levels of nutrients
and other species which can will outcompete them and grow quickly. If there is a decline in nutrients certain plant species
which need these nutrients will die off and eventually the herbivores that rely on these plants will be without a food source
and will die off from starvation and predation. This will cause a chain reaction because without the herbivores the
carnivores will not have a food source and they too will begin to suffer starvation and die.
5. Reflect on your local community. Discuss a human activity that is affecting your local ecosystem.
In our community the clearing of wooded areas to make new homes is an activity affecting our forests. As more people
want to move into the Lower Mainland wooded areas have to be cleared in order to fit the demand of new homeowners.
With less wooded areas many species native to BC are finding it harder to get the nutrients they need to survive.
Read our e-textbook pages 71–87 about the carbon, nitrogen and phosphorus cycles.
The Carbon Cycle
1. Why is the carbon cycle important?
The carbon cycle is important because carbon is an essential component in the chemical reactions that sustain life
2. How is carbon stored?
Short term stores of carbon are found in vegetation on land, in plants in the ocean, in land and marine animals and in
decaying organic matter in the soil. It can also be found in the atmosphere and in the top layers of the ocean. Long term
stores are found in deep and intermediate ocean waters in the form of carbon dioxide and in coal, oil and gas deposits too.
The largest long term stores of carbon are found in marine sediments and sedimentary rock which can be formed from
calcium carbonate which over time will transform into sedimentary rock full of carbonate rich deposits.
3. How is carbon cycled?
Through a variety of natural processes including photosynthesis, respiration, decomposition, ocean processes and events
including volcanic eruptions and large scale forest fires.
4. Name several human activities that affect the carbon cycle.
The burning of fossil fuels for industry, motorized transportation, clearing land for agriculture and urban expansion
The Nitrogen Cycle
1. Why is the nitrogen cycle important?
Because nitrogen is an important component of DNA and proteins which are essential for the life processes that take place
in cells.
2. How is nitrogen stored?
The largest store of nitrogen is in the atmosphere but other major sources of nitrogen include oceans and organic matter in
soil. Smaller stores of nitrogen include living organisms, lakes and marshes.
3. How is nitrogen cycled?
The nitrogen cycle involves processes that make nitrogen available to plants and eventually animals through processes such
as nitrogen fixation, nitrification and uptake.
4. Name several human activities that affect the nitrogen cycle.
Fossil fuel combustion in power plants, sewage treatment, motorized transportation and clearing forests and grasslands.
The Phosphorus Cycle
1. Why is the phosphorus cycle important?
Because phosphorus is essential for a variety of life processes in plants and animals such as strong bone development in
humans and root development in plants.
2. How is phosphorus stored?
Phosphorous is stored in phosphate which makes up phosphate rock and sediments of the ocean floor.
3. How is phosphorus cycled?
Weathering the process of breaking down rocks into smaller fragments helps to release phosphate into the soil. Chemical
weathering and physical weathering are the two types of weathering involved in the phosphorous cycle. Plants get
phosphate through their roots and the actions of decomposers help to continue the plants access to phosphate. Phosphate
enters aquatic ecosystems through erosion, leaching and run-off. Underwater plants continue to provide phosphorous to
the aquatic organisms. Carnivores obtain phosphorous from eating other consumers with phosphorous in them from either
eating plants or other consumers.
4. Name several human activities that affect the phosphorus cycle.
Mining of phosphate, clearing forests via the slash and burn method and the manufacturing of commercial fertilizers and
detergents.