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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?
In Earth’s atmosphere, oceans, and land masses.
2. Name a biotic process and an abiotic process that allow nutrients to flow in and out of stores.
Biotic Process – decomposition
Abiotic process – river run-off
3. Photosynthesis is an important process in which carbon and oxygen are cycled through ecosystems.
Describe this process.
Photosynthesis is a chemical reaction that converts solar energy into chemical energy. 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 energy-rich sugars (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.
5. How is decomposition related to the carbon cycle?
Decomposition is related to the carbon cycle because when something is decomposing, it is using carbon to decompose,
and that carbon is put into the earth when the decomposition has completed. It is the same as burning fossil fuels (the
carbon cycle). Decomposition is related to the carbon cycle basically because with both processes, the carbon is entering
the Earth through the soil.
6. What is nitrogen fixation?
This is the process in which nitrogen gas is converted into compounds that contain nitrate or ammonium. Both of these
compounds are usable by plants
7. What is denitrification?
This is the process when nitrogen is returned to the atmosphere.
8. What is eutrophication?
This is 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.
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Land clearing
Agriculture
Urban
expansion
Mining
Industry
Motorized
transport
From the stores (very
rapid, takes tens of
hundreds of years
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 transportation.
2. How do these human activities affect a nutrient cycle?
These activities 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. Over time, as a result, increased amounts of nutrients in the
atmosphere, in the oceans, and on land have significant effects on the environment.
3. On the diagram above, add terms and arrows that could represent the effects of human activity on a nutrient cycle.
Perforated text boxes and arrows are the ones I added.
4. How do changes in nutrient cycles affect biodiversity?
An excess of nutrients of a lack of nutrients can alter the biotic and abiotic conditions necessary for supporting biodiversity.
5. Reflect on your local community. Discuss a human activity that is affecting your local ecosystem.
A human activity that affects my local ecosystem is littering. People dropping trash and even apple cores etc. affects out
ecosystem and how it works, garbage that doesn’t decompose sits on the ground, and is bad for the environment. Another
thing that affects our environment is greenhouse gasses, which affect the ozone layer and the air we breathe and use in
daily life.
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 it makes up organic matter, which is all part of life. Also, a lot of the way the carbon
cycle works contributes carbon dioxide to the atmosphere. This helps with plants that need carbon dioxide to create food
and oxygen.
2. How is carbon stored?
Carbon is stored in vegetation on land, in plants in oceans, in land-based and marine animals, and in decaying organic
matter in soil. Carbon is also found in the atmosphere in the form of carbon dioxide gas, and is stored in its dissolved form,
in the top layers of the ocean. Longer-term stores of carbon are found in intermediate and deep ocean waters are dissolved
in carbon dioxide. In cold waters, this carbon will sink into the ocean floor and stay there for 500 years. On land, long-term
stores of carbon are found in coal deposits and in oil and gas deposits. The largest long-term stores of carbon are found in
marine sediments and sedimentary rock.
3. How is carbon cycled?
A variety of natural processes move carbon through ecosystems. These include photosynthesis, respiration, decomposition,
ocean processes, and events such as volcanic eruptions and large-scale forest fires.
4. Name several human activities that affect the carbon cycle.
Activities such as industry and motorized transportation, land clearing, agriculture, and urban expansion have changed the
natural carbon cycle. Since the Industrial Revolution, the amount of carbon dioxide gas in the atmosphere has increased
over 30 percent.
The Nitrogen Cycle
1. Why is the nitrogen cycle important?
Nitrogen is an important component in DNA and proteins, which are essential for the life processes that take place inside
cells. For animals, proteins are essential for muscle function and many other life functions. For plants, nitrogen is important
for growth.
2. How is nitrogen stored?
The largest store of nitrogen is the atmosphere, where it exists as nitrogen gas. Other major sources of nitrogen include
oceans and organic matter in soil. In terrestrial ecosystems, living organisms, lakes, and marshes also store nitrogen, but in
much smaller amounts.
3. How is nitrogen cycled?
Nitrogen cycle involves processes that make nitrogen available to plants and, eventually, to animals. Three of these
processes are nitrogen fixation, and uptake.
4. Name several human activities that affect the nitrogen cycle.
Human activities have doubled the available nitrogen in the biosphere. Millions of tons of nitrogen are added to the
atmosphere annually in the form of nitrogen oxide and nitrogen dioxide as a result of fossil fuel combustion in power plants
and processes such as sewage treatment. Nitrogen is also released during the burning of fossil fuels in cars, trucks, and
other motorized forms of transportation. Clearing forests and grasslands by burning also releases nitrogen into the air.
These compounds eventually return to the Earth in the form of acid precipitation, or nitric acid.
The Phosphorus Cycle
1. Why is the phosphorus cycle important?
This cycle is essential for a variety of life processes in plants and animals. Phosphorus is an essential element in the
molecule that carries energy to plant cells and animal cells. In plants, phosphorus contributes to root development, stem
strength, and seed production. In humans, a large amount of phosphorus in bones; here, phosphorus works with calcium in
the development of strong bone tissue.
2. How is phosphorus stored?
Phosphorus is not stored in the atmosphere as a gas. Instead, phosphorus is trapped in phosphate that makes up
phosphate rock and the sediments of ocean floors.
3. How is phosphorus cycled?
Phosphorus is cycled by weathering, which releases phosphate into the soil. Chemical and physical weathering are two
types of weathering involved in the phosphorus cycle. In chemical weathering, a chemical reaction causes phosphate rocks
to break down and release phosphate into soil. In physical weathering, processes such as wind, rain, and freezing release
particles of rock and phosphate into soil. On land, plants quickly take up phosphate through their roots and animals obtain
phosphate by eating the plants. The action of decomposers breaking down animal waste and dead organisms, which
returns phosphorus to the soil to become available to producers again. Water plants also take up dissolved phosphate and
pass it through the aquatic food chain. Phosphate also enters aquatic food chains via run-off.
4. Name several human activities that affect the phosphorus cycle.
Phosphate rock is primarily mined to make commercial fertilizes and detergents such as those used in dishwashers. Some
places still mine them for natural fertilizer. Commercial fertilizers, phosphate-containing detergents, animal wastes from
large-scale livestock farming, some industrial waste, and untreated human sewage all enter waterways through run-off and
leaching, thereby contributing additional phosphate to the phosphorus cycle.