(MAE) Nutrient Cycles Lesson

Nutrient Cycles Lesson

A few of the most important nutrients essential for life on Earth are water, oxygen, carbon, and nitrogen. These nutrients are available in limited amounts. Therefore, they must be reused and recycled continuously between living organisms and their environment. The different nutrient or biochemical cycles are linked together to move matter throughout an ecosystem. The water cycle is connected to the carbon and oxygen cycle by the processes involved in photosynthesis and respiration.

 

Watery Cycle

Water on earth is used over and over. The water cycle is the continuous movement of water between the ocean, air, and land in a cyclic pattern. The three main processes that occur in the water cycle are evaporation, condensation, and precipitation. The sun heats the Earth's surface water, causing that surface water to evaporate into a gaseous state of matter called water vapor. This water vapor then rises into the earth's atmosphere where it cools and condenses into liquid droplets. These droplets combine and grow until they become too heavy and fall to the earth as precipitation. Water is temporarily stored in lakes, glaciers, underground, or living organisms. The water can move from these places by streams and rivers. If the precipitation does not become groundwater, it can run off land and return to the oceans. Animals and plants can also release water vapor into the atmosphere.

 

See description of diagram Links to an external site.

 

Carbon Cycle

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The carbon cycle is the biogeochemical cycle by which carbon is exchanged between living and nonliving parts of an ecosystem. Carbon is found in all living things as well as nonliving things. About 0.03% of the Earth's atmosphere is made up of carbon dioxide. The percentage is increasing due human activities such as burning fossil fuels and deforestation. Carbon dioxide is also found in bodies of water and soil. Decomposers break down carbon molecules in the remains of dead organisms so that it can be released into the soil.  

 

Nitrogen Cycle

The nitrogen cycle represents one of the most important nutrient cycles found in terrestrial ecosystems. Nitrogen is used by living organisms to produce a number of complex organic molecules like amino acids, proteins, and nucleic acids. The supply of nitrogen found in the atmosphere, where it exists as a gas plays an important role for life. Nitrogen is also found in organic matter in soil and the oceans. Despite its abundance in the atmosphere, nitrogen is often the most limiting nutrient for plant growth. This problem occurs because most plants can only take up nitrogen in two solid forms: ammonium ion (NH₄ ⁺ ) and the ion nitrate (NO₃ ^- ). Most plants obtain the nitrogen they need as inorganic nitrate from the soil. Certain kinds of bacteria that live in soil change nitrogen gas into ammonia. This process is called nitrogen fixation. These bacteria reside in the roots of certain plants known as legumes. Animals receive the required nitrogen they need for metabolism, growth, and reproduction by the consuming matter containing molecules of nitrogen in plants. Some of the nitrates that were not used by the plants can be converted back into nitrogen gas. Bacteria in the soil help the nitrogen gas re-enter the atmosphere so that the nitrogen cycle will continue.

See description of diagram Links to an external site.

 

This interactive activity adapted from the University of Alberta illustrates how, through a process called fixation, nitrogen flows from the atmosphere, into the soil, through various organisms, and back to the atmosphere in a continuous cycle.

 

 

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