critical thinking activity living in the nitrogen cycle

• Science Notes Posts
• Contact Science Notes
• Todd Helmenstine Biography
• Anne Helmenstine Biography
• Free Printable Periodic Tables (PDF and PNG)
• Periodic Table Wallpapers
• Interactive Periodic Table
• Periodic Table Posters
• Science Experiments for Kids
• How to Grow Crystals
• Chemistry Projects
• Fire and Flames Projects
• Holiday Science
• Chemistry Problems With Answers
• Physics Problems
• Unit Conversion Example Problems
• Chemistry Worksheets
• Biology Worksheets
• Periodic Table Worksheets
• Physical Science Worksheets
• Science Lab Worksheets
• My Amazon Books

Nitrogen Cycle

The nitrogen cycle is a biogeochemical cycle that converts nitrogen into various forms throughout the ecosystem. Nitrogen is an essential element for life that organisms use in the synthesis of amino acids , proteins , and nucleic acids . Yet, while the atmosphere is rich in nitrogen (about 78%), this nitrogen (N 2 ) is largely inaccessible to cells in its gaseous form. Through the nitrogen cycle, atmospheric nitrogen undergoes various transformations. Living organisms use nitrogen and ultimately return it back to the atmosphere.

Nitrogen Cycle Processes

Several processes play a role in the nitrogen cycle, including both biotic (living) and abiotic (non-living) factors. These processes include nitrogen fixation, assimilation, ammonification, nitrification, and denitrification.

Nitrogen Fixation

Nitrogen fixation is the initial step of the nitrogen cycle, converting inert atmospheric nitrogen (N 2 ) into a bio-available form, ammonia (NH 3 ).

• Biological Fixation : Some types of bacteria convert nitrogen gas into ammonia. In symbiotic associations, bacteria like Rhizobium colonize the root nodules of legumes, converting atmospheric nitrogen into ammonia. Similarly, non-symbiotic bacteria like Azotobacter and cyanobacteria, especially those in aquatic systems, perform nitrogen fixation. The enzyme central to this process is nitrogenase, which facilitates the reduction of N 2 .
• Physical Fixation : Atmospheric processes, such as lightning, also convert atmospheric nitrogen into nitrogen oxides (NO x ). These oxides subsequently react with water, forming nitrates that can be absorbed by plants.

Assimilation

In assimilation, plants take up ammonia and incorporate nitrogen into amino acids, nucleic acids, and other vital organic molecules. Plants predominantly assimilate nitrogen through their roots in the form of nitrates (NO 3 – ) and ammonium ions (NH 4 + ).

Ammonification

As organisms die and waste products accumulate, decomposers—specifically fungi and certain types of bacteria—break down the organic nitrogen within these materials and convert it back into ammonia. This process ensures that nitrogen trapped within organic matter returns to the soil in a form that plants can reuse.

Nitrification

This aerobic process involves the stepwise oxidation of ammonia to nitrite and then to nitrate.

• First, bacteria like Nitrosomonas oxidize ammonia to nitrite (NO 2 – ).
• Following this, Nitrobacter takes over, oxidizing the nitrite to nitrate (NO 3 – ). Nitrification is a critical step of the nitrogen cycle because most plants predominantly utilize nitrates for their nitrogen needs.

Denitrification

Denitrification is essentially the reverse of nitrogen fixation. Here, the nitrates in the soil transform back into atmospheric nitrogen. Anaerobic bacteria, such as Pseudomonas and Clostridium , reduce nitrates and nitrites to gaseous nitrogen, releasing it back into the atmosphere. This process prevents the accumulation of excess nitrates in terrestrial systems.

Dissimilatory Nitrate Reduction

Unlike denitrification, this process doesn’t return nitrogen to the atmosphere. Instead, certain bacteria reduce nitrates to nitrites or ammonia for energy, especially under anaerobic conditions. However, the nitrogen remains in the ecosystem.

Anaerobic Ammonia Oxidation (Anammox)

In an anaerobic environment, specialized bacteria like Brocadia oxidize ammonia using nitrite as the electron acceptor, producing nitrogen gas. Anammox is particularly relevant in aquatic systems, contributing significantly to the removal of fixed nitrogen from the oceans.

Marine Nitrogen Cycle

The marine environment offers unique niches for nitrogen transformation. While many processes mirror their terrestrial counterparts, the deep-sea regions offer unique conditions, such as oxygen minimum zones (OMZs) where processes like anammox and denitrification are prevalent. The ocean floor acts as a nitrogen sink in that organic debris falls and deposits as sediments. Over time, compression converts these particles into sedimentary rock . Geological uplifting eventually returns these rocks to the surface, where weathering releases the nitrogen compounds back into the cycle.

Human Impacts and Consequences

Human activities significantly impact the nitrogen cycle. From agriculture to industry, anthropogenic nitrogen dramatically increases the flux of reactive nitrogen in the environment.

• Agriculture : The synthesis and widespread use of nitrogen-based fertilizers increase crop yields, but at the cost of nitrogen runoff that causes eutrophication and acidification in aquatic systems. Inorganic nitrogen in water systems also poses toxicity issues for humans and other animals.
• Burning of Fossil Fuels : Burning fossil fuels releases NOx into the atmosphere, which returns to the earth’s surface as acid rain or contribute to smog and greenhouse gas accumulation.
• Deforestation and Land Use Changes : Deforestation alters the natural nitrogen balance, leading to soil degradation and other ecological shifts.

The repercussions of these impacts are multi-fold, affecting air and water quality, disrupting natural ecosystems, and posing direct and indirect health risks to humans.

• Camargoa, Julio A.; Alonso, Álvaro (2006). “Ecological and toxicological effects of inorganic nitrogen pollution in aquatic ecosystems: A global assessment”. Environment International . 32 (6): 831–849. doi: 10.1016/j.envint.2006.05.002
• Erisman, J. W.; Galloway, J. N.; et al. (2013). “Consequences of human modification of the global nitrogen cycle”. Philosophical Transactions of the Royal Society B: Biological Sciences . 368 (1621): 20130116. doi: 10.1098/rstb.2013.0116
• Fowler, David; Coyle, Mhairi; et al. (2013). “The global nitrogen cycle in the twenty-first century”. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences . 368 (1621): 20130164. doi: 10.1098/rstb.2013.0164
• Galloway, J. N.; Townsend, A. R.; et al. (2008). “Transformation of the Nitrogen Cycle: Recent Trends, Questions, and Potential Solutions”. Science . 320 (5878): 889–892. doi: 10.1126/science.1136674
• Voss, M.; Bange, H. W.; et al. (2013). “The marine nitrogen cycle: recent discoveries, uncertainties and the potential relevance of climate change”. Philosophical Transactions of the Royal Society B: Biological Sciences . 368 (1621): 20130121. doi: 10.1098/rstb.2013.0121

Related Posts

Interactive Models

• The Nitrogen Cycle Game

Students will explore the Nitrogen Cycle by modeling the movement of a nitrogen atom as it passes through the cycle. Students will stop in the different reservoirs along the way, answering questions about the processes that brought them to the different reservoirs.  

This lesson was based on an activity from UCAR Center for Science Education . 

Materials Required

• Google Slides: Nitrogen Cycle Game 
• Google Forms: The Nitrogen Cycle Game student response form
• Access to internet
• Computer, tablet, or other device
• Earth System Graphic Organizer (optional)
• Discuss nitrogen with your class. Where is nitrogen found on Earth? Why is it important?  What are some processes that help move nitrogen through the cycle? 
•   Show The Nitrogen Cycle video.

Video: The Nitrogen Cycle

The Nitrogen Cycle | https://www.youtube.com/watch?v=PfqvACMyg68 | Source: Sciencefilmusc2016

• Explain the Google Slide for the Nitrogen Cycle Game & read the overview.
• What are some of the processes that help move nitrogen through from one reservoir to another?
• What are some ways that humans can make an impact on the nitrogen cycle?
• Next, model for students how to click on the sphere icon to move between reservoirs throughout the game.
• Roll the number cube (or virtual die) to determine which center you will go to first. 
• Locate this icon on the Nitrogen Reservoirs Slide and click on the hyperlink.  This will take users to the first of two sequential slides that provide information that they will document in their response sheet (Form or other).
• It is important to record the process that brings you to the different reservoirs.
• Click the “where to go” button to transport you to the next slide. 
• Roll the dice again and click the button that corresponds with the number you rolled.
• Review the Google Form (or worksheet) where students document their nitrogen journey.
• Proceed to play.  After at least five-10 rounds, pull the class together to review their journey.
• Have students share their journeys.
• Fixation : converts nitrogen in the air to ammonium, biologically available
• Nitrification : bacteria change ammonium to nitrates to be absorbed by plants
• Assimilation : plants absorb nitrates by the roots
• Ammonification : decomposers change nitrogen into ammonium to re-enter the cycle
• Denitrification : nitrogen in the soil gets back into the air
• How similar or different are the different journeys that the students made?
• How long could the nitrogen cycle journey continue? 
• Students will fill out the Google Form.
• Consider having students complete the Earth System Graphic Organizer to document the sphere interactions.

Teacher Note

Most of the nitrogen on Earth is in the atmosphere. Approximately 80% of the molecules in Earth’s atmosphere are made of two nitrogen atoms bonded together (N 2 ). All plants and animals need nitrogen to make amino acids, proteins and DNA, but the nitrogen in the atmosphere is not in a form that they can use. Atmospheric nitrogen must undergo a process called nitrogen fixation to be usable by living things. This can happen when molecules are torn apart by lightning or fire, by nitrogen fixing bacteria, or by bacteria from legumes. Other plants get the nitrogen they need from the soils or water in which they live mostly in the form of inorganic nitrate (NO 3 - ). Nitrogen is a limiting factor for plant growth. Animals get the nitrogen they need by consuming plants or other animals that contain organic molecules composed partially of nitrogen. When organisms die, their bodies decompose bringing the nitrogen into soil on land or into the oceans. As dead plants and animals decompose, nitrogen is converted into inorganic forms such as ammonium salts (NH 4 + ) by a process called mineralization. The ammonium salts are absorbed onto clay in the soil and then chemically altered by bacteria into nitrite (NO 2 - ) and then nitrate (NO 3 - ). Nitrate is the form commonly used by plants. It is easily dissolved in water and leached from the soil system. Dissolved nitrate can be returned to the atmosphere by certain bacteria in a process called denitrification.

Certain actions of humans are causing changes to the nitrogen cycle and the amount of nitrogen that is stored in reservoirs. The use of nitrogen-rich fertilizers can cause nutrient leading in nearby waterways as nitrates from the fertilizer wash into streams and ponds. The increased nitrate levels cause plants to grow rapidly until they use up the nitrate supply and die. When the plant supply increases, so do the number of herbivores. However, when the plant supply dies off, there is increased resource competition in the herbivore population. In this way, changes in nutrient supply will affect the entire food chain. Additionally, humans are altering the nitrogen cycle by burning fossil fuels and forests, releasing various solid forms of nitrogen. Farming also affects the nitrogen cycle. The waste associated with livestock farming releases a large amount of nitrogen into soil and water. In the same way, sewage waste adds nitrogen to soils and water.

• The Nitrogen Cycle Game | Center for Science Education . (n.d.). UCAR Center for Science Education. Retrieved April 14, 2023, from https://scied.ucar.edu/activity/nitrogen-cycle-game
• Krebs, E., Delac, J., & Smat, R. (2016, May 10). The Nitrogen Cycle . YouTube. Retrieved April 14, 2023, from https://www.youtube.com/watch?v=PfqvACMyg68

Teachers who are interested in receiving the answer key, please complete the Teacher Key Request and Verification Form . We verify that requestors are teachers prior to sending access to the answer keys as we’ve had many students try to pass as teachers to gain access.

Supported NGSS Performance Expectations

• 5-ESS2-1: Develop a model using an example to describe ways the geosphere, biosphere, hydrosphere, and/or atmosphere interact.
• MS-ESS2-1: Develop a model to describe the cycling of Earth's materials and the flow of energy that drives this process.
• HS-ESS2-1: Develop a model to illustrate how Earth’s internal and surface processes operate at different spatial and temporal scales to form continental and ocean-floor features.

Learning Objectives

• Students will understand how nitrogen moves between reservoirs and is constantly recycled.
• Students will be able to identify nitrogen reservoirs. 
• Students will understand the importance of nitrogen as it relates to Earth as a system and as it relates to you personally.
• Students will understand that nitrogen travels freely between physical aspects of Earth and living things.

Essential Questions

• What parts of Earth need nitrogen? 

Technology Requirements

• Internet Required
• One-to-One (tablet, laptop, or CPU)
• One-to-a-Group

Complementary Lesson Plans

Air, water, land, & life: a global perspective.

An Earth System View of Earthrise

Interactive Files

My NASA Data Visualization Tool

• Earth System Data Explorer

Related Resources

Download this page, not finding what you are looking for.

This page has been archived and is no longer updated

The Nitrogen Cycle: Processes, Players, and Human Impact

Introduction

Nitrogen is one of the primary nutrients critical for the survival of all living organisms. It is a necessary component of many biomolecules, including proteins, DNA, and chlorophyll. Although nitrogen is very abundant in the atmosphere as dinitrogen gas (N 2 ), it is largely inaccessible in this form to most organisms, making nitrogen a scarce resource and often limiting primary productivity in many ecosystems. Only when nitrogen is converted from dinitrogen gas into ammonia (NH 3 ) does it become available to primary producers, such as plants.

In addition to N 2 and NH 3 , nitrogen exists in many different forms, including both inorganic (e.g., ammonia, nitrate) and organic (e.g., amino and nucleic acids) forms. Thus, nitrogen undergoes many different transformations in the ecosystem, changing from one form to another as organisms use it for growth and, in some cases, energy. The major transformations of nitrogen are nitrogen fixation, nitrification, denitrification, anammox, and ammonification (Figure 1). The transformation of nitrogen into its many oxidation states is key to productivity in the biosphere and is highly dependent on the activities of a diverse assemblage of microorganisms, such as bacteria, archaea, and fungi.

Since the mid-1900s, humans have been exerting an ever-increasing impact on the global nitrogen cycle. Human activities, such as making fertilizers and burning fossil fuels, have significantly altered the amount of fixed nitrogen in the Earth's ecosystems. In fact, some predict that by 2030, the amount of nitrogen fixed by human activities will exceed that fixed by microbial processes (Vitousek 1997). Increases in available nitrogen can alter ecosystems by increasing primary productivity and impacting carbon storage (Galloway et al . 1994). Because of the importance of nitrogen in all ecosystems and the significant impact from human activities, nitrogen and its transformations have received a great deal of attention from ecologists.

Nitrogen Fixation

Nitrogen gas (N 2 ) makes up nearly 80% of the Earth's atmosphere, yet nitrogen is often the nutrient that limits primary production in many ecosystems. Why is this so? Because plants and animals are not able to use nitrogen gas in that form. For nitrogen to be available to make proteins, DNA, and other biologically important compounds, it must first be converted into a different chemical form. The process of converting N 2 into biologically available nitrogen is called nitrogen fixation. N 2 gas is a very stable compound due to the strength of the triple bond between the nitrogen atoms, and it requires a large amount of energy to break this bond. The whole process requires eight electrons and at least sixteen ATP molecules (Figure 2). As a result, only a select group of prokaryotes are able to carry out this energetically demanding process. Although most nitrogen fixation is carried out by prokaryotes, some nitrogen can be fixed abiotically by lightning or certain industrial processes, including the combustion of fossil fuels.

Some of these bacteria are aerobic, others are anaerobic; some are phototrophic, others are chemotrophic (i.e., they use chemicals as their energy source instead of light) (Table 1). Although there is great physiological and phylogenetic diversity among the organisms that carry out nitrogen fixation, they all have a similar enzyme complex called nitrogenase that catalyzes the reduction of N 2 to NH 3 (ammonia), which can be used as a genetic marker to identify the potential for nitrogen fixation. One of the characteristics of nitrogenase is that the enzyme complex is very sensitive to oxygen and is deactivated in its presence. This presents an interesting dilemma for aerobic nitrogen-fixers and particularly for aerobic nitrogen-fixers that are also photosynthetic since they actually produce oxygen. Over time, nitrogen-fixers have evolved different ways to protect their nitrogenase from oxygen. For example, some cyanobacteria have structures called heterocysts that provide a low-oxygen environment for the enzyme and serves as the site where all the nitrogen fixation occurs in these organisms. Other photosynthetic nitrogen-fixers fix nitrogen only at night when their photosystems are dormant and are not producing oxygen.

Genes for nitrogenase are globally distributed and have been found in many aerobic habitats (e.g., oceans, lakes, soils) and also in habitats that may be anaerobic or microaerophilic (e.g., termite guts, sediments, hypersaline lakes, microbial mats, planktonic crustaceans) (Zehr et al . 2003). The broad distribution of nitrogen-fixing genes suggests that nitrogen-fixing organisms display a very broad range of environmental conditions, as might be expected for a process that is critical to the survival of all life on Earth.

Table 1: Representative prokaryotes known to carry out nitrogen fixation © 2010 Nature Education .

Nitrification

Nitrification is the process that converts ammonia to nitrite and then to nitrate and is another important step in the global nitrogen cycle. Most nitrification occurs aerobically and is carried out exclusively by prokaryotes. There are two distinct steps of nitrification that are carried out by distinct types of microorganisms. The first step is the oxidation of ammonia to nitrite, which is carried out by microbes known as ammonia-oxidizers. Aerobic ammonia oxidizers convert ammonia to nitrite via the intermediate hydroxylamine, a process that requires two different enzymes, ammonia monooxygenase and hydroxylamine oxidoreductase (Figure 4). The process generates a very small amount of energy relative to many other types of metabolism; as a result, nitrosofiers are notoriously very slow growers. Additionally, aerobic ammonia oxidizers are also autotrophs, fixing carbon dioxide to produce organic carbon, much like photosynthetic organisms, but using ammonia as the energy source instead of light.

Unlike nitrogen fixation that is carried out by many different kinds of microbes, ammonia oxidation is less broadly distributed among prokaryotes. Until recently, it was thought that all ammonia oxidation was carried out by only a few types of bacteria in the genera Nitrosomonas , Nitrosospira , and Nitrosococcus . However, in 2005 an archaeon was discovered that could also oxidize ammonia (Koenneke et al . 2005). Since their discovery, ammonia-oxidizing Archaea have often been found to outnumber the ammonia-oxidizing Bacteria in many habitats. In the past several years, ammonia-oxidizing Archaea have been found to be abundant in oceans, soils, and salt marshes, suggesting an important role in the nitrogen cycle for these newly-discovered organisms. Currently, only one ammonia-oxidizing archaeon has been grown in pure culture, Nitrosopumilus maritimus , so our understanding of their physiological diversity is limited.

The second step in nitrification is the oxidation of nitrite (NO 2 - ) to nitrate (NO 3 - ) (Figure 5). This step is carried out by a completely separate group of prokaryotes, known as nitrite-oxidizing Bacteria. Some of the genera involved in nitrite oxidation include Nitrospira , Nitrobacter , Nitrococcus , and Nitrospina . Similar to ammonia oxidizers, the energy generated from the oxidation of nitrite to nitrate is very small, and thus growth yields are very low. In fact, ammonia- and nitrite-oxidizers must oxidize many molecules of ammonia or nitrite in order to fix a single molecule of CO 2 . For complete nitrification, both ammonia oxidation and nitrite oxidation must occur.

Ammonia-oxidizers and nitrite-oxidizers are ubiquitous in aerobic environments. They have been extensively studied in natural environments such as soils, estuaries, lakes, and open-ocean environments. However, ammonia- and nitrite-oxidizers also play a very important role in wastewater treatment facilities by removing potentially harmful levels of ammonium that could lead to the pollution of the receiving waters. Much research has focused on how to maintain stable populations of these important microbes in wastewater treatment plants. Additionally, ammonia- and nitrite-oxidizers help to maintain healthy aquaria by facilitating the removal of potentially toxic ammonium excreted in fish urine.

Traditionally, all nitrification was thought to be carried out under aerobic conditions, but recently a new type of ammonia oxidation occurring under anoxic conditions was discovered (Strous et al . 1999). Anammox (anaerobic ammonia oxidation) is carried out by prokaryotes belonging to the Planctomycetes phylum of Bacteria. The first described anammox bacterium was Brocadia anammoxidans . Anammox bacteria oxidize ammonia by using nitrite as the electron acceptor to produce gaseous nitrogen (Figure 6). Anammox bacteria were first discovered in anoxic bioreactors of wasterwater treatment plants but have since been found in a variety of aquatic systems, including low-oxygen zones of the ocean, coastal and estuarine sediments, mangroves, and freshwater lakes. In some areas of the ocean, the anammox process is considered to be responsible for a significant loss of nitrogen (Kuypers et al . 2005). However, Ward et al . (2009) argue that denitrification rather than anammox is responsible for most nitrogen loss in other areas. Whether anammox or denitrification is responsible for most nitrogen loss in the ocean, it is clear that anammox represents an important process in the global nitrogen cycle.

Denitrification

Denitrification is the process that converts nitrate to nitrogen gas, thus removing bioavailable nitrogen and returning it to the atmosphere. Dinitrogen gas (N 2 ) is the ultimate end product of denitrification, but other intermediate gaseous forms of nitrogen exist (Figure 7). Some of these gases, such as nitrous oxide (N 2 O), are considered greenhouse gasses, reacting with ozone and contributing to air pollution.

Unlike nitrification, denitrification is an anaerobic process, occurring mostly in soils and sediments and anoxic zones in lakes and oceans. Similar to nitrogen fixation, denitrification is carried out by a diverse group of prokaryotes, and there is recent evidence that some eukaryotes are also capable of denitrification (Risgaard-Petersen et al . 2006). Some denitrifying bacteria include species in the genera Bacillus , Paracoccus , and Pseudomonas . Denitrifiers are chemoorganotrophs and thus must also be supplied with some form of organic carbon.

Denitrification is important in that it removes fixed nitrogen (i.e., nitrate) from the ecosystem and returns it to the atmosphere in a biologically inert form (N 2 ). This is particularly important in agriculture where the loss of nitrates in fertilizer is detrimental and costly. However, denitrification in wastewater treatment plays a very beneficial role by removing unwanted nitrates from the wastewater effluent, thereby reducing the chances that the water discharged from the treatment plants will cause undesirable consequences (e.g., algal blooms).

Ammonification

When an organism excretes waste or dies, the nitrogen in its tissues is in the form of organic nitrogen (e.g. amino acids, DNA). Various fungi and prokaryotes then decompose the tissue and release inorganic nitrogen back into the ecosystem as ammonia in the process known as ammonification. The ammonia then becomes available for uptake by plants and other microorganisms for growth.

Ecological Implications of Human Alterations to the Nitrogen Cycle

Many human activities have a significant impact on the nitrogen cycle. Burning fossil fuels, application of nitrogen-based fertilizers, and other activities can dramatically increase the amount of biologically available nitrogen in an ecosystem. And because nitrogen availability often limits the primary productivity of many ecosystems, large changes in the availability of nitrogen can lead to severe alterations of the nitrogen cycle in both aquatic and terrestrial ecosystems. Industrial nitrogen fixation has increased exponentially since the 1940s, and human activity has doubled the amount of global nitrogen fixation (Vitousek et al . 1997).

In terrestrial ecosystems, the addition of nitrogen can lead to nutrient imbalance in trees, changes in forest health, and declines in biodiversity. With increased nitrogen availability there is often a change in carbon storage, thus impacting more processes than just the nitrogen cycle. In agricultural systems, fertilizers are used extensively to increase plant production, but unused nitrogen, usually in the form of nitrate, can leach out of the soil, enter streams and rivers, and ultimately make its way into our drinking water. The process of making synthetic fertilizers for use in agriculture by causing N 2 to react with H 2 , known as the Haber-Bosch process, has increased significantly over the past several decades. In fact, today, nearly 80% of the nitrogen found in human tissues originated from the Haber-Bosch process (Howarth 2008).

Much of the nitrogen applied to agricultural and urban areas ultimately enters rivers and nearshore coastal systems. In nearshore marine systems, increases in nitrogen can often lead to anoxia (no oxygen) or hypoxia (low oxygen), altered biodiversity, changes in food-web structure, and general habitat degradation. One common consequence of increased nitrogen is an increase in harmful algal blooms (Howarth 2008). Toxic blooms of certain types of dinoflagellates have been associated with high fish and shellfish mortality in some areas. Even without such economically catastrophic effects, the addition of nitrogen can lead to changes in biodiversity and species composition that may lead to changes in overall ecosystem function. Some have even suggested that alterations to the nitrogen cycle may lead to an increased risk of parasitic and infectious diseases among humans and wildlife (Johnson et al . 2010). Additionally, increases in nitrogen in aquatic systems can lead to increased acidification in freshwater ecosystems.

Nitrogen is arguably the most important nutrient in regulating primary productivity and species diversity in both aquatic and terrestrial ecosystems (Vitousek et al . 2002). Microbially-driven processes such as nitrogen fixation, nitrification, and denitrification, constitute the bulk of nitrogen transformations, and play a critical role in the fate of nitrogen in the Earth's ecosystems. However, as human populations continue to increase, the consequences of human activities continue to threaten our resources and have already significantly altered the global nitrogen cycle.

References and Recommended Reading

Galloway, J. N. et al . Year 2020: Consequences of population growth and development on deposition of oxidized nitrogen. Ambio 23 , 120–123 (1994).

Howarth, R. W. Coastal nitrogen pollution: a review of sources and trends globally and regionally. Harmful Algae 8 , 14–20. (2008).

Johnson, P. T. J. et al. Linking environmental nutrient enrichment and disease emergence in humans and wildlife. Ecological Applications 20 , 16–29 (2010).

Koenneke, M. et al. Isolation of an autotrophic ammonia-oxidizing marine archaeon. Nature 437 , 543–546 (2005).

Kuypers, M. M. M. et al. Massive nitrogen loss from the Benguela upwelling system through anaerobic ammonium oxidation. Proceedings of the National Academy of Sciences of the United States of America 102 , 6478–6483 (2005).

Risgaard-Petersen, N. et al. Evidence for complete denitrification in a benthic foraminifer. Nature 443 , 93–96 (2006).

Strous, M. et al. Missing lithotroph identified as new planctomycete. Nature 400 , 446–449 (1999).

Vitousek, P. M. et al. Human alteration of the global nitrogen cycle: sources and consequences. Ecological Applications 7 , 737–750 (1997).

Vitousek, P. M. et al. Towards an ecological understanding of biological nitrogen fixation. Biogeochemistry 57 , 1–45 (2002).

Ward, B. B. et al. Denitrification as the dominant nitrogen loss process in the Arabian Sea. Nature 460 , 78–81 (2009).

Article History

Flag inappropriate.

Email your Friend

•  |  Lead Editor: 

Within this Subject (24)

• Basic (13)
• Intermediate (5)
• Advanced (6)

Other Topic Rooms

• Ecosystem Ecology
• Physiological Ecology
• Population Ecology
• Community Ecology
• Global and Regional Ecology
• Conservation and Restoration
• Animal Behavior
• Teach Ecology
• Earth's Climate: Past, Present, and Future
• Terrestrial Geosystems
• Marine Geosystems
• Scientific Underpinnings
• Paleontology and Primate Evolution
• Human Fossil Record
• The Living Primates

© 2014 Nature Education

• Press Room |
• Terms of Use |
• Privacy Notice |

Visual Browse

5 Creative Ways to Teach Nitrogen Cycle Without Lecturing

The biogeochemical cycles are fascinating natural processes that allow for the rotation of essential nutrients and elements between living and non-living components of the ecosystem. The Nitrogen cycle, in particular, is a critical element of this cycle. 

The fact that nitrogen makes up 78% of our atmosphere and plays a crucial role in DNA and protein structures comes as an inspiration for students to learn more about this wonderful element. 

While we understand that the topic is a data-rich one, we can’t underestimate its importance and ignore it. Hence, as an initiative to make lectures seamless and more interactive, we list 5 creative ways that educators can use to teach the nitrogen cycle in their next sessions.

1. Use Interactive Models and Simulations

Interactive physical and virtual models are effective tools for teaching the nitrogen cycle as they provide a visual reference that students can refer back to throughout their learning. Barbara Lachenbruch reports in her study that the use of such instructor-made models can facilitate and motivate other instructors to develop their appropriate models and student-engaging activities for teaching the essence of any topic.

Built on the same idea, Labster provides an interactive virtual model where students can assume the role of a food producer and manage the various parameters of food production while linking it to the nitrogen cycle. 

Discover Labster's Nitrogen Cycle virtual lab today!

3. Learning with Games and Activities

Games and activities can be an engaging and effective way to teach about the nitrogen cycle. Educators can include different types of lab activities and hands-on experiments that can help deliver the ideas and concepts of the nitrogen cycle.

• Nitrogen Fixation Experiment (students can grow legumes in different soil types and see for themselves how the process of nitrogen fixation happens)
• Nitrogen Cycle Water Quality Test (students use testing kits to analyze the quality of water in a local pond or stream for nitrogen content)  

These lab activities can help to reinforce key concepts related to the nitrogen cycle. To further simplify the organization of these activities, Labster has designed an activity room where all of these hands-on experiments can be readily tried by your students.

3. Infusing Technology into Study Plans

With technology at our fingertips, educators can create a dynamic and immersive learning experience that will captivate students and inspire a love for science and the natural world.  Interactive multimedia options can be integrated into lesson plans to bring the nitrogen cycle to life for students. 

Labster’s Nitrogen Cycle Simulation allows students to differentiate between different stages of the cycle while also exploring the impact of various human activities on the cycle. 

As students can work at their own pace and explore the simulation in ways that are meaningful to them, it becomes a favorable choice for most learners.

4. Inspiring Learners by Connecting to Career Prospects

Linking a scientific concept to its importance in the job market makes it lucrative for students to master. You can engage your students with a unique perspective on the nitrogen cycle by introducing them to its prospects in agronomy, soil science, biogeochemistry, and microbiology. 

Inviting experts from different domains to share and discuss how different aspects of the nitrogen cycle are important for their work can be another big motivator. Taking your students on field trips to local farms, research institutions, or water treatment facilities to observe how nitrogen management impacts these industries can also be a great way to initiate them into learning this topic.  

Alternatively, you can take your students on a virtual field trip where they can witness for themselves the impact of the overexploitation of synthetic fertilizers, their link to the nitrogen cycle, and the menace of subsequent aquatic pollution.

5. Connecting the Topic to Real-World Applications

Highlighting the importance of the nitrogen cycle in sustaining life by connecting it to real-world issues like food production, water quality, and climate change can be a great way to gather students’ interests. Some of the ideas to do so are:

• Discuss the role of human activities in disrupting the nitrogen cycle and the potential consequences for ecosystems and the planet. 
• Encourage students to brainstorm solutions to mitigate these problems and participate in local environmental initiatives that promote a balanced nitrogen cycle.

Final thoughts

Making the nitrogen cycle an interesting topic for students might be a task but with current technological advancements and crisp Labster’s Nitrogen Cycle Simulation , educators can inspire the next generation of scientists and environmentalists to work towards creating a sustainable future for our planet.

Living in these times where Earth’s health is constantly degrading, the next generation should be sensitized more towards critical geochemical processes like the nitrogen cycle.  

• Lachenbruch, B. (2011). Physical models as an aid for teaching wood anatomy. IAWA journal, 32(3), 301-312.

Labster helps universities and high schools enhance student success in STEM.

Explore More

Introducing Math for Scientists: Empower Students with Essential Math Skills for Scientific Success

In Their Own Words: Students Weigh in on Labster’s Impact

Accessibility Support Across the Spectrum

Discover The Most Immersive Digital Learning Platform.

Request a demo to discover how Labster helps high schools and universities enhance student success.