Nitrogen Cycle
Like water and carbon, nitrogen is continuously recycled through the biosphere in a process called the nitrogen cycle, moving nitrogen between the atmosphere, soil, plants, and animals.
Although nitrogen gas makes up 78% of Earth’s atmosphere, it must be converted into usable forms for plants and animals to take up, which involves several steps.
The nitrogen cycle begins with nitrogen fixation, a process in which special bacteria in the soil and plant roots turn nitrogen gas into ammonia, which plants can absorb.
Next, two different types of bacteria convert ammonia into nitrates through a process called nitrification. Plants absorb nitrates through their roots, turning them into organic compounds that animals consume.
When plants and animals die or release waste, decomposer bacteria break down their remains. This process, called ammonification, converts nitrogen back into ammonia, returning it to the soil.
The final step in the cycle is denitrification. In this process, specific bacteria convert nitrates back into nitrogen gas, releasing it into the atmosphere and completing the cycle.
Nitrogen Cycle
The nitrogen cycle is the process by which nitrogen moves through the air, soil, water, and living organisms. Nitrogen is essential for life because it is a major part of proteins and DNA. Although nitrogen gas makes up most of the atmosphere, it must be converted into usable forms by certain bacteria through a process called nitrogen fixation. Plants absorb these compounds, and animals get nitrogen by eating plants or other animals. Decomposers and bacteria return nitrogen to the soil and atmosphere, completing the cycle. The nitrogen cycle illustrates the movement of matter within ecosystems, a fundamental process that sustains all life forms.
Science and Engineering Practices (SEP): Developing and Using Models
Scientists develop and use models to describe how nitrogen cycles through ecosystems. These models help show how nitrogen changes form and moves through the atmosphere, soil, and organisms. By using diagrams or digital simulations, scientists can better understand how nitrogen is transformed and transferred across components of the environment.
Activity Ideas:
- Nitrogen cycle diagram – Create a labeled diagram that includes nitrogen fixation, plant uptake, animal consumption, decomposition, and denitrification.
- Role-play the nitrogen cycle – Assign roles (e.g., nitrogen-fixing bacteria, plants, animals, decomposers) and act out how nitrogen moves through the cycle.
- Real-world case study – Analyze the effects of nitrogen pollution from agriculture on local ecosystems.
By modeling the nitrogen cycle, we can gain a clearer understanding of how matter cycles through the environment.
Crosscutting Concept (CCC): Energy and Matter
The nitrogen cycle demonstrates how matter is transferred and transformed through ecosystems, and how these processes are powered by the flow of energy.
- Transfer: Nitrogen moves between the atmosphere, soil, and organisms.
Effect: This transfer ensures nitrogen is available for life processes such as growth and reproduction. - Transformation: Bacteria and decomposers change nitrogen into different chemical forms.
Effect: These changes allow plants to absorb nitrogen and keep it circulating in ecosystems. - Recycling: Nitrogen is continuously cycled and reused in natural systems.
Effect: It supports the long-term sustainability of ecosystems.
Like water and carbon, nitrogen is continuously recycled through the biosphere in a process called the nitrogen cycle, moving nitrogen between the atmosphere, soil, plants, and animals.
Although nitrogen gas makes up 78% of Earth’s atmosphere, it must be converted into usable forms for plants and animals to take up, which involves several steps.
The nitrogen cycle begins with nitrogen fixation, a process in which special bacteria in the soil and plant roots turn nitrogen gas into ammonia, which plants can absorb.
Next, two different types of bacteria convert ammonia into nitrates through a process called nitrification. Plants absorb nitrates through their roots, turning them into organic compounds that animals consume.
When plants and animals die or release waste, decomposer bacteria break down their remains. This process, called ammonification, converts nitrogen back into ammonia, returning it to the soil.
The final step in the cycle is denitrification. In this process, specific bacteria convert nitrates back into nitrogen gas, releasing it into the atmosphere and completing the cycle.
Like water and carbon, nitrogen is continuously recycled through the biosphere in a process called the nitrogen cycle, moving nitrogen between the atmosphere, soil, plants, and animals.
Although nitrogen gas makes up 78% of Earth’s atmosphere, it must be converted into usable forms for plants and animals to take up, which involves several steps.
The nitrogen cycle begins with nitrogen fixation, a process in which special bacteria in the soil and plant roots turn nitrogen gas into ammonia, which plants can absorb.
Next, two different types of bacteria convert ammonia into nitrates through a process called nitrification. Plants absorb nitrates through their roots, turning them into organic compounds that animals consume.
When plants and animals die or release waste, decomposer bacteria break down their remains. This process, called ammonification, converts nitrogen back into ammonia, returning it to the soil.
The final step in the cycle is denitrification. In this process, specific bacteria convert nitrates back into nitrogen gas, releasing it into the atmosphere and completing the cycle.
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