THE NITROGEN CYCLE

Nitrogen makes up 78% of our atmosphere and is important to all living things

Nitrogen is an important element in ecosystems. It makes up almost 80% of Earth’s atmosphere and is required by organisms to make proteins. Atmospheric nitrogen cannot be used by living things so it must be converted into usable forms. The nitrogen cycle is the movement of nitrogen through the food chain from simple inorganic (not made from living things) compounds into complex organic (made from living things) compounds.

The Nitrogen Cycle Introduction

Use the information below and on the following slides to help you fill out p. 43 in your journal. Raise your hand if you have any questions along the way!

IMPORTANT WORDS TO KNOW

NITROGEN: gas in the air (N2)

AMMONIA: NH3 (a compound of nitrogen and hydrogen)

NITRATES: NO3 (a compound of nitrogen and oxygen)

***Ammonia and Nitrates are usable forms of nitrogen for plants and animals

There are 5 main steps to the Nitrogen Cycle

1. Nitrogen Fixation
2. Ammonification
3. Nitrification
4. Assimilation
5. Denitrification

Nitrogen Fixation

• Plants cannot use Nitrogen in its gas form from the atmosphere so it must be transformed first

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• During Nitrogen fixation, Bacteria transform nitrogen gas (N2) into ammonia which can be absorbed by plants.

Ammonification

• Decomposers like bacteria transform the nitrogen-containing parts of the organic matter (dead organisms and waste) into ammonia

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Nitrification

Bacteria transform ammonia into nitrates (NO3) which plants can absorb

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Assimilation

The process by which plants absorb ammonia or nitrates through their roots to make proteins

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**animals get nitrates through eating the plants

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Denitrification

Some bacteria convert nitrates in the soil to nitrogen gas which is released into the atmosphere

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Humans influence the nitrogen cycle negatively

1. Fertilizers: contain nitrates. If excess nitrates get into water environments, it can kill algae which decreases the amount of oxygen there

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• Fossil Fuels: burning fossil fuels release nitrous oxide (N2O) which can form acid rain. Acid rain can damage plants and aquatic ecosystems

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Summary of the Nitrogen Cycle

• Bacteria transforms nitrogen gas into a usable form for plants called ammonia and nitrates
• Plants absorb the nitrates
• Animals get nitrogen from eating plants
• When plants and animals die or excrete waste, decomposers (like bacteria), release nitrogen gas back into the atmosphere

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See the cycle in Action !

Click on the link below to see it in action!

https://www.classzone.com/books/ml_science_share/vis_sim/em05_pg20_nitrogen/em05_pg20_nitrogen.swf

Reflections and Conclusions

Click the google form link below to answer a few reflection questions about the Nitrogen Cycle

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https://docs.google.com/a/harmonytx.org/forms/d/1PYydgCy7E6F_7w_4VuoY7UArHU-BYNg77-OFUyEQloY/viewform?usp=send_form