4th PeriodThe Nitrogen Cycle

Master the nitrogen cycle! Biology worksheet covers fixation, ammonification, and more.

All of the organisms in the circles represent important parts of the nitrogen cycle. What are they called? Plants Animals Bacteria Decomposers What is the name of the cycle below? Water Cycle Carbon Cycle Nitrogen Cycle Phosphorous Cycle Matching Match the term with the correct definition. Read carefully and use the picture above to help. decomposers break down waste and dead organisms (bacteria and fungi) nitrogen fixing bacteria changes nitrogen from the air (N2) into different compounds nitrifying bacteria changes the different nitrogen compounds into forms that plants can use denitrifying bacteria breaks down and returns nitrogen compounds to the air legumes plants like peas and beans that have nitrogen-fixing bacteria in their roots The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmosphere, terrestrial, and marine ecosystems. The conversion of nitrogen can be carried out through both biological and physical processes. The biological processes involve plants and specialized bacteria, while the physical process involves lightning. Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification.The majority of Earth's atmosphere (78%) is atmospheric nitrogen, making it the largest source of nitrogen. However, atmospheric nitrogen can't be used by most plants and animals the way it is, which is why the nitrogen cycle is so important. The nitrogen cycle is of particular interest to ecologists because nitrogen availability can affect the rate of key ecosystem processes, including primary production (plants) and decomposition. Human activities such as fossil fuel combustion, use of artificial nitrogen fertilizers, and release of nitrogen in wastewater have dramatically altered the global nitrogen cycle. Read the following paragraph and use the information to answerquestions 1-5. The Nitrogen CycleAll organisms need nitrogen to make proteins and nucleic acid. Nucleic acids are DNA and RNA. The complex pathway that nitrogen follows within the ecosystem is called the nitrogen cycle. However, most plants can use nitrogen only in the form of nitrate. The process of converting nitrogen gas in to nitrate is called nitrogen fixation. Organisms rely on the actions of nitrogen fixing bacteria that are able to transform nitrogen gas into a usable form. Nitrogen-fixing bacteria live in the soil in the roots of some plants, such as beans, peas, clover, and alfalfa. 1. All organisms need _ to make proteins and amino acids. nitrogen oxygen carbon phosphorous 2. What is the complex pathway that nitrogen follows within the ecosystem is called? The Carbon Cycle The Phosphorous Cycle The Nitrogen Cycle The DNA Cycle 3. Most plants can only use nitrogen in what form? nitrum nitrous pure nitrogen nitrate 4. What is the process of converting nitrogen gas into nitrate called? Nitrogen Conversion Nitrogen Reaction Nitrogen Respiration Nitrogen Fixation 5. Where do nitrogen-fixing bacteria live? in the air in the soil, in the roots of plants in the soil, in the leaves of plants in animals Read the following paragraph and use the information to answer questions 6-11. Decomposers break down dead and decaying organisms and release the nitrogen they contain as ammonia (NH3). When ammonia is in the soil it becomes ammonium (NH4+). This process is known as ammonification. Through ammonification, nitrogen that would otherwise be lost is reintroduced into the ecosystem.Bacteria in the soil take up the ammonium and react it with oxygen to form nitrites (NO2-), and nitrates (NO3-). This process is called nitrification. The erosion of nitrate-rich rocks also releases nitrates into an ecosystem. Plants use nitrates to form amino acids. Nitrogen is returned to the atmosphere through denitrification. Denitrification occurs when anaerobic bacteria, which are bacteria that can live both with and without oxygen, break down nitrates and release nitrogen back into the atmosphere. 6. When decomposers break down dead and decaying organisms and release the nitrogen they contain, what is it released as? ammonium ammonia ammonide ammonous 7. What does ammonia become when it is in the soil? ammonium ammonia ammonide ammonous 8. What is the process of NH3 becoming NH4+ is called? nitricication ammonification notification ammonia transfer 9. Bacteria in the soil takes up ammonium and react it with _ to form nitrate and nitrites. carbon nitrogen oxygen fluorine 10. Which is nitrification? bacteria in the soil take up the phosphorous and react it with carbon to from nitrites and nitrates bacteria in the soil take up the phosphorous and react it with carbon to from oxites and oxates bacteria in the soil take up the ammonium and react it with oxygen to from oxites and oxates bacteria in the soil take up the ammonium and react it with oxygen to from nitrites and nitrates. 11. What are anaerobic bacteria? bacteria that can live with oxygen bacteria that die in oxygen bacteria that can live without oxygen bacteria that can live with and without oxygen