Name: nitrogen in soil and living things
Uploaded: 2019-03-11T09:21:40.000Z
Duration: 1 min 49 s
Channel: JoVE

K12 Standards

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NC K-12 Science Standard Course of Study

9-12

Biology

ecosystems-interactions-energy-and-dynamics

Ecosystems- Interactions, Energy, and Dynamics

LS.Bio.4.1

The Nitrogen Cycle

窒素循環は生態系において 生物成分と非生物成分間の 窒素元素の動きを表しています 生態系の窒素のほとんどは、大気中の 窒素ガスN2として存在しています ですが、バクテリアだけが必要な酵素を持ち 窒素ガスを他の有機物も使える形に変化させます これを窒素固定といいます つまり、窒素は生態系の中では 非常に限られた栄養となっているのです 土の中のバクテリアが窒素をアンモニアに変えると 植物は窒素をタンパク質 DNAやその他の有機分子に変えることができます それを食べた草食動物によって アミノ酸へと変化するのです アミノ酸はタンパク質へと再合成され 成長や発達、捕食者の栄養となるのです 同時に、草食動物や捕食者は 老廃物として窒素を土に還します 死んだ有機物や老廃物には、どちらも タンパク質、尿素、尿酸の形で窒素があります バクテリアや菌類のような分解者は そうした分子を分解し、アンモニアを土へと還します アンモニアは、やがて植物に吸収されるか 硝化バクテリアによって硝酸塩になります こうした硝酸塩は、植物に吸収されるか 酸素がなければ、脱窒菌によって 窒素ガスに変わります 人間も農業肥料を使うことで 生態系に窒素を出しています ですが、時期を間違えたり、大量に使うと 増えすぎた窒素は、水生生態系へと流れ込み バクテリアを増やし、藻類や 水生植物が繁殖し、富栄養化が起こります

「生態系における窒素源と循環、および大気、水、土壌汚染におけるその役割:批判的レビュー」 Journal of Pollution Effects & Control 03, no. 02 (2015).[<a href="https://doi.org/10.4172/2375-4397.1000136" target="__blank">ソース</a>]

窒素循環

すべてのタンパク質やDNAに存在する窒素原子は、生態系の非生物的な構成要素と生物的な構成要素の間でリサイクルされています。しかし、地球上の窒素の主な形態は窒素ガスであり、ほとんどの動物や植物はこれを利用することができません。そのため、窒素ガスを他の生物に循環させるためには、まず窒素固定菌によって窒素ガスを利用可能な形に変換する必要があります。人間の農業における窒素を含む肥料や動物の排泄物の使用は、自然の窒素サイクルに大きな影響を与えています。 
 
 <h4>生物学的窒素循環</h4>
 
 私たちが吸っている空気の約78%は窒素ガスです。しかし、このN2という形では、利用できる生物はほとんどいません。窒素は、タンパク質やDNAなど、すべての生物に不可欠な分子を構成しています。大気中の窒素を利用できない多くの生物は、窒素固定原核生物や硝化原核生物の副産物を利用しています。窒素固定は窒素ガス（N2）をアンモニア（NH3）に変換し、硝化はNH<3を亜硝酸塩（NO2-）と硝酸塩（NO3-）に変換します。植物はアンモニアや硝酸塩を直接利用することができ、植物を食べる生物は植物を摂取することで窒素を得ることができます。これらの生物が死ぬと、土壌中の細菌が有機態窒素をアンモニアに変換する「アンモニア化」というプロセスが発生します。その後、好気性細菌が脱窒を行い、アンモニアを窒素ガスに変えて大気中に放出するというサイクルを繰り返しています。
 
 <h4>窒素の吸収源</h4>
 
 窒素を長期的に貯蔵する主な貯蔵庫は、大気中の窒素ガスです。しかし、生態系の中には他にも小さな窒素吸収源があります。窒素は、沼地、海洋堆積物、堆積岩などに比較的長期間にわたって固定されています。しかし、窒素化合物は水に非常に溶けやすいため、堆積岩の風化によって窒素が再び生態系に放出される可能性があります。 
 
 <h4>窒素循環に対する人間の影響</h4>
 
 自然環境では植物の成長に窒素が制限要因となることが多いため、農家は農作物の収穫量を増やすために窒素を肥料として土壌に添加しています。農作物が水生生態系に流出すると、富栄養化や有毒な藻類の不自然な急成長を引き起こします。また、大量の家畜を飼育すると、土壌や地域の水源に含まれる硝酸性廃棄物の量が増加します。

すべてのタンパク質とDNAに存在する窒素原子は、生態系の非生物的要素と生物的要素の間でリサイクルされます。しかし、主な形態は...

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生物学

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生態学

Ecosystems

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KEY TERMS AND CONCEPTS

主要用語と概念

nitrogen in soil and living things

Nitrogen in soil and living things moves through ecosystems in several forms. Nitrogen atoms are found in proteins and DNA. Most animals and plants cannot use nitrogen gas, which is the main form of nitrogen on Earth. Nitrogen must first be changed into a usable form by nitrogen-fixing bacteria before it can move through food webs.

About 78% of the air we breathe is nitrogen gas, but few organisms can use it in that form. Nitrogen fixation changes nitrogen gas (N2) into ammonia (NH3). Nitrification then changes ammonia into nitrites (NO2-) and nitrates (NO3-). Plants can use ammonia and nitrates directly. Plant-eating organisms get nitrogen by eating plants.

When organisms die, soil bacteria break down organic nitrogen and convert it into ammonia. This process is called ammonification. Aerobic bacteria can then carry out denitrification and convert ammonia into nitrogen gas that returns to the atmosphere. That return of nitrogen gas completes the cycle.

The main long-term reservoir for nitrogen is nitrogen gas in the atmosphere. Smaller nitrogen sinks also store nitrogen for long periods. These include swamps, marine sediments, and sedimentary rock. Because nitrogen compounds dissolve easily in water, weathering of sedimentary rock can release nitrogen back into the ecosystem.

Human activity can change the nitrogen cycle. Farmers add nitrogen to soil as fertilizer because nitrogen is often a limiting factor for plant growth in natural environments. This can increase agricultural yield. However, runoff from farms can enter aquatic ecosystems and cause eutrophication, which leads to unnaturally rapid growth of toxic algae species. Large numbers of livestock can also increase the amount of nitric waste in soil and local water sources.

Nitrogen in Soil and Living Things

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Energy Transfer as Biomass Efficiency

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what are biogeochemical cycles?

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the water cycle

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the nitrogen cycle

Nitrogen in soil and living things moves through ecosystems in several forms. Nitrogen atoms are found in proteins and DNA. Most animals and plants cannot use nitrogen gas, which is the main form of nitrogen on Earth. Nitrogen must first be changed into a usable form by nitrogen-fixing bacteria before it can move through food webs. About 78% of the air we breathe is nitrogen gas, but few organisms can use it in that form. Nitrogen fixation changes nitrogen gas (N2) into ammonia (NH3).

the phosphorus cycle

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the sulfur cycle

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Follow nitrogen as it moves from air to soil, plants, and animals, and see how bacteria, fertilizers, and runoff shape the cycle in ecosystems.

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What are Biogeochemical Cycles?

The most common elements in organic molecules, carbon, hydrogen, oxygen, nitrogen, sulfur, and phosphorus, are only available in the ecosystem in limited ...

The Water Cycle

The Earth&rsquo;s hydrosphere includes all of the areas where the storage and movement of water occurs. Since water is the basis of all living processes, ...

The Carbon Cycle

Carbon is the basis of all organic matter on Earth, and is recycled through the ecosystem in two primary processes: one in which carbon is exchanged among ...

Nitrogen atoms, present in all proteins and DNA, are recycled between abiotic and biotic components of the ecosystem. However, the primary form of ...

The Phosphorus Cycle

Unlike carbon, water, and nitrogen, phosphorus is not present in the atmosphere as a gas. Instead, most phosphorus in the ecosystem exists as compounds, ...

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Distribution and Dispersion

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LS.Bio.4.2

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Ecological Succession

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Keystone Species

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Symbiotic relationships are long-term, close interactions between individuals of different species that affect the distribution and abundance of those ...

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When organisms require the same limited resources within an environment, they may have to compete for them. Competition is a net-negative interaction. ...

Predator-Prey Interactions

Predators consume prey for energy. Predators that acquire prey and prey that avoid predation both increase their chances of survival and reproduction ...

Ecological Disturbance

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Use mathematics and computational thinking to explain how interactions between organisms (predator/prey, competition) affect carrying capacity and maintain stability in an ecosystem.

LS.Bio.5.1

What is Biodiversity?

Biodiversity describes the variety of living things at multiple organizational levels: genetic, species and ecosystem diversity. Species diversity ...

Engage in argument from evidence to evaluate various solutions to reduce the impact of human activities on biodiversity and ecosystem health.

LS.Bio.5.2

Analyze the relationships between matter and energy within ecosystems.

Nitrogen in Soil and Living Things

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