nitrification

chemistry

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place in nitrogen cycle

In nitrogen cycle
Nitrification, a process carried out by nitrifying bacteria, transforms soil ammonia into nitrates (NO₃−), which plants can incorporate into their own tissues.
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In atmosphere: Nitrogen budget
In a process called nitrification, or nitrogen fixation, bacteria such as Rhizobium living within nodules on the roots of peas, clover, and other legumes convert diatomic nitrogen gas to ammonia. A small amount of nitrogen is also fixed by lightning. Ammonia may be further transformed by other bacteria into…
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In biosphere: The nitrogen cycle
…through the oxidative process of nitrification. Once nitrogen has been assimilated by plants, it can be converted to organic forms, such as amino acids and proteins. Animals can use only organic nitrogen, which they obtain by consuming plants or other animals. As these organisms die, certain microbes such as detritivores…
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work of Winogradsky

In Sergey Nikolayevich Winogradsky
…the microbial agents responsible for nitrification (the oxidation of ammonium salts to nitrites and nitrites to nitrates). He established two new genera—Nitrosomonas (nitrite formers) and Nitrosococcus ([Nitrobacter] nitrate formers)—for the two new types of microorganisms concerned in the process. He returned to St. Petersburg and worked for the Imperial Institute…
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ecosystem

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How an ecosystem works: Producers, herbivores, and carnivores

ecosystem

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Key People:: Charles Elton; Pierre Dansereau

Related Topics:: population; ecological disturbance; ecological resilience; trophic cascade; biogeochemical cycle

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ecosystem, the complex of living organisms, their physical environment, and all their interrelationships in a particular unit of space.

A brief treatment of ecosystems follows. For full treatment, see biosphere.

An ecosystem can be categorized into its abiotic constituents, including minerals, climate, soil, water, sunlight, and all other nonliving elements, and its biotic constituents, consisting of all its living members. Linking these constituents together are two major forces: the flow of energy through the ecosystem and the cycling of nutrients within the ecosystem. Ecosystems vary in size: some are small enough to be contained within single water droplets while others are large enough to encompass entire landscapes and regions (see biome).

(Read E.O. Wilson’s Britannica essay on mass extinction.)

Energy flow

The fundamental source of energy in almost all ecosystems is radiant energy from the Sun. The energy of sunlight is used by the ecosystem’s autotrophic, or self-sustaining, organisms (that is, those that can make their own food). Consisting largely of green vegetation, these organisms are capable of photosynthesis—i.e., they can use the energy of sunlight to convert carbon dioxide and water into simple, energy-rich carbohydrates. The autotrophs use the energy stored within the simple carbohydrates to produce the more complex organic compounds, such as proteins, lipids, and starches, that maintain the organisms’ life processes. The autotrophic segment of the ecosystem is commonly referred to as the producer level.

Chutes d'Ekom - a waterfall on the Nkam river in the rainforest near Melong, in the western highlands of Cameroon in Africa.

Britannica Quiz

Ecosystems

Organic matter generated by autotrophs directly or indirectly sustains heterotrophic organisms. Heterotrophs are the consumers of the ecosystem; they cannot make their own food. They use, rearrange, and ultimately decompose the complex organic materials built up by the autotrophs. All animals and fungi are heterotrophs, as are most bacteria and many other microorganisms.