Nitrogen Cycle & How Do Human Activities Affect the Ecosystem by Divine Garcia
Report By: Divine D. Garcia
Symbol: N Atomic No: 7 Atomic Weight: 14.0067
Gas: colorless, odorless and generally inert
Liquid: colorless, and odorless
A gas that made up 79 % of the gases in the atmosphere.
Its compounds are vital components of foods, fertilizers,
Organisms use nitrogen to build proteins and nucleic
Is the cycling of nitrogen between living organisms
and their environment.
Is the process of converting nitrogen into compounds
that can be used by plants and animals.
Is a complex process with four important stages:
Is when the nitrogen gets “fixed” and combines
with oxygen or hydrogen.
There are 3 Ways that Nitrogen gets “fixed”:
(5 % - 8 %)
apart and combines
with oxygen forming
nitrogen oxides (N₂O).
Nitrogen oxides dissolve
in rain, forming nitrates.
Nitrates (NO₃) are carried
to the ground with the rain.
Under great pressure, at a
temperature of 600 C˚, and
with the use of catalyst,
atmospheric nitrogen (N₂)
and hydrogen are combined
to form ammonia (NH₃).
Ammonia can be used as
Some symbiotic bacteria (most often associated
with leguminous plants) and some free-living
bacteria are able to fix nitrogen as organic
Bacteria decomposers break down amino acids from
dead animals and wastes into nitrogen ammonium.
Because plants cannot use the organic forms of
nitrogen that are in the soil as a result of:
wastes ( manure and sewage)
compost and decomposing roots and leaves
Microorganisms convert the organic nitrogen to
ammonium. The ammonium is either taken up by the
plants or is absorbed into the soil particles.
Ammonium (NH₄) in the soil is stored up to later be
changed into inorganic nitrogen, the kind of nitrogen
that most plants can used.
Nitrifying bacteria in the ground first combine
ammonia with oxygen to form nitrites. Then another
group of nitrifying bacteria convert nitrites to nitrates
which green plants can absorb and use.
Converts nitrates (NO₃) in the soil to atmospheric
nitrogen (N₂) replenishing atmosphere.
Other ways that nitrogen returns to the atmosphere:
Humans are top consumers in many food pyramids.
To increase food production, they use methods that
have an effect on food webs.
Monoculture – is the cultivation of a single crop in
large areas. Vast tracts of land are converted to rice
farms, sugar farms, and coconut farms.
Herbicides and Insecticides – farmers spray their
crops with insecticides to kill insect pests, and with
herbicides to kill weeds. However, the chemicals also
destroy other organisms, including beneficial insects
and soil organisms which help in decay.
Chemical Fertilizers – monocrops usually require
large amounts of chemical fertilizers. Continuous and
uncontrolled used of chemical fertilizers may increase
soil acidity, thus destroying soil structure. Findings
show that more fertilizers are needed for the same
amount of yield after years of monoculture.
Fertilizers in the water will cause increased growth of
algae and other plants. They cover the water’s surface
and block the passage of oxygen. Thus, less oxygen is
dissolved in water. Furthermore, when algae and
aquatic plants die, decay microorganism use oxygen.
Dissolved oxygen becomes insufficient, causing fish
and other aquatic animals to die.
To conserve the environment, some desirable
practices are described below:
Grow a variety of crops instead of only one crop.
Use insects to fight other insects (known as biological
control of insect pests).
Instead of chemical fertilizers, try organic farming
using natural fertilizers for crops. Some natural
fertilizers are compost and animal manure.