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Nutrient cycles

Organisms rely on nutrients in order to survive. These include carbon, oxygen, nitrogen, water and mineral salts.

These nutrients need to be cycled through the ecosystem so that they can be re- used. This is called nutrient recycling . In biology, this is the movement of nutrients from the physical environment into living organisms and back into the environment. The flow of energy you sawbefore from the sun to herbivores and then to carnivores is part of this process. In any environment the flow of nutrients must be stable and balancedso that organisms can survive. If the cycle stops at any point, nutrients will become locked in place and cannot be used in the next step.

The water cycle, carbon cycle, oxygen cycle and nitrogen cycle are examples of nutrient re-cycling.

Video: (External Link)

Here is a simple video explaining nutrient cycling


(ex (External Link) )

The earth is sometimes known as the "water planet" because over 70 percent of its surface is covered by water. All living organisms need water for theirsurvival.

In this cycle, water is transported between water reservoirs in the environment and living organisms. This happens through these processes:

  • Liquid water in oceans and lakes is converted to water vapour by evaporation . This is caused by heating of the water by the sun. The water vapour rises into the atmosphere.
  • Plants release water into the air as vapour during photosynthesis, this is called transpiration .
  • When water vapour in the atmosphere cools, it can transform into tiny droplets of liquid water to form clouds by the process of condensation
  • When condensed water droplets grow so large that the air can no longer support them against the pull of gravity, they fall to the earth through precipitation . If the water droplets fall as liquid, it is called rain. If the temperature of the surrounding air is cold enough to freeze the water droplets, then the waterfalls as snow, sleet or hail.
  • Water that falls onto the earth runs into lakes, rivers or oceans.
(image source: (External Link) )The Water Cycle.

Animation: (External Link)

This is an animation of the water cycle


Oxygen is one of the main gases found in the air, along with nitrogen.

Oxygen is re-cycled between the air and living organisms in the following ways:

  • Organisms take in oxygen during respiration , which they use for cellular processes to break down energy rich nutrients.
  • When wood or fossil fuels burn, they consume oxygen and release carbon dioxide and water into the atmosphere through combustion .
  • Plants release oxygen into the air as a by-product of photosynthesis .

Because animals trap oxygen during respiration, the release of oxygen by plants during photosynthesis is the main way oxygen is released into the atmosphere.

(image source: (External Link) )The Oxygen Cycle.

Video: (External Link)

This is a video explaining the oxygen cycle


Carbon is the basic building block of all organic materials, and therefore, of living organisms. Most of the carbon on earth can be found in the crust. Otherreservoirs of carbon include the oceans and atmosphere.

Carbon moves from one reservoir to another by these processes:

  • Combustion of wood and fossil fuels transfers carbon to the atmosphere as carbon dioxide.
  • Carbon dioxide is taken up by plants during photosynthesis and gets converted into energy rich sources, such as glucose, that contain carbon.
  • Animals eat plants for food, taking up the carbon. They release carbon into the atmosphere as carbon dioxide during respiration .
  • Organisms convert carbon into organic molecules like fats, carbohydrates and proteins when they eat plants or animals.
  • Carbon dioxide in the atmosphere can also precipitate as carbonate in ocean sediments. These ocean sediments are melted by the movement of tectonic plates and then returned to the surface during volcanicactivity.
  • Carbon dioxide gas is released into the atmosphere during volcanic eruptions.

Photosynthesis and respiration are the main carbon cycling processes involving living organisms.

(image source: (External Link) )The Carbon Cycle

GAME: (External Link)

This is a game you can play to learn more about the carbon cycle


Nitrogen (N2) makes up most of the gas in the atmosphere (about 78%). Nitrogen is important to living organisms and is used in the production of amino acids,proteins and nucleic acids (DNA, RNA). Only a few single-cell organisms, like bacteria can use nitrogen from the atmosphere directly. For multi-cellularorganisms, like plants and animals, nitrogen has to be changed into other forms, eg. nitrates or ammonia. This process is known as nitrogen fixation .

The nitrogen cycle involves these steps:

During decomposition , bacteria and fungi break down proteins and amino acids from plants and animals into nitrogen in the form of ammonia (NH3) by the process of ammonification and convert the ammonia to nitrate (NO3-) by nitrification .

Nitrogen can be changed to nitrates directly by lightning . The rapid growth of fungi and algae after thunderstorms is because of this process, which increases the amount of nitrates that fall onto the earth inrain water, acting as fertilizer.

Ammonia and nitrates are absorbed by plants through their roots.

Humans and animals get their nitrogen supplies by eating plants or plant-eating animals.

The nitrogen is returned to the cycle when bacteria decompose the waste or dead bodies of these higher organisms, and in the process, convert organic nitrogen into ammonia.

In a process called denitrification , other bacteria convert ammonia and nitrate into nitrogen and nitrous oxide (N 2 O). Nitrogen is returned to the atmosphere to start the cycle over again.

The Nitrogen Cycle

SIMULATION: http://www.teachersdomain.org/asset/lsps07_int_nitrogen/

You can play with this simulation to learn more about the Nitrogen cycle.


Here are some animations of the nitrogen cycle:

(External Link)

(External Link)

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
ya I also want to know the raman spectra
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
yes that's correct
I think
Nasa has use it in the 60's, copper as water purification in the moon travel.
nanocopper obvius
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
analytical skills graphene is prepared to kill any type viruses .
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
why and for what was five kingdom of classification of organisms introduced
give the ans as fast as possible
Comment on the ozone depletion over the period of 1982 to 1996
Mpho Reply

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Source:  OpenStax, Siyavula: life sciences grade 10. OpenStax CNX. Apr 11, 2012 Download for free at http://cnx.org/content/col11410/1.3
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