<< Chapter < Page Chapter >> Page >

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

find the 15th term of the geometric sequince whose first is 18 and last term of 387
Jerwin Reply
The given of f(x=x-2. then what is the value of this f(3) 5f(x+1)
virgelyn Reply
hmm well what is the answer
how do they get the third part x = (32)5/4
kinnecy Reply
can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
okay, so you have 6 raised to the power of 2. what is that part of your answer
I don't understand what the A with approx sign and the boxed x mean
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
I'm not sure why it wrote it the other way
I got X =-6
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
is it a question of log
Commplementary angles
Idrissa Reply
im all ears I need to learn
right! what he said ⤴⤴⤴
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
kkk nice
Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Comment on the ozone depletion over the period of 1982 to 1996
Mpho Reply

Get the best Algebra and trigonometry course in your pocket!

Source:  OpenStax, Siyavula: life sciences grade 10. OpenStax CNX. Apr 11, 2012 Download for free at http://cnx.org/content/col11410/1.3
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Siyavula: life sciences grade 10' conversation and receive update notifications?