Carbon, Water, and Nitrogen Cycle

Learning about these cycles is ghetto AF!

The Carbon Cycle

1. Carbon enters the atmosphere as carbon dioxide from respiration and combustion.

2. Carbon dioxide is absorbed by producers to make carbohydrates in photosynthesis.

3. Animals feed on the plant passing the carbon compounds along the food chain.


We need the Carbon Cycle, because we need the air we need to breathe.

The Water Cycle

1. Evaporation:

Heat from the Sun causes water on Earth (in oceans, lakes etc) to evaporate (turn from liquid into gas) and rise into the sky. This water vapor collects in the sky in the form of clouds.

2. Condensation:

As water vapor in the clouds cools down it becomes water again, this process is called condensation.

3. Precipitation:

Water falls from the sky in the form of rain, snow, hail, or sleet, this process is called precipitation.

4. Collection:

Oceans and lakes collect water that has fallen. Water evaporates into the sky again and the cycle continues.

5. Transpiration:

In a process similar to sweating, plants lose water which is absorbed into the atmosphere much like evaporation. The combination of evaporation and transpiration is known as evapotranspiration.

6. Sublimation:

It is possible for a solid to transform into a gas directly (without becoming a liquid). The most common example of sublimation is dry ice (solid carbon dioxide) which sublimes at normal air temperature. Under certain conditions snow and ice can also sublime.


We need the Water Cycle because without water we wouldn't have life.

The Nitrogen Cycle

1. Ammonification:

Ammonification is a process in which the organic nitrogen of plants and animals after their death is converted to ammonium ions (NH4) by the action of saprotrophic fungi and bacteria. The saprotrophs use the ammonia (NH3) to synthesize their own proteins and other nitrogen-containing organic compounds.

2. Nitrification:

Ammonium ions added to the soil by ammonification, are soon oxidized by a process known as nitrification. It takes place in two stages. In the first stage, ammonium (NH4+) is converted to nitrite (NO2-). This reaction involves the addition of oxygen to ammonia, giving rise to hydroxylamine (NH2OH), which is further oxidized to nitrite.

3. Nitrogen uptake by Plants:

Nitrate (NO3–) formed in the process of nitrification is used by most plants as a mineral metabolite and may be converted by them into amino groups and other nitrogen- containing compounds. Nitrates are also added to the soil through rock dissolution and combination of atmospheric nitrogen with oxygen by lightning (nitrates so formed reach the soil by rain). However, many plants also absorb ammonium from the soil.

4. Fixation of Nitrogen:

The reduction of atmospheric nitrogen (N2) to the ammonium ion (NH+4) is called nitrogen fixation. This process can only be carried out by certain species of bacteria and cyanobacteria (Postgate, 1988). Some of these bacteria are free-living, occurring in soil or water (saprophytic bacteria like Azotobacter and Clostridium ; others exist in symbiotic relationship with plants of the Family Legxuninosae, e.g., nodule bacteria Rhizobium leguminosarum).

5. Denitrification:

It is a process in which the nitrate ion (NO3) is reduced to nitrogen dioxide (NO2), di-nitrogen oxide (N2O), nitrogen monoxide (NO) or nitrogen (N2) by certain soil bacteria like Pseudomonas denitrificans. Thus, nitrogen is liberated into the atmosphere. Plants also lose small amounts of nitrogen to the atmosphere as gaseous ammonia, N2O, NO2 and NO especially when well fertilized with nitrogen. Thus, nitrogen cycle depends upon at least four different kinds of bacteria known as the decay causers, the nitrifies, the denitrifiers, and the nitrogen-fixers and there is a regular circulation of nitrogen through the air, soil, plants and animals.


We need the Nitrogen Cycle so things can decompose and become part of the earth.