Biocycles

Water Cycle

Nitrogen Cycle

Why Nitrogen? The Nitrogen cycle is important because nitrogen is an essential element involved in protein synthesis.

Why a cycle? Atmospheric Nitrogen N2(approx. 78% of the earth’s atmosphere) is not directly accessible to most plants or animals.

To NO2- (nitrites) which are still relatively inaccessible In order for nitrogen to become useable (available for plants and animals), it goes through a cycle which changes it from: N2 (gaseous nitrogen) to NH3 (urea or ammonia) To NO2- (nitrites) which are still relatively inaccessible

And finally to NO3- (nitrate) which is more accessible to plants because it only has single bonds between the nitrogen and oxygen molecules, not double or triple as in the case of nitrite and N2 gas)

Bacteria Bacteria play an important role in the nitrogen cycle, they are able to: Convert N2 into NH3 Convert NH3 into NO2- Convert NH3 and NO2- into NO3-

Bacteria can also fix nitrogen from N2 into the soil Bacteria can also fix nitrogen from N2 into the soil. The nitrogen fixing bacteria are found in lumps on the roots called root nodules. The bacteria and the plant have a symbiotic relationship: the bacteria benefits by having food and shelter from the plant and the plant benefits by having nitrates produced by the bacteria. Roots of a legume plant (peas, beans and clover).

Denitrifying Bacteria Other bacteria called denitrifying bacteria also remove the nitrates and nitrites from the soil and return the nitrogen back to the atmosphere.

decomposition by bacteria & fungi Nitrogen in the air nitrogen fixing plant eg pea, clover animal protein plant made protein dead plants & animals urine & faeces denitrifying bacteria root nodules (containing nitrogen fixing bacteria) decomposition by bacteria & fungi nitrates absorbed nitrates ammonia bacteria nitrites bacteria (nitrifying bacteria)

Biocycles The Phosphorus Cycle

Why Phosphorus? Phosphorus is important in the molecule ATP (Adenosine TriPhosphate), an important energy carrying molecule that acts like a rechargeable battery during cell activities such as photosynthesis and respiration.

The cycle Phosphates/phosphorus is a macronutrient, which means it is needed in large quantities, however it is in limited availability in most habitats, so it’s return to the cycle is very important. Essentially plants are responsible (with the assistance of fungi) for making soil phosphorus available for animals. Animal excretion and death returns the phosphorus to the soil so the cycle can continue. Weathering of phosphorus rich rocks is a further source of phosphorus.

The cycle

Biocycles The Carbon Cycle

Again, carbon is an essential element for life, organic molecules such as carbohydrates are built on a carbon chain backbone. The majority of carbon in the atmosphere is in the form of carbon dioxide (CO2) and is not accessible to animals.