Cycles

Water, Carbon, Nitrogen Oxygen and Phosphorus

Water (hydrologic) Cycle

Plants absorb water from the soilTranspiration and respiration return

water to the atmospherePrecipitation returns water to the soilNonmetal oxides in the atmosphere

combine with water to form acid rain

The Carbon Cycle

• Carbon is fixed by plants – 6 CO2 + 6 H2O C6H12O6 + 6 O2

• Carbon is given off by consumers– C6H12O6 + 6 O2 6 CO2 + 6 H2O

• Organisms containing carbon form fossil fuels

• Burning fossil fuels releases carbon– 2 C8H18 + 25 O2 16 CO2 + 18

H2O

Carbon Cycle

Arctic Carbon Cycling

The Nitrogen Cycle

Bacteria fix nitrogen from the airConsumers and producers incorporate

nitrogen into their tissuesNitrogen can be fixed industrially from the

airProduction of ammonia

Decay processes return nitrogen to the airNitrogen from fertilizers may contaminate

water sources

Aquarium Nitrogen Cycle

The Oxygen Cycle

• Oxygen is produced by photosynthesis– 6 CO2 + 6 H2O C6H12O6 + 6 O2

– The largest chemical process on earth!

• Oxygen is sequestered by respiration– C6H12O6 + 6 O2 6 CO2 + 6 H2O

6 CO2 + 6 H2O C6H12O6 + 6 O2

C6H12O6 + 6 O2 6 CO2 + 6 H2O

The Phosphorus Cycle• The element phosphorus (P)is released in

the form of ionic phosphate (PO43-)

– Weathering of rock, mining, some detergents and fertilizers

• Phosphate is taken up by plants and fungi• Consumers absorb phosphate from plants • Decomposers return phosphate to soil• Phosphate leaches into water supply– May form new phosphate containing rock