CS_Ch9_Environment 2/28/05 2:21 PM Page 602

A Vote for Ecology

Bio Words is called , and is carried out by that do not denitrification: the require oxygen. Denitrification ensures the balance between soil conversion of and nitrites to nitrates, nitrites, and atmospheric nitrogen, and completes the gas, which is released . into the atmosphere phosphorous cycle: the Older lawns often have many denitrifying bacteria.The fact that cycling of environmental denitrifying bacteria grow best where there is no oxygen may help phosphorous through a long-term cycle involving explain why people often aerate their lawns in early spring. By rocks on the Earth’s crust, exposing the denitrifying bacteria to oxygen, the breakdown of and through a shorter cycle involving living nitrates to nitrogen gas is reduced. Nitrates will then remain in the organisms soil, and can be used by the grass to make proteins. THE PHOSPHOROUS CYCLE The phosphorous cycle is different from the water, carbon, and nitrogen cycles because phosphorous is not found in the atmosphere. Phosphorous is a THE necessary element PHOSPHOROUS in DNA, in many CYCLE molecules found in living cells, and in the bones of vertebrate animals. uplifting Phosphorous tends of rock to cycle in two weathering ways: a long-term of rock cycle involving the rocks of the Earth’s p ts als crust, and a short- in rock term cycle involving living organisms. phosphates phosphates In the long cycle living things divert phosphates from detrivores rock i the normal rock cycle. Phosphorous is found in bedrock in the form of

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