Download is called denitrification, and is carried out by bacteria that do not

CS_Ch9_Environment
2/28/05
2:21 PM
Page 602
A Vote for Ecology
Bio Words
is called denitrification, and is carried out by bacteria that do not
require oxygen. Denitrification ensures the balance between soil
nitrates, nitrites, and atmospheric nitrogen, and completes the
nitrogen cycle.
denitrification: the
conversion of nitrates
and nitrites to nitrogen
gas, which is released
into the atmosphere
phosphorous cycle: the
cycling of environmental
phosphorous through a
long-term cycle involving
rocks on the Earth’s crust,
and through a shorter
cycle involving living
organisms
Older lawns often have many denitrifying bacteria.The fact that
denitrifying bacteria grow best where there is no oxygen may help
explain why people often aerate their lawns in early spring. By
exposing the denitrifying bacteria to oxygen, the breakdown of
nitrates to nitrogen gas is reduced. Nitrates will then remain in the
soil, and can be used by the grass to make proteins.
THE PHOSPHOROUS CYCLE
THE
PHOSPHOROUS
CYCLE
uplifting
of rock
The phosphorous cycle is different from the water, carbon, and
nitrogen cycles because phosphorous is not found in the atmosphere.
Phosphorous is a
necessary element
in DNA, in many
molecules found in
living cells, and in
the bones of
vertebrate animals.
Phosphorous tends
to cycle in two
weathering
ways: a long-term
of rock
cycle involving the
rocks of the Earth’s
ts
als
p
crust, and a shortin rock
term cycle involving
living organisms.
phosphates
rock
phosphates
detrivores
i
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Active Biology
In the long cycle
living things divert
phosphates from
the normal rock
cycle. Phosphorous
is found in bedrock
in the form of