Transcript BIOGEOCHEMICAL CYCLES

BIOGEOCHEMICAL CYCLES
• The flow of energy in the
biosphere is in one
direction only: from the
sun, through living
organisms, into the
environment, and out into
space.
• Matter cycles constantly
from organism to organism
as well as to and from the
environment, which acts as
a reservoir.
• The cyclic pathways taken by various
elements in passing through living
organisms (biotic) and the earth, its
atmosphere and its bodies of water
(abiotic) are generally called
biogeochemical cycles.
• The NITROGEN CYCLE is one of the
most important.
• Proteins and nucleic acids are essential to life. In order
to make them, living things must obtain nitrogen in a
useable form.
• Nitrogen in the air is diatomic (“2-atom”) molecules N2,
and no animal or plant can separate them to use them.
• To be useful the nitrogen must be “fixed”=be attached to
atoms of some other elements to form a compound.
Nitrogen fixation…..
Can occur by:
• Passage of UV light and lightning through the
air = NO3- (nitrate ions) formed
• Volcanoes, combustion of fossil fuels (coal, oil,
natural gas) and forest fires = nitrate and NH3
(ammonia)
• Rain brings the fixed nitrogen to the soil as
NH4- (ammonium ion)
• The bulk of this is carried out by nitrogenfixing bacteria in soil and by cyanophytes
(blue-green bacteria).
• The most efficient nitrogen fixers are
bacteria found in nodules on the roots of
certain plants, notably the legumes (alfalfa,
beans, peas, lentils, clover).
• Fertilizers also add nitrogen to the soil
• Animals must consume Nitrogen in the
form of already formed amino acids in
their food.
• Excretions of animals and the dead
bodies of all organisms are broken
down in the soil by decomposers in the
process of ammonification , which
produces ammonia.
• Nitrifying bacteria convert the ammonia to
NO2- (nitrite ion), then another group of
nitrifying bacteria convert the nitrite ion to
NO3- (nitrate ion). This is know as
nitrification.
• Nitrate is readily taken up by
roots of plants and utilized.
• Denitrifying bacteria convert nitrate to N2O
(nitrous oxide) or N2 (nitrogen gas), which is
then lost to the atmosphere.
• Nitrogen is lost from soil by erosion and carried
into streams, rivers, and ultimately the ocean.
• It then cycles through aquatic organisms.
• Eventually, some nitrogen is lost to sediments at
the bottoms of oceans or lakes.
http://www.biology.ualberta.ca/facilities/multimedia/uploads/intro-biology/ncycle.swf
Assignment:
1)Diagram and label one of the
Biogeochemical Cycles. (pg371-374)
2)Provide a caption under it explaining what
is occurring.
3)Answer Section 4 Review (questions 1-8)
on pg. 374.(due by end of class on Wed..
9/8)
Finish your Energy Pyramid model first