biogeochemical cycles. the flow of energy in the biosphere is in one direction only: from the sun,...
TRANSCRIPT
• 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 nitrogen-fixing 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
