Withgott Environmental Science Chapter 3, Lesson 4 Pages 83-90

Nutrients cycle through the endlessly through the environment, through living organisms, and back into the environment.

 Explains why the amount of matter in the environment stays the same as it flows through nutrient (biogeochemical) cycles  Nutrients are substances that living things require for life processes  Nutrient cycles = biogeochemical cycles

1. Reservoir – atmosphere (as CO 2 ), sediments (fossil fuels-oil, coal), durable organic materials (for example: cellulose), oceans (absorb C from atmosphere, runoff and undersea volcanoes) 2. Assimilation – Primary producers (plants, algae) use CO 2 in photosynthesis; animals consume plants. 3. Release – plants and animals release CO 2 through respiration and decomposition; CO 2 is released as wood and fossil fuels are burned.

 P is needed to make cell membranes, nucleic acids (DNA, RNA) and energy in the form of ATP  There are enormous amounts of P in rocks, soil, sediments, and the ocean  P is released when rocks are worn by water or wind (erosion)  Plants and algae growth jumps dramatically when P is added to their environments

1. Reservoir – erosion transfers P to water and soil; sediments/rocks that accumulate on ocean floors return to the surface due to uplifting by geological processes 2. Assimilation – plants absorb inorganic PO 4 3- (phosphate) from soil; animals obtain P when they eat plants/animals 3. Release – plants and animals release P when they decompose; animals excrete phosphorus in their waste products

 Phosphorus is mined as fertilizer  Wastewater is frequently rich in Phosphorus (detergents)  Adding phosphorus to bodies of water leads to eutrophication: overgrowth of producers, usually algae  Eutrophication leads to low levels of oxygen in a body of water  This occurred in the Gulf of Mexico

Nitrogen is required to make amino acids (proteins) and nucleic acids The Nitrogen Cycle relies on bacteria that make nitrogen useful to organisms and bacteria that return t to the atmosphere Nitrogen makes up 78% of our atmosphere by mass and is the 6 th most abundant element

 To be used by living things, nitrogen must be chemically changed by bacteria or human technology  Nitrogen Fixation: nitrogen gas is converted to ammonia by a lightning strike or nitrogen fixing bacteria in the soil or in plants (clover, soybeans, legumes)  Reservoir – atmosphere (as N 2 ); soil (as NH 4 + or ammonium), NH 3 (ammonia), N0 2 - (nitrite), N0 3 - (nitrate)

2. Assimilation – plants absorb nitrogen as either NH 4 + or N0 3 -, animals obtain N by eating plants/other animals. The stages in N assimilation are as follows: Nitrogen Fixation: N 2 to NH 4 + by N- fixing bacteria, N 2 to N0 3 - by lightning/UV radiation. Nitrification: NH 4 + to N0 2 - and N0 2 - to N0 3 - by various nitrifying bacteria.

3. Release – Denitrifying bacteria convert N0 3 - back to N 2 (denitrification); bacteria convert organic compounds back to NH 4 + (ammonification); animals excrete NH 4 + (or NH 3 ) urea, or uric acid.

1. Reservoir – oceans, air (as water vapor), groundwater, lakes and glaciers; evaporation, wind and precipitation (rain) move water from oceans to land 2. Assimilation – plants absorb water from the ground, animals drink water or eat other organisms which are composed mostly of water 3. Release – plants transpire, animals breathe and expel liquid wastes

Biogeochemical cycles of other minerals, such as calcium and magnesium, are similar to the phosphorus cycle.