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Page history last edited by Saavan_Chintalacheruvu@bths.mcvsd.org 8 years, 10 months ago


Biogeochemical Cycles

I. What are Cycles?

A. Cycles are a process in which there is no exact starting point.

B. The process repeats in a perpetual manner with each step causing an effect spurring another.

II. The Water Cycle

A. Evaporation

1. Water evaporates into the atmosphere.

Liquid --> water vapor (gas)

B. Condensation

1. Water condenses into droplets in the clouds.

Water vapor (gas) -> Liquid

C. Precipitation

1. As the water droplets in clouds enlarge, water falls to earth in the form of rain, snow, or hail.

D. Infiltration

1. to pass into or through a substance by filtering or permeating

III. The Nitrogen Cycle

A. Chemical Forms of Nitrogen:

Nitrogen is "changed" into its many forms through chemical reactions with living and nonliving things.

1. N2 - nitrogen gas

2. NO3 - nitrate

3. NH3 - ammonia

B. Nitrogen fixation

1. Caused by bacteria, lightning, and industry - the conversion of nitrogen in air into ammonia; N2 to NH3

C. Nitrification

1. the conversion of ammonia to nitrate; NH3 to NO3

D. Assimilation

1. plants use the NH3 or NO3 to make nitrogen containing compounds (proteins, nucleic acids); NH3/NO3 to N containing compounds

E. Denitrification

1. bacteria convert nitrate to nitrogen gas; NO3 to N2

IV. The Carbon Cycle

A. The Long Term Cycle

1. Organic matter is buried underground and is converted into:

a. peat, coal , oil, & gas

B. The Short Term Cycle

1. The burning of fossil fuel, such as in factories and cars, returns carbon back to the atmosphere.

V. Why?

A. The law of Conservation of Mass states that matter can NOT be created of destroyed.

Therefore, it is cycled in different forms. For example, the amount of water in the world will always be constant.

B. Transformed from one form to another because it needs to be in a usable form for living things.

The nitrogen cycle is an example of this. Nitrogen in air can not be harnessed by animals. Therefore, through a process including other living organisms, it is converted to usable forms for humans.



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