VIII. Cycles in the Environment

A. Carbon Cycle

1. Originally thought that the Earth was 95% carbon dioxide

a. Plants and bacteria removed it and replaced with oxygen

b. Today about .04%

2. Living things are the most important to the carbon cycle (made of carbon)a. Photosynthesis1. H2O+ CO2+light C6H12O6+ O2

b. Respiration1. C6H12O6 + O2 H2O + CO2 + energy

3. Most carbon is tied up in living organisms

a. Also in oceans b/c its easily dissolved

b. Rocks also have a lotc. Some as coal, oil, and natural

gas4. Other sources of atmospheric

carbon is through burning of fossil fuels and volcanic eruptions

B. Nitrogen cycle

1. Everything needs N in order to make amino acids so they can make proteins2. Most things cannot use gaseous N3. Only specific types of bacteria are capable of “fixing” it into useful forms

4. Several steps are involved in the process

a. N-fixing bacteria converts N into NH3 (ammonia)1. Legumes have colonies

of these bacteria in nodules on roots

2. Other bacteria make nitrite and nitrate out

of ammoniab. Nitrate is used by plants to

make protein

c. Animals get nitrogen by eating plants

d. Animals and plants die and are consumed by decomposers

1. Ammonia is a by product of decomposition

e. Can remain in the soil or go back into the air to start the

process over