Biogeochemical Cycles

Decomposers

Cycled Compounds

CO₂

H₂O

NO₃

Producers

Primary

Consumers

Secondary Consumers

Energy Flowing Through Ecosystems

BIOGEOCHEMICAL

Bio = organisms

Geo = in the lithosphere

Chemical = molecules

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Biogeochemical cycles transport molecules through the biotic and abiotic parts of the Earth.

The Nitrogen Cycle

The Carbon Cycle

1. Carbon’s Location

a. The concentration of carbon in living matter (18%) is almost 100 times greater than its concentration in the earth (0.19%).

b. Living things extract carbon from their nonliving environment.

c. For life to continue, this carbon must be recycled.

2. Carbon exists in the nonliving environment as:

a. Carbon dioxide (CO₂) in the atmosphere and dissolved in

water forming HCO₃).

b. Carbonate rocks (limestone and coral = CaCO₃).

c. Deposits of coal, petroleum, and natural gas derived from

once-living things.

d. Dead organic matter (humus in the soil).

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3. Carbon enters the biotic world through the action of producers that photosynthesize.

a. Photosynthesis means “putting together with light”.

b. photosynthesis is how producers trap carbon.

4. Carbon returns to the atmosphere and water by

a. respiration (as CO₂)

b. burning

c. decay (producing CO₂ if oxygen is present, methane (CH₄) if it is not.

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