Biogeochemical Cycles
Chapter 37.15 – 37.20
What you need to know!
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
The water, carbon, nitrogen, and phosphorus
chemical cycles
The various abiotic reservoirs for each cycle
Nutrients Recycle
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Biogeochemical cycles are the interactions
between biotic and abiotic factors that account for
the recycling of nutrients in an ecosystem
All four major cycles share a pattern:
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Nutrients are stored in an
abiotic reservoir
Nutrients move through the
food web
Detritivores decompose
everything back to the
reservoir
The Water Cycle
Water Cycle
1.
2.
3.
4.

Evaporation & transpiration (from plants) accounts
for all the water in the atmosphere.
Water forms clouds (condensation), and then rains
(precipitation) back down to the Earth.
Water runs into streams and rivers (runoff) or is
absorbed into the ground (seepage) to become
ground water.
Water is taken up by the roots of plants or it makes
its way to the oceans, flowing above ground or
below ground.
Abiotic Reservoir = Oceans, Lakes, & atmosphere
The Carbon Cycle
Carbon Cycle
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Photosynthesis, cellular respiration, and
decomposition take up and release Carbon and
Oxygen.
Volcanic eruptions and erosion release Carbon
Dioxide into the atmosphere and oceans
Burial and decomposition of dead organisms store
Carbon underground (coal & oil).
Human activities, such as cutting and burning
forests, and burning fossil fuels, release Carbon
Dioxide into the atmosphere.


Climate change (global warming)
Abiotic Reservoir = atmosphere & fossil fuels
The Nitrogen Cycle
Nitrogen Cycle

Nitrogen Fixation changes the nitrogen in the
air into nitrogen that plants can use in the soil
(nitrate ions & ammonium ions).
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Lightning, bacteria, fertilizer
Once Nitrogen has been fixed in the soil it is
then taken up by the roots of plants
(producers).
Abiotic Reservoir = atmosphere
The Phosphorus Cycle
Phosphorus Cycle

It is not abundant in the atmosphere, so it
follows a simple cycle.
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
soil  producer  herbivore  carnivore 
decomposer  back to soil
Abiotic reservoir = rocks
Human Disturbance
Human alteration of habitats can impact
multiple ecosystems
Example:
 When forests are cut down there are fewer
plants to absorb essential nutrients in the soil
 Water washes the nutrients away to other
ecosystems

These other
ecosystems are also
altered
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