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Botkin & Keller

Environmental Science 5e

Chapter 5

The Biogeochemical Cycles

Botkin & Keller


How Chemicals Cycle

• Biogeochemical Cycle

– The complete path a chemical takes through

the four major components – or reservoirs –

of Earth’s systems

1. Atmosphere

2. Hydrosphere

3. Lithosphere

4. Biosphere

Botkin & Keller


Chemical Reactions

• Chemical reaction:

– The process in which new chemicals are

formed from elements and compounds

through chemical change

Botkin & Keller


© 2008 John Wiley and Sons Publishers

Botkin & Keller


Biogeochemical Cycles and Life• Macronutrients

– Elements required in large amounts by all life

– Include the “big six” elements that form the fundamental building blocks of life:

Carbon

oxygen

hydrogen

phosphorus

nitrogen

sulfur

• Micronutrients– Elements required either in

• small amounts by all life or

• moderate amounts by some forms of life and not all by others

Limiting Factor

• When chemical elements are not available

at the right times, in the right amounts, and

in the right concentrations relative to each

other

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Botkin & Keller


The Geologic Cycle

• The Geologic Cycle:

– The processes responsible for formation and

change of Earth materials

– Best described as a group of cycles:

• Tectonic

• Hydrologic

• Rock

• Biochemical

Botkin & Keller



Botkin & Keller


Tectonic Cycle

• Tectonic cycle:

– Involves creation and destruction of the solid

outer layer of Earth, the lithosphere

• Plate tectonics:

– The slow movement of these large segments

of Earth’s outermost rock shell

– Boundaries between plates are geologically

active areas

Botkin & Keller



Botkin & Keller


Tectonic Cycle: Plate Boundaries

• Divergent plate boundary:– Occurs at a spreading ocean ridge, where plates are

moving away from one another

– New lithosphere is produced (seafloor spreading)

• Convergent plate boundary– Occurs when plates collide

• Produces linear coastal mountain ranges or continental mountain ranges

• Transform fault boundary– Occurs where one plate slides past another

• San Andreas Fault in California

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The Hydrologic Cycle

• The Hydrologic Cycle:

– The transfer of water from the oceans to the

atmosphere to the land and back to the

oceans. Includes:

• Evaporation of water from the oceans

• Precipitation on land

• Evaporation from land

• Runoff from streams, rivers, and sub-surface

groundwater

Botkin & Keller



Botkin & Keller


The Rock Cycle

• The rock cycle:

– Numerous processes that produce rocks and soils

– Depends on other cycles:• tectonic cycle for energy

• Hydrologic cycle for water

– Rock is classified as • Igneous

• Sedimentary

• Metamorphic

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Botkin & Keller


The Carbon Cycle

• Carbon is the element that anchors all

organic substances

• The carbon cycle:

– Carbon combines with and is chemically and

biologically linked with the cycles of oxygen

and hydrogen that form the major compounds

of life

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Botkin & Keller


The Carbon Cycle:Unanswered Issues

• The Missing Carbon Sink

– Substantial amounts of carbon dioxide

released into the atmosphere but apparently

not reabsorbed and thus remaining

unaccounted for

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Botkin & Keller


The Carbon-Silicate Cycle

• The carbon-silicate cycle:

– A complex biogeochemical cycle over time scales as

long as one-half billion years.

– Includes major geological processes, such as:

• Weathering

• Transport by ground and surface waters

• Erosion

• Deposition of crustal rocks

– Believed to provide important negative feedback

mechanisms that control the temperature of the

atmosphere.

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Botkin & Keller


The Nitrogen Cycle

• The nitrogen cycle:– Cycle responsible for moving important nitrogen

components through the biosphere and other Earth systems

– Extremely important because nitrogen is required by all living things

• Nitrogen fixation:– The process of converting inorganic, molecular

nitrogen in the atmosphere to ammonia or nitrate

• Denitrification:– The process of releasing fixed nitrogen back to

molecular nitrogen

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Botkin & Keller


The Phosphorus Cycle

• The phosphorus cycle:

– Involves the movement of phosphorus

throughout the biosphere and lithosphere

– Important because phosphorus is an essential

element for life and often is a limiting nutrient

for plant growth.

Botkin & Keller



chapter 5 - folsom cordova unified school district · pdf filebotkin & keller...

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