Download Biogeochemical Cycles

Botkin & Keller
Environmental Science 5e
Chapter 5
The Biogeochemical Cycles
Botkin & Keller
Environmental Science 5e
Botkin & Keller
Environmental Science 5e
• Chemical reaction:
–The process in which new
chemicals are formed from
elements and compounds through
chemical change
–Examples – H2O + CO2
H2CO3
6H2O + 6CO2
C6H12O6 + 6O2
How Chemicals Cycle
•
Biogeochemical Cycle
– The complete path a chemical takes
through the four major components –
or reservoirs – of Earth’s systems
1. Atmosphere (Air)
2. Hydrosphere (Water)
3. Lithosphere (Rocks)
4. Biosphere (Living Things)
Botkin & Keller
Environmental Science 5e
Cycles Generalized
Botkin & Keller
Environmental Science 5e
The “Big Six” Chemicals
• 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
Botkin & Keller
Environmental Science 5e
Micronutrients
Elements required either in
small amounts by all life or
moderate amounts by some
forms of life and not all by
others
Botkin & Keller
Environmental Science 5e
© 2008 John Wiley and Sons Publishers
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
Botkin & Keller
Environmental Science 5e
• 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
Environmental Science 5e
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
Botkin & Keller
Environmental Science 5e
Botkin & Keller
Environmental Science 5e
© 2008 John Wiley and Sons Publishers
Botkin & Keller
Environmental Science 5e
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
Environmental Science 5e
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
Botkin & Keller
Environmental Science 5e
Botkin & Keller
Environmental Science 5e
© 2008 John Wiley and Sons Publishers
The Water 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 subsurface groundwater
Botkin & Keller
Environmental Science 5e
Botkin & Keller
Environmental Science 5e
Botkin & Keller
Environmental Science 5e
Botkin & Keller
Environmental Science 5e
Botkin & Keller
Environmental Science 5e
The Carbon Cycle
• All living things are made of molecules that
contain Carbon
– Organic = living = contains carbon!
• Organic Molecules, Organic Matter…
• Carbon is “the element of life!”
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
Botkin & Keller
Environmental Science 5e
The Carbon Cycle
The Carbon Cycle
• Carbon is found in the atmosphere as CO2.
• Plants take CO2 in from the air, and in the process of
photosynthesis, make carbohydrate sugars that are
stored in the plant
• Animals eat the plants, and also store Carbon in
their bodies
• Animals also breathe out CO2 back to the
atmosphere as part of respiration
• When any living thing dies, decomposers return
some Carbon to the air as CO2, but the rest of the
Carbon gets put into the soil or water
DEAD
- The Carbon compounds in decaying organisms
deep underground or underwater are eventually
turned into coal, oil, or gas
- called “Fossil Fuels”
- This Carbon is re-released to the air as CO2 when
people burn fossil fuels
DEAD
The Carbon Cycle
CO2 in air
Carbohydrates
in plants
Carbon in
animals
Burning Fossil
Fuels
Decomposers
Break down
decaying animals
DEAD
Carbon in soil
Fossil Fuels
Botkin & Keller
Environmental Science 5e
© 2008 John Wiley and Sons Publishers
Botkin & Keller
Environmental Science 5e
© 2008 John Wiley and Sons Publishers
Botkin & Keller
Environmental Science 5e
© 2008 John Wiley and Sons Publishers
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.
Botkin & Keller
Environmental Science 5e
Botkin & Keller
Environmental Science 5e
© 2008 John Wiley and Sons Publishers
Your Ocean on Acid.m4v
Botkin & Keller
Environmental Science 5e
Botkin & Keller
Environmental Science 5e
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
Botkin & Keller
Environmental Science 5e
The Nitrogen Cycle


Nitrogen is needed by all living things to build
proteins
Nitrogen is found in its gas form in the air around us


but Plants and animals can't use nitrogen in its gas form!
NITROGEN FIXATION: process where Nitrogen gas
is converted into a form plants can use

This process is done by certain bacteria that live in the
water, soil, or that grow on the roots of some legume
(bean) plants



Bacteria capture the nitrogen gas from the atmosphere and make it
usable
Plants then absorb the usable Nitrogen from the soil
Animals eat the plants – and Nitrogen is passed along through the
food chain
• Nitrogen is returned to the soil when
– Animals excrete wastes (pee or poop)
– living things die and are broken down by
decomposers
• Nitrogen is returned to the air by denitrifying
bacteria
• DENITRIFICATION: bacteria in the soil re-convert
nitrogen compounds into nitrogen gas
Botkin & Keller
Environmental Science 5e
© 2008 John Wiley and Sons Publishers
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
Environmental Science 5e
Botkin & Keller
Environmental Science 5e
© 2008 John Wiley and Sons Publishers