Transcript Carbon Cycle

Chapter 5.2
The Cycling of Materials
Environmental Science
Spring 2011
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Describe short term and long term
process of carbon cycle
Identify one way that humans are
affecting the carbon cycle
List the three stages of the nitrogen cycle
Describe the role that nitrogen-fixing
bacteria play in the nitrogen cycle
Explain how the excess use of fertilizer
can affect the nitrogen and phosphorous
cycle
Objectives
Carbon is an essential component of
proteins, fats, and carbohydrates, which
make up all organisms
 Carbon Cycle: process by which carbon
is cycled between the atmosphere, land,
water, and organisms
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The Carbon Cycle
Carbon enters short term cycle in an
ecosystem when producers (plants)
convert carbon dioxide in the atmosphere
into carbohydrates
 Consumers eat producers- consumers
obtain carbon from carbohydrates
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The Carbon Cycle- short term cycle
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As consumers break down food during
cellular respiration, some of carbon
released back into atmosphere as carbon
dioxide
◦ Organisms that make their own food through
photosynthesis, release carbon dioxide during
cellular respiration too
The Carbon Cycle- short term cycle
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In the long term cycle:
◦ Carbon converted to carbonates- make up hard
parts of bones and shells
◦ Carbonate deposits produce formations of
limestone
◦ Limestone = carbon sink
The Carbon Cycle- long term cycle
Some carbohydrates converted to fats,
oils, and storage molecules
 Carbon in these may be released into soil
or air after an organism dies
 Can form deposits of coal, oil, natural as
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◦ Fossil fuels
The Carbon Cycle- long term cycle
In the year 2000, vehicles were the
source of one-third of all carbon dioxide
emitted in the US
 Release carbon when burn fossil fuels
 Result in steady increase of carbon
dioxide in the atmosphere
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◦ Contribute to global warming: overall
increase in Earth’s temperature
Humans and Carbon Cycle
Nitrogen cycle: process in which
nitrogen is cycled between atmosphere,
bacteria, and other organisms
 All organisms use nitrogen to build
proteins, which are used to build new cells
 Nitrogen makes up 78% of the gases in
the atmosphere
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◦ Most organisms cannot use atmospheric
nitrogen!!
Nitrogen Cycle
Nitrogen must be altered or fixed before
organisms can use it
 Nitrogen-fixing bacteria: only
organisms that can fix atmospheric
nitrogen into chemical compounds
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◦ Other organisms depend on these bacteria to
supply nitrogen
Nitrogen Cycle
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Nitrogen fixing bacteria live in nodules on
the roots of plants called legumes
◦ Beans, peas, clovers
◦ Some live in soil
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Bacteria use sugars provided by the
legumes to produce nitrogen containing
compounds such as nitrates
◦ Excess nitrogen is released into the soil
Nitrogen Cycle
Plants that do not have these bacteria get
their nitrogen from the soil
 Animals get nitrogen from eating plants or
other animals
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Nitrogen Cycle
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Decomposers
◦ Break down wastes such as urine, dung,
leaves, and other decaying plants and animals
and return the nitrogen that these wastes
contain to the soil
◦ After returned to soil bacteria transform a
small amount of the nitrogen into nitrogen gas,
which returns to atmosphere
Nitrogen Cycle- decomposers
Phosphorous Cycle: movement of
phosphorous from the environment to
organisms and then back to the
environment
 Phosphorous is part of many molecules
that make up cells
 Cycle rarely includes atmosphere because
phosphorous rarely occurs as a gas
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◦ Slow cycle
Phosphorous Cycle
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Phosphorous entering soil and water:
◦ Rocks eroding: small amounts of phosphorous
dissolve as phosphate in soil and water
◦ Added to soil and water when excess
phosphorous is excreted in waste from
organisms and when organisms die and
decompose
Phosphorous Cycle
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Phosphorous entering soil and water:
◦ Some phosphorous also washes off the land
and ends up in ocean
 Phosphate salts are not soluble in water, so they
sink to bottom of ocean, accumulate as sediment
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Plants absorb phosphates in the soil
through their roots
◦ Animals absorb phosphates from plants
Phosphorous Cycle
People apply fertilizers
 Fertilizers contain nitrogen and
phosphorous
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Fertilizer and Nitrogen and
Phosphorous Cycles
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If excess used, fertilizer can enter
terrestrial and aquatic ecosystems
◦ Causes overabundant growth of algae: algae
bloom
 Can deplete ecosystem of important nutrients
such as oxygen
Fertilizer and Nitrogen and
Phosphorous Cycles
Burn fuel  nitric oxide released into
atmosphere
 Nitric oxide can combine with oxygen and
water vapor to form nitric acid
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◦ Contributes to acid precipitation
Acid Precipitation
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Create a book outlining each of the
cycles:
◦ Carbon cycle- include atmospheric CO2,
Photosythnesis, Respiration, Combustion,
Natural gases and Coals, Decomposition,
Limestone
◦ Nitrogen cycle- atmospheric nitrogen, runoff,
nitrogen-fixing bacteria, bacteria in soil and
water, lightning
◦ Phosphorous cycle- rain, phosphate mining,
fertilizer, runoff, phosphate in water,
decomposition, phosphate in soil, phosphate in
rocks
Assignment