Cycling of Matter
Oxygen
Carbon
Nitrogen
Change & Recovery in Ecosystems
What happens to the
materials that make up
a truck when it begins
to rust?
What happens to the
tree after it dies?
Cycling of Matter in Ecosystems Organic substances
Contain atoms of Carbon and Hydrogen
Are broken down into simpler forms in living things
Ex. Sugar, carbohydrates, proteins, amino acids
Inorganic substances Do not contain combination of
carbon and hydrogen Ex. Water (H2O), ammonia
(NH3), Carbon dioxide (CO2)
Biological Processes Involved in Nutrient
Cycling
1. Photosynthesis
Plants convert CO2 and H2O into O2 and sugar
6CO2 + 6H2O + energy → C6H12O6 + 6O2
2. Respiration
Animals AND plants use O2 and sugar,
converting it to CO2 and H2O
C6H12O6 + 6O2 → 6CO2 + 6H2O + energy
More Processes 3. Decomposition
• Remains of dead organisms are broken down by bacteria and fungi
• All molecules are released into soil
4. Excretion
• Waste material from animals is broken down and returned to the soil
5. Assimilation
• Conversion of molecules into a useable form by bacteria
• Nitrification, denitrification
Cycling of Organic Matter The atoms and molecules
available to make up organisms on earth is limited
All the atoms MUST be recycled in order for new organisms to form.
It is very likely that at least one of the carbon atoms in your body was also in a 70 million year old dinosaur
Recycling of Matter by Micro-organisms
The Matter Cycle
Soil
Grass
Cow Person
Decomposers
1. Dead plants and animals are broken down
by decomposers – their atoms / molecules
are released into the system to be re-used
2. Atoms, molecules accumulate in the soil
3. Nutrients are taken up by grasses
4. Cows eat the grass – nutrients and atoms
are passed on to the cow
5. Person eats cow – nutrients and atoms are
passed on to person
6. Each of these things can die, the atoms are
broken down by decomposers and
recycled for the next living things
The Oxygen Cycle
Respiration:
C6H12O6 + O2 CO2 + H2O + energy
Photosynthesis:
CO2 + H2O + light C6H12O6 + O2
What do you notice about these two chemical
reactions?
The Oxygen Cycle
Oxygen
(in atmosphere)
RESPIRATION by plants, animals and decomposers
Carbon Dioxide
(in atmosphere)
PHOTOSYNTHESIS
by green plants Combustion
(burning stuff)
The Carbon Cycle CO2 in the atmosphere
volcanic
eruption
CO2
dissolved in
water
Ocean
sediment
combustion
Fossil fuels Conversion to fossil fuels
Decomposition
Glucose
Photosynthesis - carbon
is stored in the biomass
Aerobic
respiration
Weathering
The Carbon Cycle
Two groups of carbon sources in the
carbon cycle 1. Biotic - Aerobic respiration (in the presence of
O2), and decomposition
The organic reservoirs (storage areas) for
carbon are the bodies of living things
2. Abiotic - Combustion and geological activity
The inorganic reservoirs for carbon are
the atmosphere, the oceans, and the
Earth’s crust
The Nitrogen Cycle
The movement of nitrogen through ecosystems, soil, and
the atmosphere is called the nitrogen cycle.
Nitrogen is a component of many organic molecules.
forms an essential part of amino acids (the building
blocks of proteins) and DNA.
is essential for all living cells.
in gas form (N2) makes up about 78% of atmosphere.
The Nitrogen Cycle
Most organisms cannot use nitrogen in the gaseous
form found in the air we breathe, so it must be in
“fixed” forms that plants can absorb.
“Fixed” nitrogen compounds that plants CAN use:
nitrate ions (NO3−)
ammonia (NH3)
urea (NH2)2CO
The Nitrogen Cycle ~ 4 Processes Process #1 ~ NITROGEN FIXATION
To “fix” the nitrogen in the air, it must have its bonds broken so
it can combine with other atoms to enter the food chain. This
takes substantial amounts of ENERGY.
Three ways N2 bonds can be broken:
Atmospheric fixation - lightening breaks
nitrogen molecules and enables their atoms to
combine with oxygen in the air forming
nitrogen oxides. These dissolve in rain,
forming nitrates that are carried to the earth.
only a small amount is fixed this way ~ about 10%
Nitrogen Fixation (cont.)
Biological fixation – Bacteria are the only
organisms able to take N2 and combine it with
hydrogen to make ammonia.
Most are free-living in soil.
Some have developed an association with
certain plants. In return for sugars from the
plant, these bacteria fix nitrogen which can
be used by the plant for growth.
bacteria fix 60% of nitrogen gas
Nitrogen Fixation (cont.)
Industrial fixation – In the manufacturing
process, N2 is converted together with
hydrogen gas (H2) into ammonia (NH3).
Ammonia can be used directly as fertilizer, but
most of it is further processed to urea and
ammonium nitrate (NH4NO3).
Today, about 30% of the total fixed nitrogen is manufactured in ammonia chemical plants.
The Nitrogen Cycle ~ 4 Processes
a process by which nitrogen-fixing bacteria oxidize
ammonia first into nitrites (NO2 –) and then into nitrates
(NO3–).
Two different bacteria are involved. One transforms
ammonia to nitrites, the other transforms the nitrites to
nitrates.
plants can easily absorb nitrates and use them to form
proteins (to then be used in food chains).
Process #2 ~ NITRIFICATION
The Nitrogen Cycle ~ 4 Processes
decomposers break down the molecules in excretions and
dead organisms into ammonia.
most of the ammonia produced by decay is converted into
nitrates by nitrifying bacteria (nitrification process).
Process #3 ~ DECAY
The Nitrogen Cycle ~ 4 Processes
The only process that puts nitrogen back into the
atmosphere by reducing nitrates into nitrogen gas (N2).
Bacteria that live deep in the soil and in aquatic sediments
where there is no oxygen use the oxygen atom in the
nitrate (NO3−) for their respiration, thus closing the cycle.
Process #4 ~ DENITRIFICATION
Schematic representation
of the flow of nitrogen
through the environment.
The importance of
bacteria in the cycle is
immediately recognized
as being a key element in
the cycle, providing
different forms of
nitrogen compounds
taken on by higher
organisms.
Nitrogen Cycle ~ review
Nitrogen Cycle ~ review
The Nitrogen Cycle
The Nitrogen Cycle
Essential to living things for the production of amino acids used to synthesize proteins, and nucleic acids which are used to carry the hereditary or genetic code
Plants and animals are unable to use any of the N2 that is in the atmosphere
The nitrogen cycle can occur in both terrestrial and aquatic ecosystems
Nitrogen Cycle Complex cycle can be simplified as follows
For plants to make use of nitrogen it must first be
converted into ammonia or nitrates (NO3-)
two pathways that produce nitrate ions:
fixation by lightning (produces nitrates directly)
fixation by bacteria (producing ammonia) followed by
nitrification by bacteria (converting the ammonia to
nitrates)