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Ecology Part 6Carbon & Nitrogen Cycles
R. Martinez, 2012
What is Carbon?
• An element• The basis of life
on earth• Also found in
rocks, oceans, atmosphere
Carbon is recycled
• The same carbon atoms are used repeatedly on earth.
• They cycle between the earth and the atmosphere.
bioticabiotic
How does carbon move?
• Photosynthesis - CO2 is taken from the air and trapped into food (glucose)
• Cellular Respiration - CO2 is returned to the atmosphere when food (glucose) is broken down
Plants absorb CO2 and
make sugar while consumers eat sugar
and release CO2. It
makes a cycle – the carbon cycle!
• Plants absorb CO2 (photosynthesis) and release
CO2 (respiration).
• Plants use sugar to make their cell walls so they absorb far more carbon dioxide than they produce.
• Most animals cannot digest cellulose which is what plants cell walls are made of, so when plants are eaten or die, the carbon that was absorbed by the plant is trapped. This is where decomposers come in...
The Role of the Decomposer
• Decomposers are usually bacteria and fungi, and they can use the energy trapped in dead plants and animals.
• In the process they release CO2 so living plants have what they need to make more sugar!
The Role of the Decomposer
How does deforestation and the destruction of
other photosynthetic
organisms affect the carbon cycle?
What happens when we disrupt a cycle?
Without plants, carbon dioxide would build up in the atmosphere and the amount of oxygen available to animals would be reduced.
Any disruption to a cycle leads to
the ENTIRE cycle being affected.
What is Nitrogen?
• 79% of the atmosphere is nitrogen gas but it is in a form most living things cannot use.
N2
freenitrogen
Why do we need Nitrogen?
Our DNA, RNA, and PROTEINS
all REQUIRE NITROGEN!
How do we get Nitrogen?
• Nitrogen fixation is N2 NH3 (ammonia)
• Nitrogen-fixing bacteria convert nitrogen into ammonia/nitrates.
• Plants absorb nitrates.• Animals eat plants.
N2
in airnitrogen-fixing
bacteria
NITRATES
Nitrogen Fixation
normal conditions.
Nitrogen fixation can also be caused by lightning!
How does Nitrogen return to the atmosphere?
• Denitrifying bacteria convert the nitrates back into nitrogen.
When plants and animals die, the nitrogen contained in these organisms is digested by decomposers and released into the soil as ammonia. Without these decomposers, the nitrogen would remain trapped in the dead animals. These decomposers recycle the nitrogen and are a key component of the cycle.
The Role of the Decomposer
The Nitrogen Cycle
Fish death due to depleted oxygen
While too little nitrogen can be a problem, too much nitrogen can
also cause problems. When fertilizers containing nitrogen get
into the water supply, they can make it too easy for
microorganisms like bacteria and plankton to grow. These organisms deplete the water of oxygen. With
this oxygen gone, aquatic and marine life suffer and often die
because they do not have the O2 they need.
What happens when we disrupt a cycle?
Any disruption to a cycle leads to
the ENTIRE cycle being affected.
