Cycles of Matter
Cycles of Matter: Why?
• Because we have a fixed amount of STUFF
(matter) on this planet, and no new stuff is
being added from the universe
• It must be cycled around and around.
Nitrogen Cycle – Why do we need
nitrogen?
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In proteins (the building blocks of cells)
No nitrogen?
No proteins
No cells
No life
Nitrogen Cycle
• ~79% of air is made up of nitrogen
• We can’t use this form
• Must be “fixed” into solid form
Nitrogen Cycle
• The process of converting nitrogen from the
gaseous form, N2, into a solid form that’s
usable for our bodies is called NITROGEN
FIXATION
Nitrogen Fixation
• It takes a lot of energy to change nitrogen
from its very stable form in the air, N2 to a
form our bodies can use.
• There are 3 ways nitrogen can be fixed:
1. Lightning
2. Nitrogen fixing bacteria
3. factories
Nitrogen Fixation - lightning
1. The high energy from lightning breaks some
nitrogen molecules apart, allowing them to
bond with oxygen in the air.
2. Then rain carries these new compounds
down to the soil.
Nitrogen fixation - bacteria
• Nitrogen diffuses into soil,
• Special species of bacteria in the ground fix
the nitrogen into ammonia and other nitrogen
compounds
• Two types of nitrogen-fixing bacteria
1. free living bacteria
2. Bacteria that live in nodules of certain plants’
roots in a ______________ relationship
• Symbiotic mutualism
Nitrogen fixation - bacteria
• Plants that contain nitrogen-fixing bacteria in
their root nodules:
• Alfalfa, legumes, clover & soy
• Farmers sometimes rotate these crops in just to
add more nitrogen to their soil
Nitrogen Fixation - factories
• Humans have learned how to take gaseous
nitrogen, N2, and fix it into compounds to
make fertilizer
• This takes huge amounts of energy
Nitrogen Cycle - Usage
• Once the nitrogen is fixed in one of the three
ways, it can be used by plants
Nitrogen Cycle - Usage
• Finally, heterotrophs get
the nitrogen by eating the
plants or other animals
that ate the plants.
Nitrogen Cycle – Back to Air
• When organisms die, decomposers get the last
of their stored energy, and return their
elements back to the soil.
• Some decomposing archaea break down the
nitrogen compounds and release them back to
their gaseous form, N2.
• This process of breaking down nitrogen
compounds and releasing them back as air is
called denitrification.
• Nitrogen cycle web site
• nitrogen cycle animation
Carbon (C) and Oxygen (O) cycles
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Plants do photosynthesis
What do plants use for this?
Water (H2O) and Carbon Dioxide (CO2)
What do plants produce using
photosynthesis?
• Glucose, a sugar (C6H12O6) and oxygen (O2), a
waste product for plants
Carbon (C) and Oxygen (O) cycles
• All living things do cellular respiration to get…
• ENERGY
• What do plants and animals use for cellular
respiration?
• Oxygen (O2) and glucose (C6H12O6) – exactly
the products of photosynthesis!
Carbon (C) and Oxygen (O) cycles
• And cellular respiration produces what
photosynthesis needs: carbon dioxide and
water.
• So the carbon and oxygen cycle around
through cellular respiration and
photosynthesis
Carbon (C) and Oxygen (O) cycles
• When organisms die, their bodies still contain the
substances they had when they were alive.
• These get cycled back into the ground by …
• decomposers.
• When organisms die, the energy left over in their
bodies is still stored in the carbohydrate
compounds in their tissues.
• Organisms that died long ago and were buried
under layers of sediments have been pressurized
for many years and converted into …
• Fossil fuels
• Fossil fuels come in the form of gasoline, oil, &
coal.
• When we burn these fuels, this releases the
carbon dioxide back into the air, just like
breathing out does from cellular respiration.
• The process of powering a car with fossil fuels is
the same as powering our bodies with fuel from
plants – both produce carbon dioxide.
• All the energy originally came from…
• the sun .