Cycling of Material in an
Ecosystem
• Important nutrients,
and energy is cycled in
ecosystems.
• Water cycle
• Carbon cycle
• Nitrogen cycle
• Phosphorus
What four elements make up over
95% of most organisms?
•
•
•
•
Oxygen
Carbon
Hydrogen
Nitrogen
Water Cycle
Fig 9-3
Water Cycle
• Transpiration – water enters the atmosphere by
evaporating from the leaves of plants
• Precipitation – water enters the atmosphere as
rain fall
• Evaporation – Water changes from liquid to gas
• Condensation – Water changes from gas to liquid
• Runoff- runs along surface and becomes ground
water.
Compass Activity Bi1341
• http://compass.rcschools.net/clologin.aspx
• Log on to Compass and enter the activity code
for lesson.
Carbon Cycle
• CO2 is taken up by plants during
photosynthesis
• CO2 is released by organisms during
respiration and decomposition; fires,
volcanoes
• CO2 is also released by autos and
industries
• carbon, present in all organic molecules,
moves through the food chain as one
organism eats another
Carbon Cycle
Three large reservoirs where carbon is found in the
biosphere.
• Atmosphere as CO2 gas
• Oceans as dissolved CO2
• Underground as coal petroleum, and calcium
carbonate rock
There is much talk in the news about carbon emissions and high CO2 causing global
warming.
Plants take up CO2 during photosynthesis.
Why don’t plants just take up all the extra CO2 and get it out of the atmosphere?
The Carbon Cycle
• How do the roles of autotrophs and heterotrophs
differ in relation to the carbon cycle?
• Producers take in CO2 and consumers release CO2
during respiration.
• What are the human impacts on the cycle?
• Fossil fuels – factories, vehicles, human activity
• Volcanic activity also releases CO2 into
atmosphere
Oxygen Cycle
• Essential for animals during respiration,
released by plants
• Cycles much like the carbon cycle
• What is threatening this cycle?
• Forest deforestation, ocean pollution, etc
Nitrogen Cycle
Nitrogen Cycle
• 78% of the volume of atmosphere
• Most complex cycle
• N2 gas can’t be used ‘as is’ – it must be ‘fixed’ so that organisms
can use it
• Steps to the cycle: b/c of complexity, no certain order
–
–
–
–
–
N Fixation – occurs in plant, by bacteria
Ammonification
Nitrification
Assimilation
Denitrification
• N2 gas is modified by “nitrogen-fixing” bacteria in legumes into
ammonia (NH3) – NITROGEN FIXATION – aids in production of
sugars/starches
• Denitrification is the process by which some soil bacteria
convert nitrates into nitrogen gas.
Nitrogen fixation: Bacteria in root nodules of legumes
An example of mutualism
Fig 3-19
Nitrogen cycle (con’t)
• Plant roots take up the ammonia and
nitrate ions and converts it into amino
acids which are the building blocks of
proteins
• nitrogen, present in proteins, moves
through the food chain as one organism
eats another
The Nitrogen Cycle
• How and in what form(s) does nitrogen enter and leave
the cycle?
• Bacteria through nitrogen fixation.
• Decomposers return nitrogen to the soil as ammonia.
• Bacteria convert nitrates into nitrogen gas through
denitrification.
• Humans add fertilizer which contains nitrogen
• Why is nitrogen important?
• To make amino acids which build
• PROTEINS!!!!
Nitrogen Cycle
Phosphorus Cycle
Phosphorus Cycle
• phosphorus is released as rocks erode and
plants absorb the phosphorus
• Very slow process
• phosphorus passes from one organism to
another in the food chain
• decomposers release phosphorus during
decomposition
• Mined for production of fertilizer. Mined in
Tampa, FL
The Phosphorus Cycle
• How and in what form(s) does phosphorus
enter and leave the cycle?
• From rocks and soil and enters through water
and plants.
• Why is phosphorus essential to living
organisms?
• DNA and RNA
Phosphorus Cycle
Limiting Nutrient
• A nutrient that is in short supply in an
ecosystem and will slow growth.
• If a limiting nutrient is found in large supply it
can cause an algal bloom to occur.
• Too much of the limiting nutrient will cause
excessive and fast growth of organisms.
A bloom of Cyanobacteria
Cyanobacteria
Anabaena
Microcystis
Nutrient cycling and energy flow through an ecosystem
Fig 3-20
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Cycling of Material in an Ecosystem