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					              Ecology
 Energy Transfer and nutrient recycling

WALT
How nutrients are recycled through an
ecosystem
The carbon cycle
• Autotrophs in an Ecosystem are
  producers, the products that they make
  form the food that ultimately feed all of the
  organisms in the ecosystem.
• Primary consumers are herbivores and get
  their energy from feeding on the
  autotrophs
• Secondary consumers feed off the primary
  consumers
• Tertiary consumers prey on other meat
  eaters
 Food chains are chains of dependence
 Each distinct level is called a trophic level


Producers   Primary       Secondary       Tertiary
            consumers     consumers       consumers




As one organism eats another there is a
transfer of energy through the trophic levels
Energy transfer occurs in one direction only
• All organisms need a supply of energy to
  carry out the processes of life
• They also need to obtain mineral nutrients
  such as carbon and nitrogen in order to
  make up complex chemicals such as
  proteins.
• Unlike energy mineral nutrients are
  recycled over and over again
• Some people say that in our lives we will
  breathe out 6 carbon atoms that were
  once a part of Napoleon Bonaparte!!!
Producers accumulate mineral
nutrients

These then pass along the food chains

Finally they are released back into the
 abiotic part of the ecosystem by
 decomposers
  Mineral nutrients occur in four basic
  compartments in an ecosystem
• The organic molecules in living and
  dead organisms
• Organic matter held in the soil
• Fossil fuels and sedimentary rocks
• In the atmosphere
• Dissolved CO2 and Calcium
  Carbonate in the sea
         The Carbon Cycle
• Carbon circulates between the abiotic and
  biotic parts of the ecosystem
            Carbon Cycle
• Fragments of decaying material is called
  detritus
• Small animals known as detritivores feed
  on the detritus and so contribute to the
  decomposition process
• Detritivores include earthworms, woodlice
  and slugs
• Decomposers then complete the
  decomposition – bacteria and fungi
                            photosynthesis

Carbon Dioxide in the
                                                 Carbon in organic
atmosphere
                                                 molecules in plants

                                                            Ingestion
                                                            Digestion
                         respiration in plants              absorption


                                             Carbon in organic                death
                   Respiration in animals
                                             molecules in animals

                                                             Egestion
                                                             death

              Respiration of decomposers
                                             Carbon in dead
                                             organic matter

                                                              fossilisation
    burning
                                             Carbon in fossil fuels
92% of
global CO2
production is
from
respiration
(over which
we have no
control) and
only 2% is
produced by
all forms of
transport!
Atmospheric CO2
levels are rising
steadily (see right), but
there is no way that
humanity can stop this
rise and even more
uncertainty as to the
consequences of this
rise.

Plant growth will
certainly increase, as
lack of CO2 is the
limiting factor for
photosynthesis
throughout the world (in
summer, anyway).
         The Carbon Cycle
• Explain what is meant by a carbon source
  and a carbon sink
• Explain how humans influence the carbon
  cycle

				
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