Download SNC1D Energy Flow and Ecological Pyramids Note

Energy Flow
Energy - the capacity to do work
All organisms require energy to survive. The source of almost all
energy is radiant energy, which comes from the sun.
How does energy from the sun get converted into chemical
energy used by all organisms?
Photosynthesis
Equation:
carbon dioxide + water + light energy à glucose (sugar) +
oxygen
Organisms that perform photosynthesis are called producers.
Sugar is stored energy. To make stored energy available for use for
both producers and consumers, they undergo Cellular
Respiration.
Equation:
Glucose (sugar) + oxygen à carbon dioxide + water + energy
Energy Flow
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Energy moves from one organisms to another when it is eaten
Only 10% of the energy from one trophic level is transferred to
the next
No organism EVER receives all of the energy from the organism
they just consumed
Each step in this transfer of energy is known as a trophic level
Food Web
q The energy flow from one trophic level to the other is known
as a food chain
q A food chain is simple and direct.
q It involves one organism at each trophic level.
Food chain example:
seed à mouse à cat
Primary (1°) Consumers – eat autotrophs (producers)
Secondary (2°) Consumers – eat the primary consumers
Tertiary (3°) Consumers – eat the secondary consumers
Decomposers – bacteria and fungi that break down dead
organisms and recycle the material back into the environment
Most organisms eat more the JUST one organism. When more
organisms are involved it is known as a FOOD WEB. Food webs
are more complex and involve lots of organisms.
e.g.
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Notice that the arrow points in the direction of the energy
transfer, NOT “what ate what”
Biomass
q The total mass of the organic matter at each trophic level is
called biomass
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Biomass is just another term for potential energy – energy
that is to be eaten and used.
The transfer of energy from one level to another is very
inefficient (only 10%)
Ecological Pyramids
q An ecological pyramid shows the relationship between
consumers and producers at different trophic levels in an
ecosystem by relative amounts of energy or matter
1) Pyramid of Numbers:
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show number of organisms in each trophic level
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usually numbers decrease as one moves up food chain
eg.
5 birds
900 ants
10 000 grass
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sometimes, it does not produce a proper pyramid in all cases
e.g. a tree
1500 lice
5 birds
4000 caterpillars
1
tree
2) Pyramid of Biomass:
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the total mass of the organic matter at each trophic level is
called biomass
Biomass is just another term for potential energy – energy that
is to be eaten and used.
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eg.
2 kg lice
15 kg birds
200 kg caterpillars
2000 kg apple tree
3) Pyramid of Energy:
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shows the total energy of organisms in a food chain
this is the best way to show flow of energy through a food chain
eg.
1 kJ lice
10 kJ birds
100 kJ caterpillars
1000 kJ apple tree
approx. 90% energy is lost with each transfer in the food web