Ecological Pyramids
& the 10% Rule
The Laws of Thermodynamics and
FOOD CHAINS !
2nd Order CARNIVORES
The
10 %
RULE !
The maximum amount of
ENERGY that passes from one
trophic level to the next is
10%.
90% of the ENERGY at each
trophic level is used to keep the
organisms alive and is
converted to HEAT.
Starts
with the SUN.
•The total mass of the organic matter at
each trophic level is called biomass
•Biomass = potential energy – energy that is
to be eaten and used.
•The transfer of energy from one level to
another is very inefficient (10% Law)
Producers are the BASE
of the pyramid of biomass
because
their ENERGY comes
directly
from the SUN.
HERBIVORES
exist on only 10%
of the ENERGY
from PRODUCERS.
90 % of
energy
they make
is used to
keep them
alive =
lost as
heat
10 %
transferred
1st O. Carnivores exist on 10%
of energy from HERBIVORES.
90 % of
energy
they make
is used to
keep them
alive =
lost as
heat
2°
Consumers
10 %
transferred
90 % of
energy
they make
is used to
keep them
alive =
lost as
heat
There isn’t much
ENERGY left near the top.
3°
10 %
CONSUMERS transferred
2°
CONSUMERS
90 % of
energy
they make
is used to
keep them
alive =
lost as
heat
3°
CONSUMERS
2°
CONSUMERS
Few top
carnivores.
Each needs to
eat a LOT
because so
much Energy
has been lost.
Ecological Pyramid – a different view
• Which level
• Which level
organisms?
• Which level
organisms?
• Which level
has the most energy?
has the most
has the least
has the least energy?
Pyramid of
ENERGY
0.01% (or
5 joules)
3°
CONSUMERS
2°
CONSUMERS
...is used to help
predict amount of
energy available to
each organism.
0.1%
(or 50 joules)
stored in 3°
1% (or 500
joules) stored in
2°
10% (or 5000
joules) stored in 1°
100% (or 50,000
joules) is stored.
Pyramid of
BIOMASS
0.1 g/m3
3°
CONSUMERS
2°
CONSUMERS
...is used to help
predict MASS
of organisms that an
ecosystem can
sustain.
1 g/m3
10 g/m3
100 g/m3
1000 g/m3
Pyramid of
Numbers
...is used to help
predict POPULATION
SIZE of organisms
that an ecosystem
can sustain.
1
3°
CONSUMERS
2°
CONSUMERS
10
100
1,000
10,000
20,000 kg
For a 20 kg.
halibut, ______ kg.
of phytoplankton
are necessary !
2,000 kg
200 kg
20 kg
2nd Order CARNIVORES
20 kg
For every 20 kg of
halibut, how many
kgs of sealion
can be supported ?
?
20 kg
If a large male sea
lion has a mass of
200kg, how many
20kg halibut does
it need to eat?
For every 20 kg of
halibut, 2 kg.
of sea lion
can be supported !
2 kg
5th trophic level
3°
CONSUMERS
2°
CONSUMERS
4th trophic level
3rd trophic level
2nd trophic level
1st trophic level
REVIEW CHECKPOINT:
1. What is the 10% rule ?
2. Where does most of the ENERGY go
at each trophic level ?
3. What are the 3 types of pyramids?
4. If there are 15,000 kg of anchovies,
tell how many kg are predicted:
a. Zooplankton
c. Halibut
b. Phytoplankton d. Sea lion
Place these organisms into a pyramid
of numbers:
50 caterpilars
5 robins
1 oak tree
What do you notice about this
pyramid’s shape? What type of
pyramid would be more useful in this
food chain?