Your study guide information will be
presented throughout this power point.
Take notes.
Ecological Pyramids:
graphs which
illustrate the
trophic levels in
a community.
AKS covered.
• 10 – compare and contrast food/energy
requirements of different organisms.
• 10a- compare food requirements in Autotrophs
and Heterotrophs.
• 10b- Illustrate food and energy requirements in
Autotrophs and Heterotrophs.
• Bio11b1 – explain the flow of energy through an
ecosystem by arranging the components of a
food chain energy pyramid and biomass pyramid.
Heterotrophs and Autotrophs
Most ecological pyramids are large at the
base and narrow at the top.
This is because every time
that an organism is eaten
by the next trophic level,
some of the energy is lost
as heat.
Less Energy
More Energy
What is the AVERAGE energy loss from
trophic level to trophic level?
The 10% Rule – Energy losses.
• Energy transfers are never 100 percent
efficient.
• 10% of all energy once available at a
trophic level may transfer to the next
trophic level.
• Some energy is lost at each step.
• Limits the number of trophic levels in an
ecosystem.
All Heat in the End.
• At each trophic level, the bulk of the energy
received from the previous level is used in
metabolism.
• This energy is released as heat energy and lost
to the ecosystem.
• Eventually all energy is released as heat.
Add this information to your study guide: Compare
food and energy requirements in Autotrophs and
Heterotrophs.
Autotrophs
Heterotrophs
3 TYPES OF PYRAMIDS:
1. Pyramid of Biomass
2. Pyramid of Energy
3. Pyramid of Numbers
Pyramid of Biomass:
•
Illustrates the amount of biomass in each trophic level
–
•
•
Biomass weight is determined after dehydration.
Shows the amount
of matter lost
between trophic
levels.
Measured in Kg,
grams or pounds
Pyramid of Biomass
Pyramid of Biomass
Pyramid of Biomass
One problem:
They can make a trophic level look like it has more
energy than it really does.
For example:
A bird has a beak, feathers and a skeleton that
would count as biomass even though it does not
contribute to the overall flow of energy into the
next trophic level.
Pyramid of Energy:
• Shows the energy available at each trophic level.
– The size of the blocks represents the proportion of
productivity
– Measured in Joules or Calories
Pyramid of Energy:
• Most of the energy available to the community is in
the 1st trophic level.
• Only 10-20% of the energy is available to the next
trophic level (≈ 90% lost)
Take out the Food
chain you drew in
the computer lab.
Explain the flow of
energy through an
ecosystem using the
food chain you
created. You may use
page 720 in textbook
if you need more
information.
Pyramid of Numbers:
• Illustration of the number of organisms at each
level
What kind
of Pyramid
is this?
Energy, the
trophic levels are
measured in
Kilocalories
Human Population Growth
How can more people be supported on Earth
when there is a limited supply of resources?
It depends on what they are eating…
Human Population Growth
• It requires 10 times as many crops to feed
animals being bred for meat consumption as it
would to feed the same amount of people on
a vegetarian diet!!
• The US could feed 800 million people with the
grain that livestock eat.
US population: 303 million
So Remember!
Ecological (Trophic) Pyramids show:
Energy transfer and more importantly energy
loss in an ecosystem.
Why there are more herbivores than carnivores
in an ecosystem.
Why there are more plants than everything else
combined (they support all other populations).
Add the answers to these questions to
your study guide!!
• Compare and contrast food/energy requirements of
different organisms.
• Compare food requirements in autotrophs and
heterotrophs.
• Draw and illustrate food and energy requirements in
autotrophs and heterotrophs.
• Explain why sunlight is the source of energy for most
food webs.
• Describe in a food web how matter is transferred from
one organism to another and how it can be recycled
between organism and their environments.
And these too.
• What are the roles of a producer, consumer, and
decomposer?
• What is an energy role in an ecosystem? Give an
example of each.
• How is a decomposer different than a scavenger?
• What is the difference between food chains and
food webs? How are they similar?
• Look at the Energy Pyramid on page 722 and be
able to explain how it works.
The End
or is it just the beginning?