Download Lecture - Balsiger

Energy
Pyramids
How energy moves
through a food web
III) Energy Pyramids (Introduction and Practice)
Write these questions down and leave 2-4 lines to
respond to each question during the PowerPoint:
1) Where does the energy that you use come from
and how do you get it?
2) How do you use this energy and what does it
become?
3) Explain the 10% rule:
4) What are decomposers and detritivores and why
are they not on the energy pyramid?
Where does the energy
come from?
• The Sun! Solar energy drives
almost all ecosystems
• Solar energy is converted to
chemical energy (sugars) by
producers (plants, algae, some
bacteria)
• Non-producers get their
chemical energy by eating other
living things (dead or alive)
Why do organisms need energy?
Energy is required for cellular
processes
• growth
• repair
• making new substances
• transporting substances
• reproduction
What happens to the energy?
• The energy used by cells is called
chemical energy
• Chemical energy used by cells is:
– Converted to another type of
chemical energy, or
– Converted to thermal energy (heat)
• The heat is released into the
environment
• In some animals this heat loss is
obvious, e.g. someone who is
running and using a lot of chemical
energy will feel warm
•But all organisms, even
plants and other “cold”
organisms, release some
heat
Chemical Energy &
Trophic Levels
• Trophic levels
are often
described in
pyramids
• Producers are
always at the
bottom
• The primary consumers are next
• Then the secondary consumers,
tertiary consumers, etc.
10% rule:
• 90% of the energy available to a
trophic level is not used for growth.
• This 90% is used or wasted by the
consumers and is no longer available
to the next level of consumers who
eat them.
• Scientists have found roughly 10% of
the available food energy is used to
form biomass by the consumer
• Kcal is kilo calorie, a unit of energy
• The chemical energy at each level is only
10% of the previous level
Kcal
Kcal
Kcal
Kcal
How many Kcals?
Secondary
Consumer
47.5 Kcals
How many Kcals?
Primary
Consumers
475 Kcals
4,750 Kcals
Producers
If the Primary
Consumers have 3,200
kcals of energy, how
much energy do the
producers have?
Hint: 3,200 is 10%
of what?
That’s right!
The producers have
about 32,000 kcals
of energy.
More Levels:
Detritivores
• Detritivores break down
dead material into
smaller pieces
• Ex: Things found in the
leaf litter! earthworms,
vultures, hyenas,
millipedes, pill bugs,
dung beetles….
Decomposers/Detritivores
• Decomposers and detritivores do
not “fit” into the energy pyramids
because they do not follow the
10% pattern
• We cannot easily predict the
amount of energy present in the
decomposer/detritivore trophic
level because the eat any organic
matter they find.