Food Pyramids
 Each
trophic level is smaller
than the one on which it
depends, giving a pyramid
shape. The base of the
pyramid represents the
autotrophs, or first trophic
level. Higher trophic levels are
layered on top on one another.
Although you may not
see it it’s important to
notice that the initial
source of energy for an
ecological pyramid is
energy from the SUN
Numbers Pyramid
 Shows
the number of
organisms at each level.
 Represents the fact that there
are fewer individuals at each
successive feeding level
Biomass Pyramid
Show
the mass of
organisms at each level.
 Represent
the fact that there is
less total mass found in each
successive level
Importance of Solar Energy
All
Organisms require
energy for metabolism
What
is the original source
of energy in the biosphere?
Energy Pyramid
 Shows
the amount of energy
stored at each level. The general
rule of thumb is only 10% of the
total energy is passed on to the
next trophic level.
 This energy loss can be
represented by a Pyramid of
Energy
Pyramid of Energy
Energy Transfer
 As
energy is transferred from
one organism to another in a
food chain or web, a large
fraction of the original energy
is lost.
 In the form of what?
 At
each level of the pyramid the
smaller space represents the
lesser amount of energy
P
 1C
 2C
 3C
100% of energy for metabolism
10% of energy for metabolism
1% of energy for metabolism
0.1% if energy for metabolism
 How
is this going to affect the higher
trophic levels?
 Why
would we be more energy efficient as
humans to not eat meat, but to eat “lower
on the food chain” and eat producers?
 It’s
important to compare the relative
energy output expended by an organism
in obtaining food to the energy gained
from the food.
 What
are some different strategies used
by organisms to balance the energy
expended to obtain food to the energy
gained from food?