Class Notes 5: Energy Flow in
Ecosystems
I. Energy Flow
A. Ecologists trace the flow of energy through
communities to discover nutritional
relationships
B. The sun is the ultimate source of energy
that fuels life.
C. Flow of energy
SunAutotrophHeterotrophDecomposer
II. Autotrophs
A. Autotrophs are the producers of their own
nutrients
Example: plants, algae
B. Plants use the sun’s energy to make food in
photosynthesis
III. Heterotrophs
A. Heterotrophs are consumers incapable of
producing their own food
B. Types of heterotrophs include:
1.
2.
3.
4.
Herbivore: feed on plants only
Carnivore: feed on other animals
Omnivore: feed on plants and animals
Decomposer: break down and absorb nutrients from
dead organisms (fungi, bacteria)
Which organism is the autotroph? Which is the
herbivore? Which one is the omnivore?
IV. How ecologists depict
energy flow:
Types of models to use:
A. Food chain: simplest, use arrows to indicate direction of
energy transfer
ex. grassmousesnakehawk
B. Food web:expresses all possible feeding relationships at
each level of a community
(more realistic,
most organisms depend
on more than one food
source)
c. Pyramid of Energy
1.The base represents
producers.
2. At each level, less
energy is available.
3. 90% of energy is lost
to the ecosystem as
heat.
4. Only 10% of energy
goes to the next level
Summary
List the different ways organisms can obtain
energy. What are some ways scientists show
energy flow?