Energy in Ecosystems
• Producers
– Basis of an ecosystem’s energy
– Autotrophs: perform
photosynthesis to make sugars
– Chemotrophs: Bacteria which
use minerals from deep-sea
vents to make energy
• Consumers
– Heterotrophs: Consumes
others for energy
– Omnivores, herbivores,
carnivores, decomposers,
detritivores
• Defined: Feeding level of an
ecosystem
• Trophic levels consist of
producers, consumers, and
decomposers
• ~ 10% of energy is passed to the
next level
– ~ 90% is used by the organism or
lost as heat
– Food chains contain few trophic
levels
• 1st trophic level = Producers
• Autotrophs (perform photosynthesis)
• Bottom (basis) of food chain
• Ex: Plants, algae, cyanobacteria
• 2nd trophic level = Primary consumers
• Feed on producers
• Herbivores (plant eaters)
• 3rd trophic level = Secondary consumers
• Feed on primary consumers
• Omnivores and carnivores
• 4th trophic level = Tertiary consumers
• Feed on secondary consumers
• Omnivores and carnivores
• 5th trophic level = Quaternary consumers
• Feed on Tertiary consumers
• Omnivores and carnivores
• Rarely shown on food
chains
• Feed on any food chain
level when organisms
die
• Detritivores:
Feed/ingest dead matter
• Decomposers: secrete
enzymes to break down
dead matter and then
absorb the nutrients
What’s wrong with this food chain?
The arrows are pointing the wrong direction.
This implies that
the plant eats the
grasshopper.
What’s wrong with this food chain?
The arrows are pointing the wrong direction.
This implies that
the grasshopper
eats the mouse.
What’s wrong with this food chain?
The arrows are pointing the wrong direction.
This implies that
the mouse eats
the snake.
What’s wrong with this food chain?
The arrows are pointing the wrong direction.
This implies that
the snake eats the
hawk.
On your paper fix the arrows so
they show the correct direction
energy travels…
Now the arrows show the direction that energy is
passed up the food chain.
• Defined: diagram that compares energy used by producers & other
organisms on trophic levels.
• Label the tropic levels in this energy pyramid
• Defined: Group of
interrelated food
chains
• Arrows show direction
energy (nutrients)
travel
Analysis:
Highlight a
food chain
from this
food web.
Then label
each
trophic
level.
Tertiary consumer
Secondary consumer
Primary consumer
producer
Analysis:
Highlight a
food chain
from this
food web.
Then label
each Tertiary consumer
trophic
level.
Secondary
consumer
Primary consumer
producer
Quaternary consumer
Analysis
• What could
happen if the
grasshoppers die
out due to
pesticide use?
Blue jay death
(less spiders to eat)
Spider death
(no more
grasshoppers to eat)
Owl death
(less blue
jays to eat)
Squirrel increase
(less owls
hunting them)
YouTube Food Chain Video
Review
1. How many trophic levels are in the following food chain?
Apple tree  Worms  Blue Jay  Owl
2. If the tree in the example above makes 15,000 calories of energy
from photosynthesis, how much energy is available for each other
trophic level?
3. In the food chain above, which is the producer?
4. In the food chain above, which is the primary consumer?
5. In the food chain above, which is the tertiary consumer?
6. Which level consumer are herbivores known as?
7. What is the lowest consumer level possible for a carnivore?
8. Examine the food web on the previous slides. Find a complete food
chain that is 6 trophic levels from start to finish.