FOOD CHAINS
& WEBS
the ultimate energy source
Energy Flow in Ecosystems
Energy flows from where into the
biological world?
Energy Flow
• How does the sun’s energy enter
the biological world?
• What is photosynthesis?
Energy Flow
• The sun’s energy flows into organisms
that can change the sunlight into food
then into organisms that eat them.
• This flow is:
sunlight
producer
consumer 1
consumer 2
Word to Know
omnivore
PRODUCERS
• What are producers?
• Autotrophs that trap solar energy into
organic molecules during photosynthesis;
can produce their own food
• Ex. Plants, algae and some bacteria
``
sunlight
producer
consumer 1
consumer 2
CONSUMERS
• What are consumers?
• Heterotrophs that eat other organisms
to obtain energy
• Examples: deer, rabbits, cows, mice,
lions, humans, hawks, snakes
sunlight
producer
consumer 1
consumer 2
HERBIVORES
• What are herbivores?
• Organisms that eat
plants
• Primary Consumers
• Ex. Cows, caterpillars, bunnies
sunlight
producer
consumer 1
consumer 2
CARNIVORES
• What are carnivores?
• Organisms that eat meat (other
animals/consumers)
• Secondary Consumers
• Ex. tigers, wolves, snakes, hawks
sunlight
producer
consumer 1
consumer 2
TOP CARNIVORES
• What is a top-level carnivore?
• Top-level carnivores eat secondary
consumers; usually nothing feeds
on them
• Ex. killer whale eating a sea
lion or hawk eating a snake.
consumer 3
sunlight
producer
consumer 1
consumer 2
OMNIVORES
• What are omnivores?
• Consumers that eat both plants and
animals
• Primary and Secondary Consumers
• Ex. bears and humans
Where do all
the dead things go?
• They are eaten.
YUMMMM!
• They decay.
SMELLY!
Detritivore vs Decomposers
• Detritivores and decomposers both feed
on the remains of dead plants and
animals and other dead matter (detritus)
• They rely on dead tissues for nutrients.
detritivore
decomposer
Detritivore vs Decomposers
• Detritivores eat
the remains of
dead plants and
animals
Crabs, mites,
earthworms,
snails
• Decomposers
breakdown
(decay) organic
matter and feed
on it
Bacteria & fungi
Detritivore vs Decomposers
• What is a scavenger?
• A scavengers is a
type of detritivore
that feeds on
carrion (dead
animal remains).
Ex. vultures, sharks,
maggots, hyenas
Detritivore vs Decomposers
• Why would they be called the
environmental “recyclers”?
• They decompose excrement, dead bodies
and leaf litter, returning nutrients
to the physical
environment.
decomposer
sunlight
producer
consumer 1
consumer 3
consumer 2
Energy Flow
• The series of steps in which
organisms transfer energy by eating
and being eaten is called a Food
Chain
sunlight
producer
consumer 1
consumer 2
Food Chains & Food Webs
• The steps in the transfer of energy from
organism to organism in feeding
relationships are called Trophic Levels.
• How does a food chain describe this path of
energy? (arrows)
producer
consumer 1
consumer 2
consumer 3
Food Chains & Food Webs
• Name the number of the trophic levels in
the food chain below.
• How do the trophic level numbers
correspond with the “eating terms”?
producer
Trophic
Level
1
consumer 1
2
consumer 2
consumer 3
3
4
Food Chains & Food Webs
• What important energy transfer is not
shown in a food chain?
• Why is it that some energy is lost from
one level to the next level?
• How much energy is actually passed on to
the next level? (rule of thumb)
producer
consumer 1
consumer 2
consumer 3
Food Chains & Food Webs
• What vital “recycler” is not shown in
this food chain?
• Upon which organism(s) would it
feed?
decomposer
producer
consumer 1
consumer 2
consumer 3
Food Chains & Food Webs
• If all of the snakes in this chain died, what
would happen to the hawk?
• To the decomposers?
decomposer
producer
consumer 1
consumer 2
consumer 3
Food Chains & Food Webs
• Most organisms feed on more than one
trophic level and feed on several different
species at each trophic level. This is a food
web.
Antarctic Food Web
Making a Food Web
• Use these organisms for Food Chains and
Food Web Practice worksheet.
Ecological
Pyramids
Ecological Pyramids
• Instead of
representing
trophic levels in a
food web, an
ecological
pyramid can be
used.
Hawk
(1 kcal)
5
4
Snake (10 kcal)
Frog (100 kcal)
3
Grasshopper (1,000 kcal)
2
Grass (10,000 kcal)
1
Ecological Pyramids
• Does this pyramid represent a food chain
or web?
Hawk
(1 kcal)
• How could
this pyramid
be changed to
represent a
food web?
5
4
Snake (10 kcal)
Frog (100 kcal)
3
Grasshopper (1,000 kcal)
2
Grass (10,000 kcal)
1
Ecological Pyramids
Hawk
(1 kcal)
• What do the big
numbers
represent?
5
4
Snake (10 kcal)
Frog (100 kcal)
3
• What does the
kcal mean?
Grasshopper (1,000 kcal)
2
Grass (10,000 kcal)
1
Pyramid of Energy
• What happens to the energy as you go
up?
Hawk
(1 kcal)
• How much
energy is
available for
the next level?
(What %)
5
4
Snake (10 kcal)
Frog (100 kcal)
3
Grasshopper (1,000 kcal)
2
Grass (10,000 kcal)
1
Pyramid of Energy
Pyramids of
energy show
the relative
amount of
energy
available at
each trophic
level of a food
chain or food
web.
Hawk
(1 kcal)
5
4
Snake (10 kcal)
Frog (100 kcal)
3
Grasshopper (1,000 kcal)
2
Grass (10,000 kcal)
1
Pyramid of Energy
Pyramid of Energy
Ecological Pyramids
• How is this pyramid different from the
previous ones?
• What could the
multiple
pictures of the
species at each
level represent?
Pyramid of Biomass
Biomass-the total
amount of living
tissue within a given
trophic level.
A pyramid of
biomass illustrates
the relative amount
of living organic
matter available at
each trophic level
Pyramid of Biomass
• What information would this pyramid
include if it were a pyramid of
biomass?
• How do they
get a number
total for the
biomass of a
population?
Pyramid of Biomass
Pyramid of Biomass
Pyramid of Numbers
A pyramid of
numbers shows
the relative
number of
individual
organisms at each
trophic level.
Pyramid of Numbers
• What information would this pyramid
include if it were a pyramid of
numbers?
• How do they
get a number
total for a
population of
organisms?
Pyramid of Numbers
Pyramid of Numbers
Pyramids of Aquatic Ecosystems
• Numbers
• Biomass
Phytoplankton are microscopic and weigh
very little
• Energy
Pyramids of Temperate Forests
• Numbers
Trees are huge but not as numerous as
many smaller forest creatures.
• Biomass
• Energy