Food Webs: Land and Water
• Every organism on the planet, including
humans, are connected through a food web.
Producers, Consumers, and
Decomposers
• Producers
• Make their own food using photosynthesis
• Plants, green algae, kelp, phytoplankton
Consumers
• Eat other organisms for food
• Cow, human, eagle
Decomposer
• Break down the remains of other organisms
• Fungi and some bacteria
• Vital to ecosystems because they return
important nutrients to the environment
Consumers are classified by their food
source
• Primary Consumers
– Eat only producers
• A cow eating grass is a primary consumer
• Secondary Consumers
– Eat primary consumers
• Human eating a cow
Grassproducer
Grasshopperprimary
consumer
ToadSecondary
consumer
Food Chain
• Flow of energy from one organism to next in
an ecosystem
• Shows flow of energy from producer, to
different consumers, and finally decomposers
• Shows only one path
Food Chain
Food Web
• Many food chains make up a food web
• Food Web
– Interconnected network of food chains within an
ecosystem
Aquatic Food Web
• Food web showing relationships between
aquatic organisms
Terrestrial food web
• Terrestrial food web
– Food web showing relationships between land
organisms
Terrestrial and Aquatic Food Webs
• They can also be connected
– Bear eating fish out of a river
– Birds diving for fish in lakes and oceans
– Fish eating insects that land on the water
Food Chains and Food Webs
• Trophic Level
– Each feeding level in an ecosystem is located
within a tropic level
– Organisms at each tropic level take in energy from
the organisms they eat
Energy Flow Between OrganismsPyramid
• Within an ecosystem, the energy flow
between trophic levels does not remain
constant
• At each level some animals use the energy
taken in to perform life processes
– Some energy is given off as heat
– Some energy is stored in bones and teeth that
may not be eaten by another animal
Energy Flow between trophic levels
• Only 10% of the energy is passed onto the
next higher trophic level
Energy in an ecosystem can be measured in total
number of animals or combined mass of all
animals
• Increase a level animals increase in size
• Increase a level, animals decrease in number
Review
1. Which of these animals is a primary
consumer? (eats a producer)
A
B
C
2. If the producers in an ecosystem
produce 250,000 kilocalories of
energy, how much energy is available
in the third trophic level?
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A. 5,000 kilocalories
B. 2,500 kilocalories
C. 250 kilocalories
D. 25 kilocalories
2. In a marine food web, which of the
following would get its energy directly
from the sun?
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•
•
A
B
C
D
krill
fish
algae
killer whale
3. Which of these animals is a
secondary consumer?
A
B
C
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4. Which of the following situations
show a terrestrial and aquatic food
web connection
A. A seagull eating an insect on the beach
B. shark eating a tuna
C. seagull eating a fish
D. bear eating a deer
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5. Which of the following situations
show a terrestrial and aquatic food
web connection
A.
B.
C.
D.
A furry bear eating a tasty squirrel
An awesome human eating a slow deer
A swift pelican eating a large tuna
A frisky shark snacking on a cute dolphin
Create a terrestrial and aquatic food
web poster.
• Your food web must have 6 animals
• There must be two connections between
terrestrial and aquatic food webs.
• Identify 1 primary consumer, 1 secondary
consumer, and 1 producer.