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Food Chains
Grass Mouse Snake Kookaburra
Food Chains
• A FOOD CHAIN shows energy flow through an
ecosystem
Grass Mouse Snake Kookaburra
• It can also be shown through a more complex
diagram – a FOOD WEB
Food Webs
Where does the energy come from?
• Food webs also show the energy flow through
an ecosystem
• Food webs are more realistic because:
Grass Mouse Snake Kookaburra
• In our simple food chain, the mouse obtains
energy from the grass, the snake obtains
energy from the mouse, and the kookaburra
from the snake.
• What would happen if one of these organisms
was removed from the food chain?
• Where does the grass get its energy from?
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Energy from the sun
Consumers
• PRODUCERS or AUTOTROPHS capture radiant
energy from the sun and convert it to
chemical energy (glucose)
• CONSUMERS are
• This process is called:
• Examples of consumers:
• Examples of producers:
Types of Consumers
• Primary consumers: mainly feed on producers
– E.g. caterpillars
• Secondary consumers: feed on primary
consumers
Types of Consumers
• Identify primary, secondary and tertiary
consumers in this food chain:
Grass Mouse Snake Kookaburra
– E.g. Birds that eat caterpillars
• Tertiary consumers or Top carnivores:
– E.g. Eagles that eat the birds feeding on
caterpillars
Types of Consumers
• Identify primary, secondary and tertiary
consumers in this food web:
Trophic Levels
• We can also identify organisms in an
ecosystem by their TROPHIC LEVEL (or feeding
level)
• Producers – first trophic level
• Primary consumers – second trophic level
• Secondary consumers – third trophic level
• Tertiary consumers – fourth trophic level
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Trophic Levels
• Identify the trophic levels of each organism in
the following food chain:
Types of Consumers
Trophic
Level
First
Organisms at that level
Second
Primary consumers
(herbivores)
Third
Secondary consumers
(carnivores)
Tertiary consumers (top
carnivores)
Producers
Grass Mouse Snake Kookaburra
Fourth
Energy Flow
• Energy flowing
through an
ecosystem originates
from the sun
• Producers convert
this energy to
chemical energy
• What happens to the
energy made by
producers?
The 10% Rule
Source of chemical
energy/food
Make organic matter
(food) from inorganic
substances using energy
from sunlight
Eat plants or other
producers
Eat herbivores
Eat predators
Energy Flow
• Each organism in the food chain uses
up some energy to carry out bodily
functions
• Energy is lost as
heat
Heat
Energy
• Energy is stored by the
organism for later use
Energy Flow Implications
• The amount of energy passed through a food
chain decreases with each trophic level
• Therefore, the higher the trophic level of an
organism, the more it needs to eat
• The number of trophic levels in ecosystems is
limited
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