Feeding relationships
Food chains
We will be talking about the transfer of
energy through an ecosystem- food
chain
Rabbit, fox & grass
Source of energy
• The original source of all energy is the sun
• Green plants and algae produce food
– They are called producers
• Producers produce their own food from nonliving substances such as light.
• What is the name of the
process where plants get
energy from the sun?
• Our source of energy?
2
Flow of Energy
• Energy only moves in one
direction within the food
chain.
• The links within the food chain are known as
‘trophic levels’
• Organisms that can’t produce their own food are
know as consumers.
3
Flow of Energy
Producers are green plants and algae – eg. grass
First order consumers- herbivores- eg. grass hoppers
Second order consumers – carnivores- eg. toad
Third order consumers are carnivores – eg. snake
*it is possible for an animal to belong to more than
one group.
4
Flow of Energy
Food Pyramid
• Where do producers gain
their energy?
• When consumers eat
producers, this energy is
passed up the food chain.
• Some of this energy is lost
at each stage (eg. heat,
wastes). This means that
not all the energy from the
sun reaches the top
If energy is lost at each level, how
does energy reach the top
consumer
consumer?
5
Food chain: a flow of energy in a habitat
Grass is eaten by
Rabbits which are eaten by
Owls
Grass
Rabbit
Owl
The arrows show the direction of energy
flow.
Flow of Energy
• Examples of food chains
– Owl, mouse, grass & snake
– Leaves, frog, slug & heron
– Plant, bird, spider, cat & ants
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Pondweed
small fish
Insect larvae
Heron
Pondweed
Insect
larvae
Minnow
(little fish)
Heron
Food webs
• Sometimes we need to join a number of food
chains together.
• This is when many animals eat more than one
kind of food.
-What does the hawk
eat?
-Which animals are the
herbivores?
-Are these 1st, 2nd or 3rd
line consumers?
How many food chains are there now?
Weasel
Plant
matter
Grass
Shrew
Owl
Rabbit
Worm Snail
Hedgehog
Fox
Write down as many food chains you can find within
this web. What do you start with in a food chain?
Plant
matter
Shrew
Weasel
Fox
Grass
Shrew
Plant
matter
Weasel
Fox
Shrew
Owl
Grass
Shrew
Owl
Plant
matter
Worm
Hedgehog
Fox
Plant
matter
Snail
Hedgehog
Fox
Grass
Rabbit
Fox
Grass
Rabbit
Fox
Decomposers
• Decomposers break down and recycle matter
within their ecosystem, so that plants can
reuse the nutrients.
• Decomposers return nutrients from dead
plants and animals into the soil  plants.
• Examples: bacteria, fungi & worms.
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Detritivores
• Detritivores eat small particles of dead plant
and animal matter. They also eat animal
waste products. Detritivores include: worms,
insect larvae, snails and some crustaceans.