Food Chains Lesson

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Transcript Food Chains Lesson

Recall that matter cycles through an ecosystem, changing
form constantly.
Like matter, energy also flows through an ecosystem...
…but it does not cycle.
Food Chain
Diagram that shows the flow of energy in one direction
through an ecosystem; energy is transferred when organisms
eat or get eaten.
The food chain could also look like this:
Or, like this:
Unlike matter, energy does not cycle.
This makes sense, because the Sun doesn’t eat the fungus…
Land-Based Food Chain
Autotroph
Light
energy
Photo.
Heterotroph
Eating
Plant
Rabbit
Heterotroph
Eating
Fox
Heterotroph
Death
Fungus
Energy does not cycle for two reasons.
1. Some of the energy is used up when living things grow,
move, do active transport, etc.
2. Also, some of the energy is lost as heat.
Only about 10% of energy is passed on when living things get
eaten.
Only 10% of energy is passed on!
Get dressed
Walk to school
Heat
500
calories
50
calories
Run
Mate
Heat
5
calories
Top of the
food chain
Roar
Build a nest
Heat
.5
calories
No energy left
to pass on!
Land-Based Food Chain
Autotroph
Light
energy
Photo.
Heterotroph
Eating
Plant
Rabbit
2000 cal.
200 cal.
Heterotroph
Eating
Fox
20 cal.
Heterotroph
Death
Fungus
2 cal.
Trophic Level
Auto and
Hetero
Each step in a food chain, not including the Sun.
Land-Based Food Chain
4 trophic levels
Autotroph
Light
energy
Photo.
Heterotroph
Eating
Plant
Rabbit
200 cal.
20 cal.
Heterotroph
Eating
Fox
2 cal.
Heterotroph
Death
Fungus
.2 cal.
Since energy is used up/lost as heat, food chains generally do
not have more than 5 trophic levels.
Ocean food chains are quite different from the ones on land.
PLANKTON
Microscopic
organisms
(Unicellular, or very small
multicellular organisms)
Plankton in a drop of ocean water:
Phyto/photo = light
Zoo = animal
Autotroph
Ocean Food Chain
5 trophic levels
Hetero.
Hetero.
eating
Light Photo. Phyto- eating zooSmall
energy
plankton
plankton
fish
60,000 cal
6000 cal
600 cal
Hetero.
eating
Large fish/
mammals
60 cal
Hetero.
Death
Bacteria
6 cal
Not all food chains depend on light energy.
Chemosynthesis
Chemicals
Chemical reaction performed by deep-sea bacteria ; similar to
photosynthesis, but uses chemicals as an energy source
instead of light.
Chemosynthetic Food Chain
Construct a chemosynthetic food chain using the items
below:
Giant tube worms
Chemosynthetic
bacteria
Chemicals
Zoarcid fish
Decomposing
bacteria
Chemosynthetic Food Chain
4 trophic levels
Autotroph
Chemicals
Chemo.
Chemosynthetic
Bacteria
400 cal.
Heterotroph
Eating
Giant
tube worms
40 cal.
Heterotroph
Eating
Zoarcid
fish
4 cal.
Dying
Heterotroph
Decomposing
bacteria
.4