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Catalyst
1. Where does all energy in the food web begin?
2. Name the producer3. Name two primary
consumers.4. What would happen to
the population size of bluebirds if the snails were wiped out by a disease?
What If…?
Key Point #2: We can use food webs to predict what will happen when we introduce/take away a species Three important interactions for you to
learn.
What do you think will happen to the rabbits, if all the vegetation is destroyed?
If a population loses ALL of its food sources, it will become extinct.
Food Web Interactions
What do you think will happen to the cougar, if all of the deer die?
If a population loses SOME of its food sources, it will decrease in size.
Food Web Interactions
What do you think will happen to the mice, if all of the foxes are eaten by the cougars?
If a population loses its predators, it will increase in size.
Food Web Interactions
Guided Practice (GP) 2
What will happen to the mouse population, if a disease kills all the plants?
A. All will go extinct
B. Increase in sizeC. Decrease in sizeD. Reproduce more
Guided Practice (GP) 2
Imagine that a bobcat enters the ecosystem. Bobcats eat insectivorous birds. What will happen to the fox population?
A. All will go extinct
B. Increase in size
C. Decrease in size
D. Move elsewhere
Guided Practice (GP) 2
Imagine that a disease kills all of the snakes in the ecosystem. What will happen to predaceous insect population?
A. All will go extinct
B. Increase in size
C. Decrease in size
D. Stop eating herbivorous insects
Guided Practice (GP) 2
What will happen to the squirrel population, if a cow wanders by and eats all the plants?
A. All will go extinct
B. Increase in sizeC. Decrease in sizeD. Start eating
toads
Guided Practice (GP) 2
What will happen to the rabbit population, if a drought kills all the plants?
A. All will go extinct
B. Increase in sizeC. Decrease in
sizeD. Eat foxes
Guided Practice (GP) 2
Imagine that a hunter kills all of the hawks and owls in the ecosystem. What will happen to the seed-eating bird population?
A. All will go extinct
B. Increase in size
C. Decrease in size
D. Begin eating spiders
Guided Practice (GP) 2
Pretend that a falcon enters the ecosystem. Falcons eat toads. What will happen to the snake population?
A. All will go extinct
B. Increase in size
C. Decrease in size
D. Stop eating toads
Guided Practice (GP) 2
Imagine that a population of bears wanders into the ecosystem. Bears eat foxes. What will happen to the squirrel population?
A. All will go extinct
B. Increase in size
C. Decrease in size
D. Move elsewhere
Key Point Wrap-Up
KP#1: A food web shows all the feeding relationships in an ecosystem.
KP#2: We can use a food web to predict what will happen when we introduce/take away a species If a population loses ALL of its food sources, it
will become extinct. If a population loses SOME of its food sources,
it will decrease in size. If a population loses its predators, it will
increase in size.
Review Questions
1. What animal does the elk transfer its energy to?
2. From which level does level B get its energy?
3. What level does level B pass its energy to?
4. In which level does all of the energy end up?
Energy reminders
Energy travels UP the food chain
All energy begins with the sun Producers get their energy from the sun
Primary consumers get their energy from the producers
Key Point #1:
Only 10% of the energy is passed from one level of the food web to the next Called the “10% rule” The other 90% of energy escapes as heat energy
Which level will have the LARGEST amount of energy?
Which level will have the SMALLEST amount of energy?
Key Point #2: Energy and biomass levels dramatically decrease as you move up the food chain
Energy and Biomass Pyramids
Energy: the ability to do work, comes from Sun or what you eat
Biomass: the total weight made up in plant or animal tissue Bio-: living Mass-: amount of
matter
Biomass pyramid
Larger # of living things
Larger # of living things
Larger biomassLarger biomass
More energy(from what??)
More energy(from what??)
In a mountain ecosystem you will find…
• Millions of blades of grass• One or two bears
Why are there so few bears???
Why are there so FEW bears?
What percent of energy moves from level A to level B?
Which level has the largest amount of energy?
Which level has the least amount of energy?
1. Which organism will have the HIGHEST amount of energy in the food web?
a. Insectsb. Cougarc. Foxd. Vegetation
2. Which organism will have the LOWEST amount of energy in the food web?
a. Insectsb. Cougarc. Deerd. Vegetation
3. Which organism will have the HIGHEST biomass in the food web?
a. Insectsb. Cougarc. Foxd. Vegetation
4. Which organism will have the HIGHEST amount of energy in the food web?
a. Plantsb. Rabbitsc. Spiderd. Snake
5. Which organism will have the LOWEST amount of energy in the food web?
a. Plantsb. Rabbitsc. Spiderd. Snake
6. Which organism will have the HIGHEST biomass in the food web?
a. Plantsb. Rabbitsc. Spiderd. Snake
Stations
Work in partner pairs4 Stations
Follow station directions Station 2 requires no writing
Stay focused
Exit Questions
1. Describe in a complete sentence what is meant by the “10% rule.”
2. What happens to the energy that is not transferred from one level of the food web to the next?3. In the food web above, which level has the greatest energy?
4. Which level has the least biomass?