1. Catalyst Where does all energy in the food web begin?
Name the producer
Name two primary consumers.
What would happen to the population size of bluebirds if the snails were wiped out by a disease?

2. 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.

3. Food Web Interactions
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.
Technically extirpated (extirpation = localized extinction), but that isn’t an important nuance for them to learn until college. 3

4. 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. 4

5. 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. 5

6. Guided Practice (GP) 2
What will happen to the mouse population, if a disease kills all the plants?
All will go extinct
Increase in size
Decrease in size
Reproduce more A 6

7. Guided Practice (GP) 2
Imagine that a bobcat enters the ecosystem. Bobcats eat insectivorous birds. What will happen to the fox population?
All will go extinct
Increase in size
Decrease in size
Move elsewhere C 7

8. Guided Practice (GP) 2
Imagine that a disease kills all of the snakes in the ecosystem. What will happen to predaceous insect population?
All will go extinct
Increase in size
Decrease in size
Stop eating herbivorous insects B 8

9. Guided Practice (GP) 2
What will happen to the squirrel population, if a cow wanders by and eats all the plants?
All will go extinct
Increase in size
Decrease in size
Start eating toads A 9

10. Guided Practice (GP) 2
What will happen to the rabbit population, if a drought kills all the plants?
All will go extinct
Increase in size
Decrease in size
Eat foxes A 10

11. 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?
All will go extinct
Increase in size
Decrease in size
Begin eating spiders B 11

12. Guided Practice (GP) 2
Pretend that a falcon enters the ecosystem. Falcons eat toads. What will happen to the snake population?
All will go extinct
Increase in size
Decrease in size
Stop eating toads C 12

13. Guided Practice (GP) 2
Imagine that a population of bears wanders into the ecosystem. Bears eat foxes. What will happen to the squirrel population?
All will go extinct
Increase in size
Decrease in size
Move elsewhere B 13

14. 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.

15. Review Questions What animal does the elk transfer its energy to?
From which level does level B get its energy?
What level does level B pass its energy to?
In which level does all of the energy end up?

16. Energy travels UP the food chain All energy begins with the sun
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

17. 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

18. Which level will have the LARGEST amount of energy?
Which level will have the SMALLEST amount of energy?

19. Key Point #2:
Energy and biomass levels dramatically decrease as you move up the food chain

20. 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

21. Biomass pyramid Larger biomass More energy (from what??)
Larger # of living things
Larger biomass

22. In a mountain ecosystem you will find…
Millions of blades of grass
One or two bears
Why are there so few bears???

23. Why are there so FEW bears?
Have students explain that bears are located high in the food chain. Bears receive relatively little energy from the food chain. As a result, there is a low number of bears in the population 23

24. 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?

25. Which organism will have the HIGHEST amount of energy in the food web?
Insects
Cougar
Fox
Vegetation
Mini-practice. You could use whiteboards. Or a think-pair-share??? 25

26. 2. Which organism will have the LOWEST amount of energy in the food web?
Insects
Cougar
Deer
Vegetation
Mini-practice. You could use whiteboards. Or a think-pair-share??? 26

27. 3. Which organism will have the HIGHEST biomass in the food web?
Insects
Cougar
Fox
Vegetation
Mini-practice. You could use whiteboards. Or a think-pair-share??? 27

28. 4. Which organism will have the HIGHEST amount of energy in the food web?
Plants
Rabbits
Spider
Snake

29. 5. Which organism will have the LOWEST amount of energy in the food web?
Plants
Rabbits
Spider
Snake

30. 6. Which organism will have the HIGHEST biomass in the food web?
Plants
Rabbits
Spider
Snake

31. Stations Work in partner pairs 4 Stations Stay focused
Follow station directions
Station 2 requires no writing
Stay focused

32. Exit Questions
Describe in a complete sentence what is meant by the “10% rule.”
What happens to the energy that is not transferred from one level of the food web to the next?
In the food web above, which level has the greatest energy?
Which level has the least biomass?