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?

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.

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

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

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

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

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

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

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

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

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

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

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

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 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?

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

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 biomass More energy (from what??) Larger # of living things Larger biomass

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? 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

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?

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

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

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

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

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

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

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

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?