Food Webs Catalyst: Describe evolution in your own words. Solve: Shaq is selling candy, M&M’s and Twix. He sold 48 total candy bars. He sells M&M’s for 2 dollars and Twix for 3 dollars and made 124 dollars total. How many of each bar did he sell? Write in complete sentences! Don’t talk during the Catalyst!

Objective By the end of today, all SWBAT… Analyze food webs by predicting the impact of the loss or gain of an organism

Agenda Catalyst Interims/Progress Reports (signed by Wednesday) Expectations Refresher Carry-on Video Food Webs Practice Exit Q

How Do Organisms Interact? They eat each other! Key Point #1: A food web shows all the feeding relationships in an ecosystem.

First, some vocabulary… Producer: another word for autotroph. Makes its own food through photosynthesis. Consumer: another word for heterotroph. Eats other things for energy. Primary consumer: eats producers. Secondary consumer: eats primary consumers. Tertiary consumer: eats secondary consumers. Note that animals can have multiple roles. The cougar is both a secondary and a tertiary consumer.

Some things to notice… Arrows show how energy flows through the food web Think: they point from one organism INTO the stomach of whatever eats it The most basic level of the food web is the producer. Where does it get its energy from? Foxes eat snakes. Last transition: Prompt kids… they should be able to come up with their answer on their own. Producers get their energy from the sun.

Guided Practice (GP) 1 The arrow pointing from seed-eating birds to foxes shows that... Foxes eat birds Birds eat foxes Foxes and birds share food Foxes and birds compete for the same food Use ActivExpressions if you have them, otherwise whiteboards/sign language. A

Guided Practice (GP) 1 Although it is not shown in this picture, where does all of this food web’s energy begin? The Moon The Earth The Sun Fertilizer C

Guided Practice (GP) 1 What is the producer in this food web? Hawks and owls Squirrels Plants Spiders C

Guided Practice (GP) 1 Which of the following is a secondary consumer in this food web? Toads Plants Mice Spiders D

Guided Practice (GP) 1 Which two organisms compete for the same food? Hawks & mice Plants & toads Rabbits & spiders Foxes & snakes D

Which is true? The energy content of the foxes depends on the energy content of the hawks The energy content of the spiders is transferred to the herbivorous insects The energy content of the snakes depends on the energy content of the toads All of the above are true

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.

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.

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

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

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

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

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

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

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

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

Independent Practice Make your own food web. (You don’t actually have to draw each animal, if you don’t want to. You can just write their names.) Your food web must have at least FOUR producers, TWO primary consumers, ONE secondary consumer, and ONE tertiary consumer. Describe two situations in which an organism enters/leaves your food web. Explain what will happen to the other organisms in your food web as a result. Optional, if time permits. Last year, students blazed through this lesson, even though there are a lot of slides/GP questions.

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.

Exit Questions Use the food web at right to answer the questions below. What animal eats the elk? What would happen to the rabbit population, if all the grass were to be burned down in a fire? Imagine that a population of foxes wanders into this food web, and eats all the mice. What will happen to the cricket population? Mountain lion Extinction Increase in size