Food Webs

Write in complete sentences!

Don’t talk during the Catalyst!

Catalyst: Examine the food web to the right.

Tell me at least FIVE conclusions you can draw from it.

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 ReviewHow to Analyze Food WebsActivExpression PracticeIndependent PracticeExit Question

Introduction

First, we studied how individual cells work.

Second, we learned how cells fit together into organisms and reproduce.

Then, we discovered how organisms change (evolve) over long periods time.

Now, we will study how groups of these organisms interact and change the environment around us.

We will also look at how our treatment of the environment threatens the survival of the human species.

This Is Environmental

Science

They eat each other!

Key Point #1: A food web shows all the feeding relationships in an ecosystem.

How Do Organisms Interact?

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.

First, some vocabulary…

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?

Some things to notice…

Guided Practice (GP) 1

The arrow pointing from seed-eating birds to foxes shows that...

A. Foxes eat birdsB. Birds eat foxesC. Foxes and birds

share foodD. Foxes and birds

compete for the same food

Guided Practice (GP) 1

Although it is not shown in this picture, where does all of this food web’s energy begin?

A. The MoonB. The EarthC. The SunD. Fertilizer

Guided Practice (GP) 1

What is the producer in this food web?

A. Hawks and owls

B. SquirrelsC. PlantsD. Spiders

Guided Practice (GP) 1

Which of the following is a secondary consumer in this food web?

A. ToadsB. PlantsC. MiceD. Spiders

Guided Practice (GP) 1

Which two organisms compete for the same food?

A. Hawks & miceB. Plants & toadsC. Rabbits &

spidersD. Foxes & snakes

Which is true?

A. The energy content of the foxes depends on the energy content of the hawks

B. The energy content of the spiders is transferred to the herbivorous insects

C. The energy content of the snakes depends on the energy content of the toads

D. 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.

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 size

C. Decrease in size

D. 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 size

C. Decrease in size

D. 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.

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?

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?

Exit Questions