Food Webs and Energy Flow

November 9/10

Do Now

• Grab one of our brandy-spankin’ new Trackers • Start working on today’s warm-up:

Why do we eat?

New Class Procedures

• Warm-up/Exit ticket trackers• Class log – If you arrive late– If you leave class for any reason

• New class website: DrMooreScience.com

Grades are updated

• Work is returned to you in your hanging file• You can (and SHOULD) make up any work that

scores less than 75% of its point value

Objective

• Explain why plants are more abundant in ecosystems than top predators.

By the end of class, students will be able to:

Why do we eat?

Why do we eat?

• To gain matter • To gain energy

Matter versus Energy

• Matter is physical stuff • Energy is the ability to change matter

Matter cycles, energy flows

• The Earth does not gain or lose great amounts of matter

• Matter on Earth is recycled

Matter cycles, energy flows

• The Earth gains energy in the form of solar radiation and loses energy as heat

• Energy flows through Earth

Matter versus Energy

• Matter ≠ Energy• But energy can be stored in matter

Why do we eat?

• To gain matter • To gain energy

Why do we eat?

A “Calorie” is a unit of energy

Why do we eat?

In Europe, they use the word “Energy” on their nutrition labels instead of “Calories”

Food webs show the flow of energy through an ecosystem

Arrows show movement of energy(always point to the predator)

Yellowstone National Park Food Web• In each relationship, the arrow points to the predator.

1. Pond algae is eaten by mayflies and cutthroat trout.2. Bearded wheatgrass and sagebrush are eaten by elk, bison,

snowshoe hares, and deer mice.3. Gray willow leaves are eaten by deer mice, elk, and bison.4. Aspen trees are eaten by beavers. The leaves are eaten by elk.5. Mayflies are eaten by harlequin ducks, grizzly bears, and deer

mice.6. The snowshoe hare is eaten by coyotes, wolves, and foxes.7. Cutthroat trout are eaten by bald eagles and grizzly bears.8. Beavers are eaten by coyotes and gray wolves.9. Harlequin ducks are eaten by red foxes and bald eagles.10. Deer mice are eaten by coyotes, red foxes, grizzly bears, and bald

eagles.11. Elk and bison are eaten by coyotes and gray wolves. 12. Gray wolves may also feed on coyotes and red fox.

• What do the arrows show the flow of?• Why are arrows always drawn from prey to

predator?

Some organisms don’t eat anything!

Organisms that make their own food are called..

• Autotrophs or• Primary producers

Organisms that make their own food are called..

• Autotrophs or• Primary producers

Plants produce their own food through PHOTOSYNTHESIS

Organisms that make eat other things for food are called..

• Heterotrophs or• Consumers

Classifying Consumers

• Herbivores eat only plants

Classifying Consumers

• Carnivores eat only animals

Classifying Consumers

• Omnivores eat plants and animals

Classifying Consumers

• Decomposers eat remains and wastes of other organisms

Trophic Levels

• Steps in a food chain

Trophic Levels

• Primary producers get energy from sunlight– MOST of the energy they use– SOME of the energy moves into the atmosphere

as heat– 10% of the energy is stored in plant tissues• Only this energy is available to the next trophic level!

Trophic Levels

• Primary consumers get energy from primary producers– MOST of the energy they use– SOME of the energy moves into the atmosphere

as heat– 10% of the energy is stored in body tissues• Only this energy is available to the next trophic level!

Trophic Levels

• Secondary consumers get energy from primary consumers– MOST of the energy they use– SOME of the energy moves into the atmosphere

as heat– 10% of the energy is stored in body tissues• Only this energy is available to the next trophic level!

Trophic Levels

• Tertiary consumers get energy from secondary consumers

10% Rule

• Only 10 percent of the energy in one trophic level is transferred to the next trophic level– If we start with 1000 calories of grass, how many

calories will make it into the rabbit?– How many calories will be transferred to the fox?– How many calories will be transferred to the wolf?

Energy Pyramid• It takes a large number

of producers to support a small population of primary consumers

• It takes a large number of primary consumers to support a small population of secondary consumers

• Etc.

This is why primary producers are the most abundant organisms in ecosystems

• Let's check this out at Yellowstone right now!

Biomagnification

• Concentrations of toxins increase as you move up the food chain

Biomagnification

Trophic Cascades

• The effects of top predators on ecosystems• How Wolves Change Rivers

Kahoot!

• Let's test ourselves!

Exit ticket

• Using complete sentences, explain why only 10% of the energy in one trophic level gets transferred to the next trophic level in an energy pyramid.

• (Hint: Where does the rest of the energy go?)