Trophic Levels,

Energy transfer

and Pyramids

Vocabulary

Trophic Levels – is the position an

organism occupies in a food chain. It

refers to food or feeding.

Apex predator – top level predators with

few or no predators of their own.

Food Chain

Food Chains

The energy flow from one trophic level to the

other is know as a food chain

Producers are at the first TROPHIC LEVEL

Primary Consumers are the SECOND TROPHIC

LEVEL

Secondary consumers are at the THIRD

TROPHIC LEVEL

Trophic Levels (feeding levels)

3

2

1

Food Web

Most organisms eat more than JUST one organism

When more organisms are involved it is know as a FOOD WEB

Food webs are more complex and involve lots of organisms

Food Webs

Food webs show

ALTERNATIVE PATHWAYS

other possible pathways

through which an

organism can obtain

energy

Food webs

Trophic Level Producer, primary

consumer, secondary

consumer, tertiary

consumer?

Grass

Mouse

Grasshopper

Frog

Owl

Hawk

Trophic Level Producer, primary

consumer, secondary

consumer, tertiary

consumer

Grass 1st Producer

Mouse 2nd Primary consumer

Grasshopper 2nd Primary consumer

Frog 3rd Secondary

consumer

Owl 3rd and 4th Secondary and

tertiary consumer

Hawk 3rd Secondary

consumer

Transfer of EnergyWhen a lion eats a zebra, it does

not get all of the energy from the

zebra.

Energy lost is usually in form of heat

Energy lost from chain “link” to “link”

is significant!

from grass to sheep, loss is about

90%!

10% Original

Energy! 1% Original

Energy!

100% Energy

Available

HEAT

90%

HEAT

90%

Energy lost from one trophic level

(energy level) to the next level can be

represented by a pyramid

PRODUCERS

1 CONSUMERS

2 CONSUMERS

3

CONSUMERS

4⁰CONSUMERS

Each level above only gets 10% of the energy from below

Ex: 10,000 J of producers (plants) only give 10% of energy to primary consumers

1,000 J to primary consumers (snails, minnows, dragonflies)

100 J to secondary consumers (small fish)

10 J to tertiary consumers (big fish)

1 J to quaternary consumers (fish hawk)

ENERGY PYRAMID

10,000 J

1,000 J

100 J

10 J

1 J

Energy Pyramid

Three hundred trout are needed to

support one man for a year. The trout, in

turn, must consume 90,000 frogs, that

must consume 27 million grasshoppers

that live off of 1,000 tons of grass. -- G. Tyler Miller, Jr., American Chemist

(1971)

Usually no more than 5 trophic

levels since 6th level would have

very little energy to keep it alive

Ecological Pyramid

• Which level has the most energy?

• Which level has the most organisms?

• Which level has the least organisms?

• Which level has the least energy?

Pyramid of Numbers

• Shows the numbers of individual organisms at each trophic level in an ecosystem.

tertiary

consumers

secondary

consumers

primary

consumers

producers

5

5000

500,000

5,000,0005,000,000producers

• A vast number of producers are required to support even a few

top level consumers.

Biomass pyramid • Biomass is a measure of the total dry mass of

organisms in a given area.

tertiary

consumers

secondary

consumers

primary

consumers

producers

75 g/m2

150g/m2

675g/m2

2000g/m2producers 2000g/m2