Energy Flow Pyramids and Trophic Levels

TROPHIC LEVELS

An organisms trophic (feeding) level is determined

by the organism’s source of energy

There are 3 main trophic levels in a food web.1. Autotrophs

2. Heterotrophs

3. Saprotrophs

1. AUTOTROPHS:

• Capture energy from the sun (photosynthetic) or inorganic molecules (chemosynthetic) and converts it into usable energy.

• Also known as (AKA) PRODUCERS– produces food (make energy storing

molecules),

• Eg. Plants, algae and some kinds of bacteria

2. HETEROTROPHS-• AKA CONSUMER

– obtains the energy to build their molecules by consuming plants or other organisms

Includes:

– primary,

– secondary,

– tertiary (etc.) consumers, and

3. SAPROTROPHS/DECOMPOSERS

• An organism that gets it’s energy by feeding off of dead or decaying organic matter

• 2 types:

Detritivores and Scavengers

SCAVANGERS

• Start the decomposition process by finding large quantities of dead material (like corpses) and breaking it down into smaller pieces.

– Eg. Hyenas, Crabs, Vultures.

DETRITIVORES

• Organisms that eat detritus, or dead organic matter.

• Finish the decomposition process by taking the leftovers from scavengers or waste from other organisms and breaking it down to the molecular level.

– Eg. Fungi, Bacteria, Earth Worms

How do you tell the difference between a Scavenger and Detritivore?• Scavengers tend to start the decomposition process by

turning large pieces of food into smaller one. Detritivoresfinish the process by breaking the smaller food into molecules that are recycled into the ecosystem.

• Scavengers are typically larger animals, while Detritvorestypically are smaller microorganisms or invertebrates (though fungi can get quite large).

• Scavengers typically have large ranges that they travel to find corpses. Detritivores typically stay in one general area and eat what ever waste, dead left overs come to them.

Energy Pyramid Model

• Organisms convert food (glucose) into energy.

• This energy is given off as heat which is lost to space.

• Energy is a one way path. It is not a cycle.

Energy Flow Models:

graphs which illustrate the trophic levels in a community.

Energy Pyramid Model

• An energy pyramid is a diagram that compares energy used by producers, primary consumers, and other trophic levels.

• As a rule each trophic level receives only 10% from the trophic level below.

• In other words each trophic level loses 90% heat to the atmosphere.

Student Task

• Study the food web and convert it into an energy pyramid model.

• The autotrophs in this food web start off with 123,000 kilojoules of energy and the decomposers are included on the outside of the pyramid.

• Also label the levels with the terms on paper

flowers, grasses (seeds, berries)

Marmot, Grouse, Butterfly, Deer, Chipmunk, Bear

Red-tailed hawk,Bear,

Hawk

ProducersAutotrophs

Primary ConsumerHeterotroph, Herbivore

Secondary ConsumerHeterotroph, Carnivore

Carnivore

123,000 kJ

12, 300 kJ

1,230 kJ

123 kJ

SaprotrophsMushrooms, earthworms

Decomposer, Detritivore

Pyramid of Biomass

• Biomass is the mass of organisms minus water.

• Biomass refers to the amount of carbon and other trace elements an organism’s body contains.

Student Task

• Study the food web below and convert it into a biomass pyramid model.

• The autotrophs (phytoplankton) in this food web start off with 5,693,112 Kg of biomass.

• Also label the levels with the terms found on your paper

Phytoplankton

cod, krill, zooplankton

Penguin, Leopard seal, squid, cod

Elephant Seal, Killer Whale

Autotrophs, producers

Primary consumer, herbivore, heterotroph

Secondary Consumer, Carnivore, heterotroph

Tertiary Consumer, Heterotroph, Carnivore

5,693,112 kg

569,311 kg

56,931 kg

5,693 kgWhale

Student Task

Pyramid of Numbers

Illustration of the number of organisms at each level

How can more people be supported on Earth when there is a limited supply of resources?

• It depends on what they are eating.

EXIT SLIP

Plant material eaten by caterpillar

100 kilocalories (kcal)

Feces

50 kcal

Growth

15 kcal

Cellular respiration

35 kcal

Explain this graphic- feel

free to draw it out.

In your answer, make

sure to tell me:

• How much energy did

the plant start with?

• How much energy will

go to the crow? Why?

• What will there be the

most of in this

ecosystem: plants,

caterpillars, or crows?

How do you know?