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

– decomposers and detritivores

Saprotrophs

• AKA detritivores and decomposers

• An organism that feeds off of dead or decaying organic matter

• Examples:

– Fungus

– Vultures

DETRITIVORES

• Organisms that eat detritus, or dead organic matter.

– Eg. Earthworm, vulture, crab

DECOMPOSERS • A kind of detritivore

– Break down organic matter into simpler compounds.

• release essential nutrients back into the environment to

be recycled.

– Eg. Fungus

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

Red-tailed hawk, grizzly bear, Mushrooms and earthworms

Hawk

Producers autotrophs

Primary Consumer Heterotroph, herbivore

Secondary Consumer Heterotroph, Decomposer, detritivore, carnivore

Carnivore

123,000 kJ

12, 300 kJ

1,230 kJ

123 kJ

Saprotrophs Mushrooms, earthworms

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 in this food web start off with 5,693,112 Kg of biomass and the decomposers are included on the outside of the pyramid.

• 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 kg Whale

Mushrooms, earthworms

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.