Energy Flow in Ecosystems

Chapter 2 Section 1 (pages 42-47)

Energy Roles

• Producer: an organism that can make its own food– Sunlight is the main energy source of life on Earth– Producers use the process of photosynthesis to

turn light energy into carbon dioxide and water into food molecules

• Examples: plants, algae, bacteria

Energy Roles

• Consumer – an organism that obtains energy from feeding on other organisms– Herbivores: obtain energy by eating only plants– Carnivores: obtain energy by eating only animals• Scavenger – carnivore that feeds on the bodies of dead

organisms– Omnivores: obtain energy by eating BOTH plants

and animals

Energy Roles

• Decomposers – break down wastes and dead organisms and return the raw materials to the ecosystem

ENERGY PATHS3 ways to

illustrate energy flow

1. Food Chain: Single path

2. Food Web: many paths 3. Food Pyramid

B. Food Chain—series of steps in which organisms transfer energy by eating and being eaten

1. Arrows go in the direction of how energy is transferred

2. Start with producer and end with top consumeror carnivore

Ex: grass cricket frog raccoon

C. Food Web—network of food chains within an ecosystem

Which of the organisms above is the producer?

Which of the organisms above is the top consumer?

Hawks

Weasels Raccoons

Mice

Grass

GrassHawks

FOOD CHAINS AND WEBS Practice! Draw a food

chain that includes the following organisms: grasshopper mouse grass owl

Now label the organisms as producers, consumers (which type?), or decomposers

FOOD CHAINS AND WEBS - ANSWER Practice! Draw a food

chain that includes the following organisms: grasshopper mouse grass owl

Now label the organisms as producers, consumers (which type?), or decomposers PRODUCER

CONSUMER(HERBIVORE)

CONSUMER(CARNIVORE)

CONSUMER(CARNIVORE)

FOOD CHAINS/WEBS & ENERGY PYRAMIDS• Food chains/webs can be

written as a pyramid:

– Producers form the base of the pyramid

Consumers form the upper layers

1. Level 1—Producers (autotrophs)

2. Level 2—Primary Consumers (herbivores)

3. Level 3—Secondary Consumers (carnivores or omnivores)

4. Level 4—Tertiary Consumers (carnivore—usually top carnivore)

Trophic Levels—each step in a food chain or food web

ENERGY PYRAMIDS

• A level of the energy pyramid is called a TROPHIC LEVEL

• Each trophic level represents the energy for those organisms

Top Consumer

Energy stored by Secondary Consumers

Energy stored byPrimary Consumers

ENERGY STORED BY PRODUCERS

The energy pyramid shows energy flow in an ecosystem:

Trophic Level Example

Level 4: Lion

Level 3: Wolf

Level 2: Rabbit, Deer

Level 1: Plants