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