Food Chains and Food Webs
Energy Flow in Nature
Energy Roles
•An organism’s energy role in an ecosystem may be that of a producer, consumer, or decomposer.
Producers
•An organism that can make its own food is a producer.
•Autotroph•Source of all food in an
ecosystem.•Capture energy from
sunlight and stores it as food energy.
Consumers
• Consumers are heterotrophs, or living things that cannot make food for themselves.
• A food chain contains several kinds of consumers, each of which occupies a different trophic level.
• Herbivore, carnivores, omnivores
Consumer Tropic Levels
• Primary consumers eat producers (herbivores)
• Secondary consumers eat primary consumers (carnivores)
• Tertiary consumers eat secondary consumers (carnivores)
• Scavengers are carnivores that feed on the bodies of dead organisms.
Decomposers
•Help break down wastes and dead organisms and return the raw materials to the environment
•Bacteria and fungi
Food Chains•Series of events where one organism eats another and obtains energy.
•First organism in chain is the producer.
•The second organism is the consumer that eats the producer.
Plankton—Crab—Seal—Orca
This is only one possible chain in a marine ecosystem.
Come up with an example to fill in the blocks of a food chain in two different ecosytems.
Food Webs•Consists of many overlapping food chains in an ecosystem.
•Some organisms may play more than one role by changing consumer levels.
What happens in a food web if one or more of the
organisms disappear?
Which animals are carnivores and herbivores?
Energy Pyramids
•A diagram that shows the amount of energy that moves from one feeding level to another in a food web.
•Represented in a triangle with the most energy at the producer level.
Energy Loss and Use
•10% of energy transferred to next higher level.
•90% of energy is used by organisms’ life processes.
•Due to energy loss, ecosystem cannot support many feeding levels.
