Food and Energy in the Environment

Energy Roles

Organisms may be producers, consumers, or decomposers

These terms indicate how an organism obtains energy and how it interacts with the other living things in its community.

Producers

Means that they make their own food

Able to use a source of energy (sunlight) to turn simple raw materials (such as water and carbon dioxide) into food (like the sugar glucose).

Producers are the source of all the food in an ecosystem

Consumers

Organisms that cannot make their own food depend on producers for food and energy.

An organism that feeds directly or indirectly on producers is called a consumer.

Herbivores: eat only plants, such as rabbits

Carnivores: eat only meat, such as wolves

Omnivores: eat both plants and animals, such as humans

Scavengers: an animal that feeds on the bodies of dead animals, such as jackals, hyenas, and vultures

Decomposers

After living things die, organisms called decomposers use the dead matter as food.

Decomposers break down dead organisms into simpler substances.

Molds, mushrooms, and many kinds of bacteria are examples of decomposers

Essential to the ecosystem because they rid the environment of the bodies of dead plants and animals

They also return nutrients (compounds containing chemicals such as nitrogen, carbon, phosphorus, sulfur, and magnesium) to the environment, which are used by plants to make food

Food Chains & Food Webs

In general, food and energy in an ecosystem flow from the producers to the consumers in an ecosystem are represented by food chains and food webs.

Food chains represent a series of events in which food and energy are transferred from one organism in an ecosystem to another

Example: diatoms krill squid penguin killer whale

A food chain gives you a glimpse of the food and energy relationships in an ecosystem, but it does not give you the whole picture

– There are many organisms in an ecosystem and few of them eat only one kind of food

– There must be more than one food chain in an ecosystem

A food web consists of many overlapping food chains

Feeding Levels

A feeding level is the location of an organism along a food chain

Producers form the first feeding levelHerbivores form the second feeding

levelCarnivores form the third feeding

level

At each feeding level, organisms use the energy they obtain to digest their food, reproduce, move, grow, and carry out other life activities

This means there is less energy available to each level as you progress up the feeding levels

These levels form an energy pyramid