18.2

All living things need energy to survive Everything we do requires energy Organisms are divided into three groups based on how they get their energy

Producers are organisms that use sunlight to make food. Mainly plants, but some bacteria can produce their own food. *Examples: grass, trees, algae

Consumers are any organisms that eat other organisms for energy There are three types of consumers Herbivores- eats only plants (cows, prairie dog) Carnivores- eat only meat (coyote, hawk, owl) Omnivores- eat both plants and animals (humans, mouse, rats)

Decomposers are organisms that get their energy from breaking down dead organisms They are the world’s natural recyclers Example: bacteria, maggots, flies

Diagram that shows the energy flow from one organism to the other. Use the following animals to build a food chain in your notes. Show where each animal will get their energy from. wolf bisongrass Grass  Bison  Wolf

Since animals eat more than one thing a food web is used to show the feeding relationship between organisms in an ecosystem. **Arrows go from the “food” to the consumer to show the transfer of energy**

As we move from producers to consumers the population decreases. Grass uses the energy from the sun to make food. 10% of the sun’s energy is stored in that grass. When a cow eats that grass it uses most of the energy from the grass up and stores 10 % in its tissue. When a cow is eaten by a human, the human uses most of the energy up and saves 10% in its tissue. There must be more grass than cows and more cows than humans for us to survive. Therefore less energy is available at the upper sections of the pyramid, because only stored energy is passed at 10%.