Lesson 3: Energy in Ecosystems
How does energy move in ecosystems?
 Matter cycles through an ecosystem
 Energy flows through an ecosystem
 Energy can change form as it moves through an ecosystem, but
the total amount of energy stays the same. This rule is called the
Law of Conservation of Energy.
Organisms that make their own food are producers
Photosynthesis- uses light energy to make food and oxygen from
carbon dioxide and water
Chemosynthesis- the process of making food energy using chemical
energy instead of light energy
Consumers obtain energy by eating other organisms.
 Herbivore- eats only plants
 Carnivores-animals that eat other animals
 Omnivores-eat producers and other consumers
Consumers called detritivores eat dead organisms.
Decomposers- another name for bacteria and mushrooms
 Decomposers help cycle nutrients through ecosystems
Modeling Energy in Ecosystems
 As energy changes from one organism to another in an ecosystem,
some stored chemical energy changes to thermal energy.
 A food chain is a model that shows how energy flows in an
ecosystem through feeding relationships
Food Webs
-A food web is when you overlap the food chains in an
ecosystem
-In a food chain and a food web, arrows show the movement of
energy
Energy Pyramids
An Energy Pyramid shows the amount of energy available in each step of
a food chain.
The steps of this energy model are called trophic levels
 the bottom layer of an energy pyramid contains producers
 the middle layer of an energy pyramid contains consumers that eat
producers
 the top layer of an energy in one step of an energy pyramid
contains consumers that eat other consumers
Only about 10 percent of the energy in one step of an energy pyramid
transfers to the next higher step.