Where energy comes from
Almost all energy in an ecosystem begins with the Sun. Green plants capture sunlight and use it to make food through photosynthesis. Because they produce food, plants are called producers. This energy then flows to other organisms when they feed.
Key idea
A food chain shows how energy flows from one organism to the next. The arrow always points in the direction the energy flows: grass → grasshopper → frog → snake. Each step is called a trophic level.
Producers and consumers
Organisms that eat other organisms are called consumers.
- Herbivores eat plants only (for example, a grasshopper).
- Carnivores eat other animals (for example, a snake).
- Omnivores eat both plants and animals.
When plants and animals die, decomposers such as bacteria and fungi break them down and return nutrients to the soil.
Food webs
In nature, animals usually eat more than one type of food. When many food chains link together, they form a food web. A food web gives a more complete picture of feeding relationships in an ecosystem.
Example
A hawk may eat both mice and small birds, so it belongs to two different food chains at once. Together these chains make a food web.
Remember
- The Sun is the main source of energy.
- Producers → herbivores → carnivores in a food chain.
- Arrows show the direction energy flows.