Energy flow in an Ecosystem Trophic Levels

Energy Flow in an Ecosystem

All living things need energy. Some biotic factors get their energy from the sun, while some eat other biotic factors. As a result energy is always flowing in ecosystems. This flow of energy can be represented with food chains and food webs. For most ecosystems, the ultimate energy source is the sun. As you move from one organism to another you move up trophic levels.  For example, moving from a plant to an animal would be an example of moving up a trophic level.


Let’s take a look at trophic levels.


Producers are organisms that use photosynthesis to create their energy from sunlight. They are the first trophic level in the food chain. Plants and algae are examples of producers.


Consumers are organisms that cannot produce their energy and must eat other organisms to obtain energy. Consumers are divided into different trophic levels based on their position in the food chain:

  • Primary Consumers: These are organisms that eat producers. They are the second trophic level in the food chain. Grasshoppers and rabbits are examples of primary consumers.
  • Secondary Consumers: These are organisms that eat primary consumers. They are the third trophic level in the food chain. Snakes and birds are examples of secondary consumers.
  • Tertiary Consumers: These are organisms that eat secondary consumers. They are the fourth trophic level in the food chain. Wolves and bears are examples of tertiary consumers.
trophic levels

As you move from one trophic level to another you lose roughly 90 percent of the energy.

This is known as the 10 percent rule.

For example, if you start with 1000 Joules and a grasshopper eats the plants only 10 Joules will be transferred, and if a bird eats the insect only 1 Joule will be transferred.

Where does this energy go? 

 The energy flow in an ecosystem follows the laws of thermodynamics.

The first law states that energy cannot be created or destroyed in an isolated system however it can be converted from one form to another.

The second law states that this energy conversion is never completely efficient.

As a result, most energy is lost as heat.