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 the mollusk which is consumed by  the white perch would be an example of moving up a trophic level. Producers which use photosynthesis to create their energy are a large source of energy in an ecosystem. Plants and algae are examples of producers.

As consumers eat these producers, carbon bonds are broken and energy is released and this energy is transferred from one trophic level to another. 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.

energy pyramid

For example, if you start with 1000 Joules and a grasshopper eats a plant only 10 Joules will be transferred, and if a bird eats the insect only 1 Joule will be transferred. Notice that as you move up the energy pyramid, roughly only 10% of the energy is transferred to the next trophic level. This explains why there is a smaller number of organisms as you move up the energy pyramid.

In an ecosystem, organisms obtain energy through their diet, occupying various positions in the food chain. These positions are known as trophic levels. Consumers are organisms that obtain their energy by consuming other organisms. Based on their position in the food chain, consumers can be classified into the following types:

Producers:

  • Producers are organisms that can produce their own food from inorganic substances, utilizing energy from the sun through the process of photosynthesis.
  • Examples include plants and algae.


Primary Consumers (Herbivores):

  • Primary consumers are organisms that feed directly on producers.
  • They are typically herbivores, consuming plants and algae.
  • Examples include grasshoppers, deer, and rabbits.

Secondary Consumers (Carnivores):

  • Secondary consumers are organisms that feed on primary consumers.
  • They are typically carnivores, consuming animals that feed on plants.
  • Examples include snakes, spiders, and birds of prey.


Tertiary Consumers (Top Carnivores):

  • Tertiary consumers are organisms that feed on secondary consumers.
  • They are typically top carnivores, occupying the highest trophic level in the food chain.
  • Examples include lions, tigers, and sharks.


Quaternary Consumers:

  • Quaternary consumers are a category sometimes used to describe organisms that feed on tertiary consumers.
  • They are typically apex predators, occupying the highest trophic level in the food chain.
  • Examples include polar bears and orcas.

 

energy pyramid losing energy as heat

Where does this energy go?
Most of the energy is lost as heat. 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.

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.

You may enjoy these videos on Energy flow in an ecosystem.