Understanding Food Webs

• Organisms in a Food Chain are dependent on others.
  • Example: Grass is eaten by rabbits which are hunted and eaten by foxes.
• Grass captures the energy from the sunlight to photosynthesise and make glucose.
• Glucose provides energy for the plant to grow.
• When a rabbit eats grass, the energy left in the grass is transferred to the rabbit.  The rabbit uses some of this energy to move and grow.
• When a fox eats a rabbit the remaining energy in the rabbit is transferred to the fox.

Changes in the number of one organism in a food chain can affect other organisms in the food chain. Here are some examples how:

• The number of plants in an ecosystem can be affected because of the amount of rain, sunlight, minerals as well as the space that is avaliable to grow.
• The number of animals can be affeccted by the amount of food, habitats, mates, water and disease.

Most animals eat many different things and are involved in many different food chains. These food chains can be put together in a Food Web, which shows how the food chains are connected. Food webs can sometimes be very complex!

In a food web, there are different rankings. These are listed below.

• Produces make their own food.
• Primary Consumers eat producers
• Secondary Consumers eat primary consumers
• Tertiary Consumers eat secondary consumers.

These rankings are called Trophic Levels. The trophic levels of an organism is the position it occupies in a food chains.

The arrows in a Food Web indicate the Direction of the Energy Flow.

• Food chain
• Food web
• Primary consumer
• Secondary consumer
• Tertiary consumer
• Trophic level