A food chain with three trophic levels

• A food chain shows the transfer of energy from one organism to the next, starting with a producer
• The source of all energy in a food chain is?light energy from the Sun
• The arrows in a food chain show the?transfer of energy?from one trophic level to the next
• Energy is transferred from one organism to another by ingestion (eating)
• In the food chain above:

Food Webs

• A?food web?is a network of interconnected food chains
• Food webs are more realistic ways of showing connections between organisms within an ecosystem as?animals rarely exist on just one type of food source

A food web shows the interdependence of organisms

• Food webs give us a lot more information about the transfer of energy in an ecosystem
• They also show?interdependence?- how the change in one population can affect others within the food web
• For example, in the food web above, if the?population of earthworms decreased:
  • The population of?grass plants would increase?as there are now fewer species feeding off them
  • The populations of?frogs and mice would decrease significantly?as earthworms are their only food source
  • The population of?sparrows would decrease slightly?as they eat earthworms but also have another food source to rely on (caterpillars)

   

• Most of the changes in populations of animals and plants happen as a result of?human impact?- either by?overharvesting of food species?or by the?introduction of foreign species to a habitat
• Due to interdependence, these can have?long-lasting knock-on effects?to organisms throughout a food chain or web