Edexcel IGCSE Biology: Double Science 复习笔记 4.2.2 Food Webs

Edexcel IGCSE Biology: Double Science 复习笔记 4.2.2 Food Webs

Food Webs


  • 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




Food Web Definitions Table






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 on organisms throughout a food chain or web


Exam Tip

Questions about interdependence in food webs are common and easy to gain marks on if you answer them fully and correctly.Do not say an animal or plant would ‘die out’ as this is unlikely to happen – stick to using the words decrease or increase. If in doubt, always give your reason for the increase or decrease in population.