Food Chains and Food Webs

Food Chains and Food Webs

Food Chains

  • A food chain is a description of how energy and nutrients pass from one organism to another in an ecosystem.
  • It starts with a producer, usually a green plant or algae, which gains energy from the Sun.
  • The producer is eaten by a primary consumer, usually a herbivore, which is then eaten by a secondary consumer, typically a carnivore.
  • Each stage in this chain is known as a trophic level.
  • All food chains finish with a top predator such as a hawk or a fox, which is then broken down by decomposers once it dies.

Food Webs

  • In real ecosystems, the feeding relationships are often more complex than a simple food chain. These interconnected food chains form a food web.
  • A food web shows the various paths along which energy and nutrients can flow from one organism to another.
  • Organisms may have multiple predators and prey, and occupy multiple trophic levels in different food chains, adding complexity to the web.
  • The ultimate energy source for all food chains and food webs is the Sun.


  • Decomposers are organisms such as bacteria and fungi that break down dead plants and animals into simpler substances.
  • They play a crucial role in recycling nutrients within an ecosystem, returning the components of dead organisms back into the soil where they can be absorbed by plants for growth.
  • Even though decomposers do not directly get their energy from the Sun, they are indirectly dependent on solar energy, as they break down organisms within the food web which originally derived energy from the Sun.

Disruptions in Food Chains and Webs

  • Disruptions in a food chain or web, such as the removal of a key species, can have significant consequences for the entire ecosystem.
  • If a species is removed, its predators may starve and its prey may overpopulate, disrupting the balance of the ecosystem.
  • If a new species is introduced, it could become a competitor or predator, affecting the native species and overall biodiversity.
  • These factors highlight the importance of maintaining biodiversity and protecting endangered species to ensure the health and stability of ecosystems.