Food Chains & Food Webs | Biology for GCSE/IGCSE - Year 11 PDF Download

Food Chains

• A food chain demonstrates the transfer of energy from one organism to another, commencing with a producer.
• Light energy from the Sun serves as the fundamental energy source in a food chain.
• The directional arrows in a food chain exhibit the flow of energy from one trophic level to the next.
• Energy is conveyed from one organism to another through ingestion (consumption).
• In the depicted food chain:

Food Webs

• A food web, a complex network of interconnected food chains, represents a more realistic portrayal of how organisms in an ecosystem interact.
• Food webs illustrate the diverse connections between organisms, highlighting that animals seldom rely on a single food source.

The Significance of Food Webs

• Food webs exhibit the interdependence of organisms within an ecosystem, showcasing how various species rely on each other for sustenance.
• They offer valuable insights into energy transfer within ecosystems and demonstrate the concept of interdependence.
• For instance, a decrease in the earthworm population can trigger a cascade of effects:
  • The dwindling earthworm population leads to an increase in grass plants, as fewer organisms feed on them.
  • Frogs and mice, heavily reliant on earthworms as their primary food source, experience significant population declines.
  • Sparrows, while mildly impacted due to their varied diet including caterpillars, also witness a slight decrease in population.
  • Human activities, such as overharvesting or introducing alien species, can disrupt food webs, causing lasting repercussions across ecosystems.
• Most changes in animal and plant populations are a result of human activities: Human actions such as overharvesting food species or introducing non-native species can disrupt the natural balance of ecosystems, causing ripple effects throughout the food chain.
• Long-lasting consequences of human-induced changes on organisms in food chains: These alterations can have enduring impacts on various species within the ecosystem, potentially leading to imbalances that persist over extended periods.