Food Webs and Ecosystem Relationships

Food Webs

Energy in Ecosystems

• All energy flow in ecosystems starts with the Sun (radiant energy) but is not included in food webs/chains.

• Autotrophs (Producers):

  • Convert radiant energy into glucose (chemical energy) via photosynthesis.
  • Examples: grass, trees, algae, phytoplankton.
  • Some bacteria at hydrothermal vents utilize chemosynthesis (another form of energy creation).

• Heterotrophs (Consumers):

  • Must consume other organisms for energy.
  • Converts producer glucose into ATP through cellular respiration (usable energy).
  • Types of consumers: scavengers and decomposers.

Trophic Levels & Energy Flow

• Food Chains:

  • Show how energy is transferred between organisms, starting with a producer.
  • Each organism occupies a different trophic level indicated by arrows showing energy flow direction.

• Trophic Levels:

  • Levels share the same feeding positions based on energy acquisition.
  • Examples:
  • Producers: Create their own energy.
  • Primary Consumers: Herbivores that consume plants.
  • Secondary Consumers: Carnivores that consume herbivores.

• Energy Loss:

  • Energy in organisms is referred to as biomass.
  • Energy loss occurs during life processes (metabolism, respiration), producing heat.
  • Only about 10% of energy from one trophic level is transferred to the next, explaining the larger number of organisms at lower levels.

Food Webs

• Food Webs:
  • Interconnected food chains within the same ecosystem.
  • Some organisms, such as omnivores, function at multiple trophic levels (e.g., sparrows as both primary and secondary consumers).

Symbiotic Relationships

• Symbiosis:

  • Interaction between two different species in an ecosystem.

• Types of Symbiotic Relationships:

  1. Mutualism:
  • Both organisms benefit.
  • Examples:
    • Bees collect pollen while pollinating flowers.
    • Oxbirds eat parasites on antelopes.
    • Algae on coral provide nutrients and receive protection.
  1. Commensalism:
  • One organism benefits, and the other is unaffected.
  • Examples:
    • Barnacles attach to whales.
    • Birds nesting in tree holes.
  1. Parasitism:
  • One organism benefits at the other's expense.
  • Examples:
    • Ticks feeding on animals.
    • Mistletoe extracting nutrients from trees.

Other Relationships

• Predation:

  • One organism (predator) eats another (prey).
  • Apex predators have no natural predators.
  • Example: Owls prey on sparrows.

• Competition:

  • Multiple organisms competing for limited resources (food, habitat).
  • Can occur within the same or different species.
  • Example: Sea sponges and corals competing for the same nutrients.

• Note: Competition is distinct from parasitism.