In Depth Notes on Food Webs and Energy Flow

Food Webs

Energy Flow in Ecosystems

• Energy in ecosystems begins with the Sun, providing radiant energy.
• Autotrophs (Producers): Organisms that use sunlight to create their own energy.
  • Convert radiant energy into glucose (chemical energy) through photosynthesis.
  • Examples include:
  • Grass
  • Trees
  • Algae
  • Phytoplankton
• Some bacteria use chemosynthesis at hydrothermal vents, showcasing alternative energy creation.
• Heterotrophs (Consumers): Organisms that must consume other organisms to obtain energy.
  • Convert glucose from producers into ATP energy through cellular respiration.
  • Include: scavengers, decomposers.

Types of Organisms in Food Chains/Webs

• Producers:
  • Serve as the beginning of every food chain/web.
• Consumers:
  • Herbivore: Only consumes producers (plants).
  • Carnivore: Only consumes other consumers.
  • Omnivore: Consumes both producers and other consumers.
• Decomposers:
  • Break down decayed organic material into simple nutrients for producers.
  • Include bacteria, mushrooms, earthworms.
• Scavengers:
  • Consume decayed organic material, helping recycle nutrients (e.g., hyenas, vultures, dung beetles).

Food Chains and Trophic Levels

• Food Chain:
  • Represents energy transfer between organisms, starting with a producer.
  • Each organism in a food chain represents a different trophic level.
  • Arrows indicate direction of energy transfer.
• Trophic Levels:
  • Levels of organisms with the same feeding position in an ecosystem.
  • Producers: Create own energy.
  • Primary Consumers: Herbivores consuming producers.
• Energy Loss:
  • Energy in living organisms is termed biomass.
  • Organisms lose energy as heat while performing life processes.
  • 10% Rule: Only 10% of energy is transferred to the next trophic level, explaining fewer organisms at higher levels.

Food Webs

• Food Web:
  • Networks of interconnected food chains in an ecosystem.
  • Some organisms can occupy multiple trophic levels (e.g., a sparrow may be a primary and secondary consumer).

Symbiotic Relationships

• Symbiosis: A relationship between two organisms of different species living together.
  • Types include:
  • Mutualism: Both organisms benefit.
    • Examples: Bees and flowers, oxbirds and antelopes.
  • Commensalism: One organism benefits; the other is unaffected.
    • Examples: Barnacles on whales, birds living in tree holes.
  • Parasitism: One organism benefits at the expense of another.
    • Examples: Ticks on animals, mistletoe on trees.
• Other Relationships:
  • Predation: One organism eats another (e.g., owl and sparrow).
  • Competition: Multiple organisms compete for the same limited resources (food, habitat).
  • Can occur within the same species or different species (e.g., sea sponges vs. coral for nutrients).
• Not the same as parasitism.