Food Webs and Food Chains

Ecology

Objectives

  • Identify different types of feeding relationships
  • Define food chain and food web
  • Identify organisms at different feeding levels
  • Construct a food chain
  • Identify food chains with at least 4 trophic levels from food webs

Feeding Relationships

  • Producers:

    • Make their own food (autotrophs).
    • Trap energy from the sun.
    • Make food through photosynthesis.

  • Examples of Producers:

    • Seaweed
    • Cyanobacteria
    • Phytoplankton
    • Plants

Feeding Relationships

  • Consumers:
    • Obtain food from other organisms (heterotrophs).
    • Categories:
      • Herbivores
      • Carnivores
      • Omnivores
    • Decomposers

Feeding Relationships

  • Herbivores:
    • Eat plants.

Feeding Relationships

  • Carnivores:
    • Eat meat.
      • Predators are a type of carnivore; they hunt prey animals for food.
    • Scavengers feed on carrion (dead animals).

Feeding Relationships

  • Omnivores:
    • Eat both plants and animals.

Feeding Relationships

  • Decomposers:
    • Break down complex compounds of dead and decaying plants and animals into simpler molecules that can be absorbed.

Food Chain

  • A simple diagram that shows how nutrients and energy flow from one organism to another.
  • Example:
    • Algae and floating plants → Aquatic crustaceans → Fish → Raccoons

Trophic Levels

  • Each link in a food chain is known as a trophic level.
  • Trophic levels represent a feeding step in the transfer of energy and matter in an ecosystem.

Trophic Levels

LevelType
1Producer
2Primary consumer
3Secondary consumer
4Tertiary consumer

Trophic Levels

  • Producers: Autotrophs
  • Primary consumers: Herbivores
  • Secondary consumers: Small carnivores
  • Tertiary consumers: Top carnivores

Food Web

  • Shows all possible feeding relationships in a community at each trophic level.
  • Represents a network of interconnected food chains.

Terrestrial Food Web

  • Examples:
    • Grasses, Grains, Carrots → Grasshoppers, Mice, Rabbits → Birds, Owls, Foxes

Aquatic Food Web

  • Examples:
    • Marsh Vegetation (sedges, grasses, bull rushes, algae, etc.) → Mosquito, Grasshopper, Rat, Vole, Snails → Herring, Salmon, Snow Geese → Bald Eagle, Harbour Seal, Marsh Hawk, Killer Whale