3.2 - How Do Organisms Get The Energy They Need?

• • Organisms that can change inorganic materials into chemical energy (food) by themselves are called Autotrophs
  • Ex: photoautotroph (producer) and chemoautotrophs (bacteria)
• • Organisms that rely on OTHER organisms for their chemical energy (food) are called heterotrophs
  • Ex: Humans
• • There are four kinds of consumers: herbivores, carnivores, omnivores, and detritivores
• • Herbivores -> eat only plants
  • Ex: deer, cow, giraffe, rabbit
• • Carnivore -> eats animals
  • Ex: wolf, shark, & tiger
• • Omnivore -> eats both plants and animals
  • Ex: squirrel, black bear, humans
• • Detrivore -> eats DEAD plants and animals
  • Ex: crayfish & hyena
• • Decomposers break down and absorb nutrients that are stored in dead organisms
  • Ex: fungus & bacteria
• Food Chain

  • We look at feeding relationships in a food chain
  • Each step in a food chain is called a trophic level
  • The first level is always producers/autotrophs
  • All other levels are made up of consumers/heterotrophs
  • The flow of energy in a food chain is always ONE WAY
  • Arrows move in the direction that energy is getting passed on to the organism in the food chain
• Food Web: interconnecting food chains in an ecosystem - it shows all possible feeding relationships in an ecosystem

  • All organisms are connected to decomposers -> when organisms die, their stored energy is passed on to decomposers when they absorb the decaying organisms
• Energy Pyramid: another way to show how food energy moves through an ecosystem AND the amount of food energy available to each trophic level

  • The 10% Rule:
  • The energy available to the higher trophic levels DECREASES in an ecosystem
  • Most of the energy they eat is used by the organisms to live for metabolism, waste & heat! Each level gets smaller