How Ecosystems Work

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Detailed Summary

  • An ecosystem is a natural unit made up of living organisms (biotic) interacting with their non-living surroundings (abiotic). It is self-sustaining because energy flows through it and nutrients recycle within it.

Components of an Ecosystem

  • Biotic components (living):
    • Producers (autotrophs): Plants, algae, some bacteria. They capture sunlight and make food through photosynthesis.
    • Consumers (heterotrophs):
      • Primary consumers (herbivores) eat producers (e.g., grasshopper, cow).
      • Secondary consumers (carnivores) eat herbivores (e.g., frog, lizard).
      • Tertiary consumers (top carnivores) eat other carnivores (e.g., eagle, lion).
      • Omnivores eat both plants and animals (e.g., humans, bears).
    • Decomposers (saprotrophs): Bacteria, fungi—break down dead organisms, recycle nutrients.
  • Abiotic components (non-living): sunlight, air, water, soil, minerals, and temperature. These influence which organisms can survive in an ecosystem.

Food Chains

  • A food chain shows a direct line of “who eats whom.” Example: Grass → Grasshopper → Frog → Snake → Eagle
    • Always starts with a producer.
    • Energy decreases at each step (trophic level) because some is lost as heat.

Food Webs

  • Real ecosystems are more complex than a simple chain. Organisms often eat more than one type of food.
  • A food web is a network of interconnected food chains, showing stability in the ecosystem.

Flow of Energy

  • Energy enters ecosystems through sunlight.
  • Producers capture only a small fraction of it.
  • Energy passes from one trophic level to the next but reduces at each step (10% law).
  • Flow of energy is unidirectional (one-way), unlike nutrients which recycle.

Nutrient Cycling

  • Elements like carbon, nitrogen, phosphorus, oxygen, water move through cycles.
  • Producers absorb nutrients → consumers eat producers → decomposers return nutrients to soil/air.
  • This maintains balance.

Types of Ecosystems

  • Natural ecosystems: forests, grasslands, ponds, oceans, deserts.
  • Artificial ecosystems: aquariums, crop fields, gardens.
  • Oxygen, food, water.
  • Raw materials like timber, medicines, fibres.
  • Climate regulation & soil fertility.
  • Habitat for biodiversity.
  • Nutrient cycling & energy flow that sustain life.