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Q.What is ecosystem? Discuss its different components with specific example of pond as an ecosystem. OR Describe various causes of loss of biodiversity.

Punjab PsebPSEB Punjab Class 12 Board 2018Subjective· 6mImportance★★★★★
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An ecosystem is a self-sustaining functional unit combining living organisms and their non-living environment, with a pond illustrating all its components — abiotic factors, producers, consumers, and decomposers.

What is an ecosystem?

An ecosystem is a functional unit of nature in which living organisms (biotic components) interact among themselves and with their surrounding physical environment (abiotic components), involving a continuous exchange of matter and flow of energy. Ecosystems can be natural (forest, pond) or man-made (crop field, aquarium), and vary in size.

Components of an ecosystem, illustrated with a pond as an example:

1. Abiotic components — the non-living physical and chemical factors:

  • Climatic factors: sunlight (light penetration), temperature of water.
  • Inorganic and organic substances: water itself, dissolved oxygen and CO2, dissolved nutrients/minerals (nitrates, phosphates), and organic matter/humus in the pond mud.

2. Biotic components — the living organisms, categorised by their functional role:

  • Producers (autotrophs): Phytoplankton (algae), and rooted/floating hydrophytes such as Hydrilla, Chara, water hyacinth — they photosynthesise and form the base of the pond's food chain.
  • Consumers (heterotrophs):
    • Primary consumers (herbivores): zooplankton and small herbivorous insects/larvae that feed on phytoplankton.
    • Secondary consumers (carnivores): small fish and insects that feed on the zooplankton.
    • Tertiary consumers: larger carnivorous fish, and birds like herons that feed on smaller fish, at the top of the food chain. …

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