Biology,  environmental science


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Several communities of organisms live together and interact with each other as well as with their physical environment as an ecological unit. We call it an ecosystem. The term ‘ecosystem’ was coined by A.G. Tansley in 1935. An ecosystem is a functional unit of nature encompassing complex interaction between its biotic (living) and abiotic (non-living) components. For example- a pond is a good example of the ecosystem.

Components of an ecosystem

Components of the ecosystem: They are broadly grouped into:-
(a) Abiotic and (b) Biotic components

A) Abiotic components (Nonliving):

The abiotic component can be grouped into the following three categories:-

  1. Physical factors: Sunlight, temperature, rainfall, humidity and pressure. They sustain and limit the growth of organisms in an ecosystem.
  2. Inorganic substances: Carbon dioxide, nitrogen, oxygen, phosphorus, sulphur, water, rock, soil and other minerals.
  3. Organic compounds: Carbohydrates, proteins, lipids and humic substances. They are the building blocks of living systems and therefore, make a link between the biotic and abiotic components.

B) Biotic components (Living)

  1. Producers: The green plants manufacture food for the entire ecosystem through the process of photosynthesis. Green plants are called autotrophs, as they absorb water and nutrients from the soil, carbon dioxide from the air, and capture solar energy for this process.
  2. Consumers: They are called heterotrophs and they consume food synthesized by the autotrophs. Based on food preferences they can be grouped into three broad categories. Herbivores (e.g. cow, deer and rabbit etc.) feed directly on plants, carnivores are animals which eat other animals (eg. lion, cat, dog etc.) and omnivores organisms feeding upon both plants and animals e.g. human, pigs and sparrow.)
  3. Decomposers: Also called saprotrophs. These are mostly bacteria and fungi that feed on dead decomposed and the dead organic matter of plants and animals by secreting enzymes outside their body on the decaying matter. They play a very important role in the recycling of nutrients. They are also called detrivores or detritus feeders.

Functions of ecosystem

Ecosystems are a complex dynamic system. They perform certain functions. These are:-

  1. Energy flow through the food chain
  2. Nutrient cycling (biogeochemical cycles)
  3. Ecological succession or ecosystem development
  4. Homeostasis (or cybernetic) or feedback control mechanisms Ponds, lakes, meadows, marshlands, grasslands, deserts and forests are examples of the natural ecosystem. Many of you have seen an aquarium; a garden or a lawn etc. in your neighbourhood. These are the man-made ecosystem.

Types of ecosystems

Ecosystems are classified as follows:
(i) Natural ecosystems (ii) Man-made ecosystems

  1. Natural ecosystems
    (a) Totally dependent on solar radiation e.g. forests, grasslands, oceans, lakes, rivers and deserts. They provide food, fuel, fodder and medicines.
    (b) Ecosystems are dependent on solar radiation and energy subsidies (alternative sources) such as wind, rain and tides. e.g tropical rain forests, tidal estuaries and coral reefs.
  2. Man-made ecosystems
    (a) Dependent on solar energy-e.g. Agricultural fields and aquaculture ponds.
    (b) Dependent on fossil fuel e.g. urban and industrial ecosystems.
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