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Organisms and Populations

Organisms and Environment

  • Ecology deals with interactions among different organisms and their environment.

  • Organisms get adapted to their environment for their survival and reproduction.

  • The rotation of the earth about its axis brings about changes in the environment, leading to different seasons. This leads to the formation of various biomes such as desert, grassland, etc.

  • Life not only exists in favourable habitats, but also in harsh and extreme conditions.

  • The environment of an organism can be divided into:

    • Abiotic factors

    • Biotic factors

Abiotic Factors

  • Some of the major abiotic factors that interact with the organisms are:

    • Temperature − It is the most relevant abiotic factor since all organisms require an optimum temperature for their metabolism and other body functions. Depending upon their ability to tolerate temperature range, organisms are of two types- stenothermal (restricted to a narrow range of temperature) and eurythermal (can tolerate a wide range of temperature).

  • Water − Water also is a major influencing factor. Life on earth is impossible without water as it forms the major constituent of all living cells. In oceans where quantity of water is not a limitation, the quality of water becomes one. Depending upon the ability to tolerate salinity, organisms can be stenohaline (restricted to narrow range of salinity) and euryhaline (tolerant to wider range of salinity).

  • Soil − The nature and composition of soil differs from one place to another depending upon the climate, weathering process, and soil development method. The characteristic features such as soil composition, grain size, percolation, water holding capacity, etc. determine the native of the organisms it can support.

  • Light − The major source of light on earth is the Sun. Light is essential for plants to perform photosynthesis. Certain plants become adapted to perform photosynthesis under very low light since they are constantly overshadowed by tall trees. Many plants also depend on light for their flowering (photoperiodism). The availability of light on land is comparatively higher than that in water.


  • It is a group of similar individuals living in a geographical area, sharing similar resources, and capable of interbreeding.
  • Population has certain attributes, which individual organisms…

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