CBSE – 10th Standard Science

Class 10 Chapter 15 – Our Environment


  •  Substances that are broken down by biological processes are said to be biodegradable
  • Non-biodegradable substances may be inert and simply persist in the environment for a long time or may harm the various members of the eco-system.



  • An ecosystem consists of biotic components comprising living organisms and abiotic components comprising.
  • All green plants and certain blue green algae which can produce food by photosynthesis are called the producers.
  • The organisms which consume the food produced, either directly from producers or indirectly by feeding on other consumers are the consumers.
  • Consumers can be classed variously as herbivores, carnivores, omnivores and parasites.


  • Decomposers break-down the complex organic substances into simple inorganic substances that go into the soil and are used up once more by the plants.
  • Series of organisms feeding on one another or organisms taking part at various biotic levels form a food chain.
  • Each step or level of the food chain forms a trophic level.
  • The autotrophs or the producers are at the first trophic level.
  • Autotrophs fix up the solar energy and make it available for heterotrophs or the consumers.
  • The herbivores or the primary consumers come at the second trophic level.
  • Small carnivores or the secondary consumers are at the third trophic level.
  • Larger carnivores or the tertiary consumers form the fourth trophic level.
  • The food we eat acts as a fuel to provide us energy to do work.
  • The interactions among various components of the environment, involves flow of energy from one component of the system to another.
  • The autotrophs capture the energy present in sunlight and convert it into chemical energy. This energy supports all the activities of the living world.
  • From autotrophs, the energy goes to the heterotrophs and decomposers.
  • The green plants in a terrestrial ecosystem capture about 1% of the energy of sunlight that falls
  • On their leaves and convert it into food energy.
  • Since so little energy is available for the next level of consumers, food chains generally consist of only three or four steps.
  • The loss of energy at each step is so great that very little usable energy remains after four trophic levels.
  • There are generally a greater number of individuals at the lower trophic levels of an ecosystem, the greatest number is of the producers.
  • So instead of a straight line food chain, the relationship can be shown as a series of branching lines called a food web.
  • The flow of energy is
  • As it moves progressively through the various trophic levels it is no longer available to the previous level.


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