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Revise Science Our Environment Notes Class 10 for better understandig of the concepts.

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Our Environment

  • Everything which surrounds us is environment.
  • Simply, the physical, chemical and biological conditions of the region in which an organism lives is called its Environment.
  • Our environment includes both living (biotic) as well as non-living (abiotic components)
  • Some of the man-made substance present in our environment is not acted upon by bacteria or saprophytes. They are acted upon by physical processes like heat and pressure.
  • Substances that are broken down by biological processes are said to be biodegradable.
  • On the other hand, substances that are not broken down in this manner are non-biodegradable.



  • The interaction and dependency of biotic and abiotic components on each other forms an ecosystem.
  • All organisms such as plants, animals, micro-organisms and human beings as well as the physical surroundings interact with each other and maintain a balance in nature.
  • An ecosystem contains biotic components comprising living organisms and abiotic components comprising physical factors like temperature, rainfall, wind, soil and minerals in our environment.
  • Natural ecosystem includes forest, ponds lakes while artificial or man-made ecosystem includes gardens, crop fields, aquarium etc.

Biotic components are further classified as:

  • Producers: The component of ecosystem which produces their own food (photosynthesis) are said to be producers. All green plants and blue-green algae are producers.
  • Consumers: The component of ecosystem in our environment which either directly or indirectly on producers for their food. All animals are consumers.

Classification of consumers:

classification of consumers

Consumers are further classified into different categories:

  1. Herbivores: The animal who eats grass or plants are herbivores. Example: goat, deer etc.
  2. Carnivores: Those animals which eat meat or flash of other animals are carnivores. Example: Tiger, lion, crocodile etc.
  3. Omnivores: Those animals which eat both plants, as well as animals, are called omnivores. Example: Human
  4. Parasites: Those animals which reside on the body of host and takes nutrition from it are parasites. Example: Lice, Cascuta etc.
  5. Decomposers: Those organisms which decompose the dead plants and animals are decomposers. Example: Bacteria, Fungi etc.

Food Chain:

food chain

  • The series of organisms dependent on others for their food are said to be food chain.
    As example: Grass – Deer – Lion
  • Each step or level of the food chain forms a trophic level where transfer of energy takes place.
  • Plants or autotrophs are at 1st trophic level, herbivores are at 2nd trophic level and the small carnivores are at 3rd tropic level and larger carnivores at 4th trophic levels.

Flow of Energy between trophic levels:

trophic levels

  • 1% of the total energy of the sun is utilized by the plants to convert into food energy.
  • 10 per cent law: Only the 10% of total energy is transferred to the next trophic level, rest 90% of the energy is used by the present trophic level for the life processes (such as digestion, growth, reproduction etc.)
  • The flow of energy is unidirectional.
  • Food chain contains only 3 to 4 trophic levels due to this gradual decrease of transference of energy from one trophic level to other. 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, so producers are present in large numbers.

Food Web:

food web

  • Each organism is generally eaten by two or more other kinds of organisms which in turn are eaten by several other organisms. So complexity of food chains varies greatly.
  • We see that instead of a straight line food chain, the relationship can be shown as a series of branching lines, this arrangement is called food web.

Environmental problems:

We always see around us that a little change in environmental conditions affects us badly. Our activities also affects our environment in the same way. Humans are integral part of the environment and occupy the top trophic level. Human activities lead to pollution, deforestation, green-house effect, ozone layer depletion etc.

Ozone layer:

  • When three atoms of oxygen combines together then it forms ozone (O­3). It is deadly poisonous gas.
  • However, at the top level of atmosphere ozone plays an important role. As it shields the earth’s surface from ultraviolet (UV) radiation from the sun.
  • UV radiation is highly dangerous radiation which causes skin cancer in human beings and also affect other organisms too.
  • At upper levels when high energy UV rays falls on oxygen molecules it splits apart the oxygen molecules into free oxygen atoms and these free oxygen atoms combine with oxygen molecule to form ozone.
  • The depletion of ozone layer is due to excessive use of synthetic chemicals like chlorofluorocarbons (CFCs) which are used as refrigerants and in fire extinguishers.

Garbage disposal:

  • As we have modernized, our lifestyle has improved. It resulted in larger amount of waste generation.
  • Everywhere in our environment we see that there is wide accumulation of garbage.

Methods of garbage disposal:

  • Biodegradable waste can be used in bio gas plants to produce biogas as well as manure.
  • The dirty water of drains must be cleaned in sewage treatment plant before adding it to rivers.
  • In every city, there is a low lying area which can be filled with the garbage and made compact for land use.
  • Some vegetable waste and organic waste is filled in a compost pit and covered with a layer of soil. Within 3 to 4 months these organic waste turns to manure which is useful for agricultural purpose.

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