Our enviromentMade by :- Vivek,Roopesh,Allen,Sheetal,PriyankaClass :- X ‘A’

• The physical and biological world where we live is called our environment.

• The environment includes our physical surroundings like air , water bodies , soil (land)and all the organisms such as plants , animals, human beings and micro-organism like bacteria and fungi (called decomposers).

Environment

• Those wastes materials which can be broken down to harmless or non-poisonous substances in nature in the due course of time by the action of micro-organism like certain bacteria, are called biodegradable wastes.

• A biodegradable waste decays(decomposes) naturally and becomes harmless after some times.

• Examples :- cattle dung , compost , sewage , paper , cloth , wood etc.

Biodegradable wastes

• The materials which cannot be broken down into non-poisonous or harmless substances in nature are called non-biodegradable wastes.

• Examples :-D.D.T. (Dichloro Diphenyl Trichloroethane) , plastics , polythene bags , synthetic fibres , radioactive wastes etc.

Non-biodegradable wastes

• It is the structural and functional unit of biosphere, comprising of all the biotic and abiotic components of the environment.

• Thus, an ecosystem is a self sustaining system where energy and matter are exchanged between living and non-living components.

Ecosystem

• Natural ecosystem :- The natural ecosystem is terrestrial as well as aquatic. For example, forests , grasslands , deserts , ponds , lakes etc.

Types of ecosystem

• Artificial ecosystem :- are made by human beings.

• For example:- crop field , gardens , parks , aquarium, etc.

• Anything which we eat to live is called food.

• The food can be transferred from one organism to the other through food chain. Energy is transferred by the process of one organism consuming the other.

• Example of a simple food chain

• Plants Worms Birds Cat

Food chain

• The various of steps in food chain at which the transfer of food (or energy) takes place are called trophic level.

Trophic levels

• Producers occupy the first tropic level.

• Producers are the organisms which can prepare their own food from simple inorganic substances like carbon dioxide and water by using sunlight energy in the presence of chlorophyll.

• The examples of producers are Green plants and certain blue-green algae.

• This are called autotrophs.

• Primary consumers (herbivores) occupy the second level in the food chain. This organisms feed upon plants.

• Some examples of herbivores are cow, goat, sheep , camel, elephant, etc.

• Carnivores ( that feed upon herbivores ) constitute the third trophic level. They are the secondary consumers.

• Some examples of carnivores are fox, jackal, bear, frog, etc.

• Large carnivores or top carnivores (which feed upon small carnivores), constitute the fourth tropic level. They are the tertiary consumers.

• Some examples of tertiary consumers are lion, tiger, hawk, etc.

• The 10 per cent law which was given by Raymond lindeman in the year 1942, is one of the most useful generalisation about the magnitude of loss of energy in food chains.

10 per cent law

• According to 10 per cent law, only 10 per cent of the energy entering a particular trophic level of organisms is available for transfer to the next higher trophic level.

• The energy available at each successive trophic level is 10 per cent of the previous level.

Chlorofluorocarbons (CFCs)• This compound’s highly stability to temperatures makes

them suitable for a variety of uses such as in aerosols and refrigerators coolants. They are often known as freons.

• CFCs are stable. They do not degrade easily and rise to the stratosphere, where they are broken down by UV radiation resulting attack on the ozone molecules damaging the ozone layer.

• There are several reasons for the depletion of ozone layer :-

• The foremost reason is the use of CFCs. The other factor responsible for the destruction is the pollutant nitrogen monoxide (NO).

• When this harmful chemicals like CFCs are released into the air it accumulates in the stratosphere and reacts with the ozone layer by forming a hole.

• Thus, the ozone layer becomes thinner and gets depleted allowing more UV rays to pass through the earth.

Depletion of ozone layer

Harms caused by the depletion of the ozone

layer

Skin cancer

Due to the depletion of ozone layer, ultraviolet rays causes ill effect which are globally bad and harmful.

• For example :- skin cancer , cataract and certain other problems to our immune system.

cataract