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• Biodegradable v/s  Non biodegradable substances :

• Ecosystem :  “The community in which living and nonliving things interacts and maintain balance in nature.”
• Types of ecosystem :
1. Artificial ecosystem : Manmade ecosystems e.g. gardens, crop fields, etc.
2. Natural ecosystem : Ecosystems that are produced naturally. E.g forest, lakes, ponds, etc.
• Components of ecosystems : All living and nonliving organisms  present in ecosystem.
• Biotic components of ecosystem :  Living organisms in ecosystems. E.g. e.g. plants, animals, microorganisms and human beings. They are classified as-
• Producers : Organisms prepare their own food by process of photosynthesis. E.g.  Plants, Blue-green algae.  
• Consumers : Organisms directly / indirectly dependent on producers. E.g. Human, birds, animals, aquatic organisms. They are further classified as :
1. Herbivorous : Organisms directly dependent on plants. E.g. Goat .
2. Carnivorous : Organisms which obtain food from other animals by eating them. E.g. Tiger.   
3. Omnivorous : Organisms that obtain food by eating plants or animals. E.g. Human.
4. Parasites : These organisms lives in or on other organisms, and obtain food from them. E.g. Tick.
• Decomposers : Organisms that decompose complex substance into simpler ones. E.g bacteria , fungi, etc.
• Abiotic components of ecosystems : Are factors that affects activities of ecosystem. E.g. soil,water, sunlight, etc.
• Food chain : Series of organism which feed on one another.
• Trophic level : [Refer the video to understand in detail]

• Energy transfer in food chain :  [Refer the video to understand in detail]
• Producers obtain energy from sunlight and prepares food which is utilized by rest of ecosystem.
• Energy continuously decreases with increase in level of food chain. Only 10% of energy is transferred to next trophic level. It is transferred in unidirectional way from producers to next trophic level.
• Number of organisms in lower trophic level is always greater than  in higher trophic level.
• One organism is eaten by two or more individuals hence, it forms complex network of food chains called food web.
• Biological Magnification :
• “ Chemical enter in food chains by various means and get accumulated, as the trophic level increases ultimately at highest trophic level the concentration of these chemicals becomes highest.”
• Ozone layer :
• A layer of ozone molecule is located at higher level of earth’s atmosphere. It prevent us from harmful ultraviolet rays emitted from sun.
• Ozone Formation : Ultraviolet rays breaks molecular oxygen into free oxygen atoms. Free oxygen atoms combines with other oxygen atom to form ozone.     

• Ozone Depletion : [Refer the video to understand in detail]
• Chlorofluorocarbons are released in air  where it breaks and release chlorine gas.Chlorine reacts with ozone to form  free oxygen. Free oxygen forms oxygen molecules. Single chlorine molecule destroys thousands of ozone molecules present in ozone layer, which results in depletion of ozone layer.
• Chain reaction is given as :
• CF3Cl ⟶  CF3 + Cl
• Cl + O3 ⟶ ClO + O2
• ClO + O ⟶ Cl + O2   
• Waste disposal : Waste produced from daily activities harm our environment,hence, there is need of proper disposal of waste. Following measures can be taken for proper waste disposal :
• Landfills in which biodegradable waste can be buried in the ground.
• Recycling of waste.
• Incineration.
• Use of products which create less amount of or no waste.