These notes for CBSE Class 10 Science, Chapter 15, 'Our Environment,' explain that the environment comprises our surroundings including air, water, soil, and all living organisms. It details two types of waste: biodegradable and non-biodegradable. The chapter defines an ecosystem as a unit of living and non-living components, with biotic (producers, consumers, decomposers) and abiotic factors. It elaborates on food chains, food webs, and trophic levels, emphasizing the unidirectional flow of energy and the 10% law. The notes also discuss global warming, the formation and importance of the ozone layer, its depletion by CFCs, and biological magnification. Finally, it outlines various waste disposal methods like recycling, composting, incineration, landfill, and sewage treatment, crucial for environmental protection and exam revision.
Last optimized 10 Aug 2026
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The environment includes our physical surroundings like air (or atmosphere), water bodies, soil
(land) and all the organisms such as plants, animals, human beings and micro organisms like
bacteria and fungi (called decomposers).
The waste materials produced by the various activities of man and animals are poisonous
to some extent and can be divided into two main groups :
1. Biodegradable wastes, and
2. Non-biodegradable wastes.
•An ecosystem is a self-contained unit of living things (plants, animals and decomposers),
and their non-living environment (soil, air and water). e.g. a forest, a pond, a lake, a
greenland etc.
?There are two components of an ecosystem : biotic component and abiotic
component.
?Biotic component : It includes three types of organisms:
•Producer
•Consumer
•Decomposer/saprophyte
•Abiotic component
?Consumers can be further divided into three groups : herbivores, carnivores and
omnivores.
•Planktons are very minute or microscopic organisms freely floating on the surface
of water in a pond, lake, river or ocean. Planktons are of two types : Phytoplanktons
and Zooplanktons
•The microscopic aquatic plants freely floating on the surface of water are
called phytoplanktons.
•The microscopic aquatic animals freely floating on water are called zooplanktons. The
freely floating protozoa are an example of zooplankton.
•The micro-organisms which break down the complex organic compounds present in
dead organisms like dead plants and animals and their products like faeces, urine, etc.
into simpler substances are called decomposers.
The sequence of living organisms in a community in which one organism consumes another
organism to transfer food energy, is called a food chain.
A food chain is unidirection where transfer of energy takes place in only one direction.
In aquatic ecosystem of the biosphere, like fresh water ponds, lakes or sea, the food chain starts
with microscopic free floating plants (phytoplankton)
The various steps in a food chain at which the transfer of food (or energy) takes place are called
trophic levels.
The inter-connected food chains operating in an ecosystem which establish a network
of relationships between various species, is called a food web.
The addition of certain pollutants like the carbon dioxide gases increases the temperature of the
earth.
The reduction in the forest cover also contributes to the heating of earth. This is called global
warming.
Ozone Layer formation and importance Ozone (O3) is a molecule formed by three atoms of
oxygen. Ozone, is a deadly poison. It shields the surface of the earth from ultraviolet
(UV) radiation from the Sun. This radiation is highly damaging to organisms.
Ozone at the higher levels ofthe atmosphere is a product of UV radiation acting on oxygen (O2)
molecule. The higher energy UV radiations split apart some molecular oxygen (O2) into free
oxygen (O) atoms.
The deplation of ozone layer is due to CFC (chloro fluorocarbons).
Flow of materials in an ecosystem is cyclic but flow of energy is unidirectional.
There is a continuous transfer of energy from one trophic level of organisms to the next in
a food chain.
Ten percent law states that only 10 percent of the energy entering a particular trophic level of
organisms is available for transfer to the next higher trophic level.
The increase in concentration of harmful chemical substances like pesticides in the body of
living organisms at each trophic level of a food chain is called biological magnification.
The disposal of waste should be done in a scientific way. There are different methods of waste
disposal. The method to be used depends on the nature of the waste. Some of the important
modes of waste disposal are :
(i) Recycling
(ii) Preparation of compost
(iii) Incineration
(iv) Landfill
(v) Sewage treatment
The environment includes our physical surroundings like air, water, soil, and all living organisms such as plants, animals, human beings, and microorganisms.
The two main types of waste are biodegradable wastes and non-biodegradable wastes.
An ecosystem is a self-contained unit of living things (plants, animals, decomposers) and their non-living environment (soil, air, water).
A food chain is the sequence of living organisms in a community where one organism consumes another to transfer food energy.
Global warming is the increase in the Earth's temperature due to the addition of pollutants like carbon dioxide and the reduction in forest cover.
The depletion of the ozone layer is primarily caused by CFCs (chloro-fluorocarbons).
Some important methods of waste disposal include recycling, preparation of compost, incineration, landfill, and sewage treatment.
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