Class X: Our Environment

1. ENVIRONMENT is a sum total of all external factors, substances, living beings, and conditions that surround an organism and influence the same without becoming part of it.

2. All the interacting organisms in an area together with the non-living constituents of the environment form an ECOSYSTEM. an ecosystem consists of biotic components comprising living organisms and abiotic components comprising physical factors like temperature, rainfall, wind, soil and minerals.

3. Organisms can be grouped as PRODUCERS, CONSUMERS and DECOMPOSERS according to the manner in which they obtain their sustenance from the environment.
(i) Organisms which can make their own food like sugar and starch from inorganic substances using the radiant energy of the Sun in the presence of chlorophyll are called PRODUCERS. Eg. all green plants and certain bluegreen algae.
(ii) Organisms which cannot produce their own food but depend on the producers either directly or indirectly for their sustenance are called CONSUMERS.Consumers can be classed variously as herbivores, carnivores, omnivores and parasites.
(iii) Microorganisms that obtain energy from the chemical breakdown of dead organisms or animals or plant wastes are called DECOMPOSERS. Thus decomposers help in the
replenishment of the natural resources. Eg. Bacteria and fungi

4. BIOTIC COMPONENT: It means the living organisms of the environment – plants, animals, human beings and microorganisms like bacteria and fungi, which are distinguished on the basis of their nutritional relationship.

5. ABIOTIC COMPONENT: It means the non-living part of the environment – air, water, soil and minerals. The climatic or physical factors such as sunlight, temperature, rainfall, humidity, pressure and wind are a part of the abiotic environment.

6. BIODEGRADABLE SUBSTANCES are those substances which are broken down into simpler, harmless substances in nature with due course of time by the biological processes such as the action of microorganisms like certain bacteria. Examples: Domestic waste products, urine and faecal matter, sewage, agricultural residue, paper wood, cloth and cattle dung.

7. NON-BIODEGRADABLE SUBSTANCES are those substances which cannot be broken down into simpler, harmless substances in nature. These substances may be in solid, liquid or gaseous form and may be inert and accumulate in the environment or may be concentrated in the food chain and harm the organisms. Eg. DDT, plastics, polythene bags, insecticides, pesticides, mercury, lead, arsenic, aluminium, radioactive wastes, etc.

8. ECOSYSTEM. It is the structural and functional unit of the biosphere, comprising of all the interacting organisms in an area together with the non-living constituents of the environment. It is consists of biotic or biological components comprising of the living organism and the abiotic components comprising of physical environmental factors eg. Ponds, Aquarium.

9. A garden is an example of an ecosystem. Other types of ecosystems are forests, ponds and lakes. These are NATURAL ecosystems while gardens and crop-fields are human-made(ARTIFICIAL) ecosystems.

10. FOOD CHAIN refers to an arrangement of different biotic groups in a sequence of energy transfer. These biotic groups are producer herbivores and carnivores.

11. TROPHIC LEVELS: These are the various steps or levels in the food chain where the transfer of food or energy takes place. The producers or autotrophs are the first trophic level, the herbivores or primary consumers are the second trophic level, the carnivores or secondary consumers are the third trophic level and the large carnivores or tertiary consumers are the fourth trophic level of the food chain.

a) The green plants in a terrestrial ecosystem capture about 1% of the energy of sunlight that falls on their leaves and converts it into food energy.
b) When green plants are eaten by primary consumers, a great deal of energy is lost as heat to the environment, some amount goes into digestion and in doing work and the rest goes towards growth and reproduction. An average of 10%[also called 10% Law] of the food eaten is turned into its own body and made available for the next level of consumers.
c) Since 10% of 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.
d) There are generally a greater number of individuals at the lower trophic levels of an
ecosystem, the greatest number is of the producers.
e) The flow of energy is unidirectional. The energy that is captured by the autotrophs does not revert back to the solar input and the energy which passes to the herbivores does not come back to autotrophs.
f) As Energy moves progressively through the various trophic levels it is no longer available to the previous level.

13. FOOD WEB: the food chains are interconnected with each other forming a web-like pattern, which is known as food web.Eg. Grass may be eaten by grasshopper as well as rabbit or cattle and each of these herbivores may be eaten by many carnivores such as frog, bird or tiger
depending on their food habits.

14. Food Chain and Food Web:
Food chain 
A food chain is a linear sequence of
organisms in which each organism is eaten
by the next member in the sequence. This
interaction among organisms involves the
transfer of energy from one organism to

It generally includes 3-4 levels.

Food web
Food web is the network of many food chains
which are interlinked together and forms a
multitude of feeding connections among
different organisms of a biotic community.
The levels of food web cannot be calculated
as one organism is eaten by many different

15. BIOLOGICAL MAGNIFICATION also known as biomagnification refers to the increase in the concentration of toxic substances like DDT, chemicals, heavy substances etc. with each successive trophic level of the food chain. The concentration of these toxic substances is highest at the highest trophic level.

16. OZONE (O3) is a molecule formed by three atoms of oxygen. It shields the surface of the earth from ultraviolet (UV) radiation from the Sun. This radiation is highly damaging to organisms, for example, it is known to cause skin cancer in human beings. The amount of ozone in the atmosphere began to drop sharply in the 1980s. This decrease has been linked to synthetic chemicals like chlorofluorocarbons (CFCs) which are used as refrigerants and in fire extinguishers. In 1987, the United Nations Environment Programme (UNEP) succeeded in forging an agreement to freeze CFC production at 1986 levels.

17. The decline of Ozone layer thickness in Antartica was first observed in 1985 and was termed as OZONE HOLE.

18. The different methods of solid wastes disposal commonly used around the world are.
a) Open dumping: A conventional method in which solid wastes dumped in selected areas of a town. It actually causes pollution
b) Land fillings: Wastes are dumped in a low living area and are compacted by rolling with bulldozers
c) Composting: Organic wastes are filled into a compost pit (2m × 1m × 1m). It is then
covered with a thin layer of soil. After about three months the same garbage filled inside
the pit changes into organic manure.
d) Recycling: The solid wastes are broken down into its constituent simpler materials. These materials are then used to make new items. Even non –biodegradable solid wastes like plastic, metal can be recycled.
e) Reuse: A very simple conventional technique of using an item again & again. For Eg.
paper can be reused for making envelops etc.

19. MANAGEMENT OF SOLID WASTES: Waste management includes collection, transport, processing, and disposal of waste materials.

a) Separate bins (blue and green) can be used for disposing of non-biodegradable and
biodegradable wastes respectively.
b) Reduction in the use of non-biodegradable products like plastic.
c) Separation of material, which can be reused or recycled.



For last minute consultation, here notes on ‘Our Environment’.  Read it and it will come in handy.  Do post your comments pointing out good or bad things.

Download in pdf form Notes on ‘Our Environment’

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