Everything that surrounds us is environment. It includes both living
(biotic) and non-living (abiotic) components.
© Interaction between these biotic and abiotic components form an
© Inan ecosystem living components depend on each other for their food
which give rise to food chains and food webs in nature.
© Human activities lead to environmental problems such as depletion of
ozone layer and production of huge amount of garbage.
All the interacting organisms in an area together with the non-living
constituents of the environment form an ecosystem. £.g., forest, pond etc.
Types of ecosystem : It is of two types :
(a) Natural ecosystem : The ecosystem which exist in nature on its own.
E.g., forest, lake, ocean.
(b) Artifical ecosystem : Man-made ecosystems are called artificial
ecosystem. F.g., crop field, aquarium, garden.
Components of an ecosystem
(Air, water, land) (Plant, animals)
(a) Abiotic Components : All the non-living components such as air,
water, land, light, temperature etc. form the abiotic components.
(b) Biotic Components : All the living components such as plants,
animals, bacteria, fungi etc. form the biotic components.
On the basis of nutrition biotic components are further divided into :
Producers : All green plants and blue-green algae can produce their own
food using abiotic components (photosynthesis), hence called producers.
Consumers : Include all animals which depend on producers directly or
indirectly for their food.
Consumers are further divided into :
(i) Herbivores : Plant eaters e.g., goat, deer.
(ii) Carnivores : Flash eaters e.g., tiger, crocodile.
(iii) Omnivores : Eats both plants and animals e.g., human.
(iv) Parasites : Live on the body of host and take food from it e.g., lice,
Decomposers : Include organisms which decompose the dead plants and
animals e.g., bacteria, fungi. These help in the replenishment of natural resources.
® Food chain is a series of organisms in which one organism eats another
organism as food. For e.g.,
Grass > Deer > Lion
® Ina food chain various steps where transfer of energy takes place is called
a trophic level.
Flow of energy between trophic levels
© Flow of energy in a food chain is unidirectional.
® Green plants capture 1% of sunlight and convert it into food energy.
° Biological magnification : The concentration of harmful chemicals
increases with every next trophic level in a food chain. This is called
® Maximum concentration of such chemicals get accumulated in human
bodies as human occupy the top level in any food chain.
Food web : In nature large numbers of food chains are interconnected
forming a food web.
Environmental problems : Changes in the environment affect us and our
activities change the environment around us. Human activities leads to pollution,
® Ozone layer is a protective blanket around the earth which absorbs most
of the harmful UV (ultraviolet) radiations of the sunlight, thus protecting
living beings from many health hazards such as skin cancer, cataract,
destruction of plants etc.
* Ozone (O,) layer is present at higher levels of atmosphere (i.e.,
stratosphere). It is a deadly poison at ground level.
Formation of ozone molecule
(i) The high energy UV radiations break down the O, molecules into free
oxygen (O) atoms.
(ii) These oxygen atoms then combine with oxygen (O,) molecule to form
the ozone molecule.
0, +O > 0, (ozone)
Depletion of ozone layer
© The decrease in the thickness of ozone layer over Antarctica was first
observed in 1985 and was termed as ozone hole.
® This decrease was linked to excessive use of synthetic chemicals
like chlorofluorocarbons (CFCs) which are used in refrigerators, ACs,
fire-extinguishers, aerosols sprays etc.
® United Nations Environment Programme (UNEP) succeeded in forging
an agreement to stop CFC production at 1986 levels (K YOTO PROTOCOL)
by all countries.
Improvements in lifestyle have resulted in accumulation of large amounts of
Garbage contains following type of materials :
(a) Biodegradable : Substances which can be decomposed by the action
of micro-organisms are called biodegradable wastes.
E.g., fruit and vegetable peels, cotton, jute, dung, paper, etc.
(b) Non-biodegradable wastes : Substances which cannot be decomposed
by the action of micro-organisms are called non-biodegradable wastes.
E.g., plastic, polythenes, metals, synthetic fibres, radioactive wastes,
Micro-organisms release enzymes which decompose the materials but these
enzymes are specific in their action that’s why enzymes cannot decompose all
Science Class – 10
Some methods of waste disposal
(a) Biogas plant : Biodegradable waste can be used in biogas plant to
produce biogas and manure.
(b) Sewage treatment plant : The drain water can be cleaned in sewage
treatment plant before adding it to rivers.
(c) Land fillings : The wastes are buried in low lying areas and are
compacted by rolling with bulldozers.
(d) Composting : Organic wastes are filled in a compost pit and covered
with a layer of soil, after about three months garbage changes to
(e) Recycling : Non-biodegradable wastes are recycled to make new
(f) Reuse : It is a conventional technique to use an item again e.g.,
newspaper for making envelops.