The physical and biological world we-live in is called our environment. It has the following three important parts :
1. Living organisms 2. Physical surroundings 3. Meteorological factors (or climatic factors).
• The living organisms which constitute environment are plants; animals, human beings and
micro-organisms.
• The physical surroundings, which make up the environment are land, water bodies and air.
• The meteorological factor or climatic factors, which form a part of our environment, are
sunlight, temperature, rainfall, humidity,
In this chapter we are going to learn about interaction of various factors of the environment
and effect of human activities affecting various biogeochemical cycles or environment.
Effect of human activity is an important factor which causes difference in the environment of different places.
Through overuse, misuse and mismanagement of natural resources to fulfil his needs, man has done great
damage to the environment himself. Various environment problems have arisen as a result of pollution,
increasing population and coming up of advanced science and technology.
There is crowding, very less number of trees, large number of factories, which emit black smoke and large
number of motor vehicles which emit poisonous gases. Moreover, due to large population there is lot of garbage,
which is thrown indiscriminately on roads and other common places. These uncontrolled human activities not only
pollute the city environment like soil, air and water but also harm the living organisms that are so essential
for our survival. All these activities lead to ecological imbalance.
With the increase in human population and advancement in technology waste materials have multiplied in
quantity as well as quality. Contamination of environment with these waste material is called pollution.
Not only the wastes but certain useful materials like fertilizers may also contaminate the environment.
Thus, pollution may be defined as a change in the physical, chemical or biological aspects of environment
which make it harmful for living organisms. Materials or agents which cause pollution of the environment
are termed as pollutants e.g., smoke from vehicles, industries, sewage, various radioactive substances.
Pollutants are categorized into two types.
(a) Biodegradable pollutants (b) Non-biodegradable pollutants
Biodegradable pollutants can be quickly degraded by natural means i.e., by the action of various micro-organisms e.g.,
sewage, paper, wool, bones and wood.
Non-biodegradable pollutants are either not degraded or degraded very slowly. They are not easily broken down e.g.,
DDT, plastics, radioactive wastes, silver foil, aluminium cans, glass and plastics. These pollutants may accumulate in
large concentration as they pass through various food chains. Pollution is of five main types-Air, Water, Land,
Radioactive and Noise.
To prove that some domestic waste materials change their form and structure over time while others remain unchanged over long periods.
Procedure
1. Collect all kinds of waste materials from your home. These waste materials will mainly include:
- kitchen wastes like vegetable and fruit peels, spoilt food, used tea leaves, milk packets and empty cartons
- paper
- empty medicine strips and bottles
- old torn clothes
- plastic bottles
- broken foot wear
- polythenes.
2. Dig a pit at home or in the school.
3. Put all waste material in a pit.
4. Cover the pit with soil and keep it wet.
5. Observe after 15 days.
Conclusion
Few materials change their shape and structure over period of time and are called as biodegradable
materials while others remain unchanged are non-biodegradable. Few biodegradable materials change fast while others take longer time.
From above experiment, it is clear that some of the junk is readily degradable by .the activity of
micro-organisms in nature and materials are recycled but some are not easily degraded like polythene, plastics etc.
Different waste materials produced by various activities of man can be broadly classified into two categories:
1. Biodegradable wastes 2. Non-biodegradable wastes.
Biodegradable wastes materials are those waste materials which can· be broken. down into simpler,
non-poisonous substances by the action of micro-orgarusms. As we know various enzymes are required
to digestlhydrolyse or break food into simpler forms. These enzymes are specific in action and act only
on a specific material. That is why various man made materials like plastic cannot be degraded by action
of bacteria or saprophytes. They can be changed only by physical processes like heat and pressure.
Some examples of biodegradable wastes are : cattle dung, paper, wool, wood, bones, leather,
plant products such as wheat, maize, etc. Many industries also produce biodegradable wastes.
All biodegradable wastes should be treatedptop'erJy before discharging them into soil or water.
Any industrial unit, which dumps untreated wastes into soil or water, should be severely punished.
Recycling of Biodegradable Waste Materials Sometimes biodegradable wastes are recycled. In the recycling process,
the nutrients withdrawn from various nutrient pools are returned back. Use of cattle dung . for the manufacture
of gobar gas and use of waste vegetable matter for preparing compost· are two examples of recycling of biodegradable wastes.
Recycling of waste materials helps in maintaining ecological balance because during this process various nutrients
present in the waste are returned back to the natural poolsfromwher.e they were initially withdrawn.
For example, plants draw various nutrients from soil for their growth.
When the plants die, they change into waste, which can be converted into compost by the action of bacteria.
When compost is added to the soil as manure the various nutrients are returned back to it. Thus, recycling
of waste materials helps in maintaining ecological balance. If the various nutrients are continuously drawn
from the soil but are not returned back, it may create an imbalance in nature.
NON-BIODEGRADABLE WASTES
The waste materials, which cannot be broken down .into simpler substances easily in .nature, are known as
non-biodegradable wastes. Aluminium cans, silver foil, iron .nails, plastics, glass, DDT and radioactive wastes
are some examples of non-biodegradable wastes. These nonbiodegradable wastes are major
pollutantsof the environinent.
Radioactive waste materials are one of the non-biodegrad,able wastes, which can pollute the earth to
dangerous levels of toxicity. These wastes are produced in nuclear reactors, laboratories and hospitals,
which use radioactive substances. These radioactive wastes release high-energy particles,
which are extremely harmful to all living forms, both animals (including man) and plants.
Pollution caused by nuclear wastes assumes a universal dimension because the particles emitted by
radioactive wastes spread far and wide in a short period and hence affect the populations, which are quite away
from the source of pollution. Thus, pollution due to nuclear wastes is nof a problem of a particular
country but is a problem of the whole world.
To conclude, we can say·that recycling of waste materials helps in maintaining the ecological balance in the following ways :
1. Recycling of biodegradable wastes such as biomass helps in returning the various nutrients to the soil.
2. Recycling of non-biodegradable wastes reduces the problem of pollution because disposal of these wastes causes pollution.
3. As a result of recycling of waste materials new resources are not used. For example recycling of paper reduces
the cutting of trees for the manufacture of paper.
4. Recycling reduces the volume of wastes.
5. Recycling is better than incineration as it prevents pollution.
No organism or a species lives alone, always there are associations influencing each other and organising
themselves into communities. The organisms of any community besides interacting among themselves,
always have functional relationship with the environment. This structural and functional system of
communities and their environment is called an ecosystem.
Two main components of ecosystem are: Biotic (living) and Abiotic (Non-living).
BIOTIC COMPONENTS includes autotrophs and heterotrophs (consumers and decomposers).
Classification of Living Organisms
Living organisms are mainly classified as producers, consumers and decomposers.
• Producers include plants and some blue green algae which can make their own food in the form of
organic compounds like sugar and starch by the process of photosynthesis. They are also called autotrophs.
• Consumers depend on producers directly or indirectly. Herbivores directly eating plants are called primary
consumers while carnivores consuming herbivores are secondary consumers.
Both producers and consumers have their life cycles and new generation of population develop while old ones die.
If the materials so locked in the body of the organism are not returned to soil and atmosphere, the cycling of
materials will stop and earth will be full of dead organisms.
There is continuous, breaking up or decomposition of organic materials everywhere in all ecosystems.
This role is played by decomposers.
• Decomposers. Some organisms with a specialized mode of nutrition and life like bacteria, fungi constantly
decompose dead organic materials into simple inorganic substances and during the process derive from them
their food and energy. These are called decomposers or reducers. You can understand role of decomposers
by not cleaning aquarium.
• Parasites. Some of the consumers live on or in other organisms and derive their nourishment from host's body.
They are known as parasites e.g., Tape worm, leech.
ABIOTIC COMPONENTS include materials and energy. Materials are like water, mineral salts, atmospheric gases etc.
and energy is like light, heat, stored energy in chemical bonds etc.
Abiotic part is divided into 3 components:
1. Inorganic substances like carbon, nitrogen etc.
2. Organic compounds like carbohydrates, proteins, fats etc.
3. Climate like temperature, light, pressure etc.
Fig. 3.1 Components of ecosystem
· The materials continuously keep on cycling i.e., entering into the living system and through death and decay
returning to soil and atmosphere. This process in called mineral circulation or the
bio-geochemical cycles.
· While materials keep on cycling, fresh energy is continuously trapped from the sun by green plants on one
hand and lost in space through respiration by all types of organisms.
· Terrestrial ecosystem are named after the type of organism and habital conditions, such as grassland
ecosystem, crop ecosystem, forest ecosystem and desert ecosystem.
· Fresh water ecosystems are usually named upon the size and nature of fresh water body, such as
river ecosystem, pond ecosystem, lake ecosystem.
· Marine ecosystem is the largest and most uniform aquatic ecosystem.
Some of the ecosystems are man made and are called artificial ecosystem. e.g., garden, aquarium etc.
Ecosystem is a functional system which in balanced condition is self-sufficient and self-regulated.
But at the same time, several ecosystems are interrelated and combine to form larger ecosystem. e.g.,
the tree ecosystem in association with have variety of other trees, smaller plants and animals
form forest ecosystem.
· The series of organisms fixing energy, eating and being eaten is called a food chain.
· Each step of a food chain is called a trophic level.
· First trophic level always consist of autotrophs which can fix solar energy.
· Second trophic level is that of herbivores feeding on autotrophs.
· Third trophic level includes primary consumers feeding on herbivores.
· Fourth trophic level includes secondary consumers which feed on primary consumers.
Food chain can be traced in any ecosystem e.g.,
Food chain in a grassland
Grass —® Grasshopper —® Frog —® Snake —® Vulture.
Food chain in a forest
Plants —® Deer —® Lion.
Food chain in a pond
Phytoplanktons —® Zoo planktons —® small fish —® big fish.
· The food chain starting from the green plants through herbivores to top carnivore is called grazing food chain.
· Food chain starting from the dead organic matter being consumed by detritus feeding micro-organisms which
in turn are eaten by some other predators is called detritus food chain.
In order to understand how an imbalance is created due to disruption of food chains by man's activities,
let us consider the food chain
Grasses —® Deers —® Lions.
1. In the above food chain, if all the lions are removed, the population of deer will increase since there won't be
any lions to kill them and keep the population under control. This will lead to high consumption of grasses
(producers) and may even eliminate them.
2. If the deer population is removed instead of lions, it will lead to decrease of lion population since there
will not be any prey. The lions may even resort to other preys such as domestic animals or man to survive.
If the deer and lion operate in other food chains in a food web, then the removal of any of them will lead to
disruption of the food web and will cause disturbance in the ecosystem
3. If the grasses (producers) are removed, then all life will come to an end. If there is no there will be no herbivores.
If there are no herbivores, there will be no carnivores. ultimately all organisms will die.
• The food relations are not always simple chain like but forms complicated network.
The netlike trophic interrelationship is called a food web.
• In a food web, one organism may be linked with several others in an interlocking food linked into a network.
• In all ecosystems not only the different grazing food chains get interlocked but the detritus chain also get interconnected.
• At each trophic level some energy is used for itself, some passes to the next trophic organisms as food and some is
routed to the detritus food chain by way of excretion.
Food chains do not operate in isolation i.e., various food chains are interconnected to each other forming a complex network.
For example, food chains in a grassland, a forest, a crop field or a pond form a network with intercrossed and linkages.
Grass may be consumed by rabbit which is in turn consumed by hawks. The grass is also consumed by insects which in
turn are consumed by frogs. Frogs are consumed by snakes and snakes by hawks.
The network formed by various food chains which are interconnected with each other is called a
food-web.
A particular organism may occupy position in more than one food chains. For example, in the food web shown above,
mice are present in two food chains. These chains are :
Fig.3.2 A Food Web
Plants —® Mice —® Snakes —® Hawks
Plants —® Mice —® Hawks
In the first food chain mice are consumed by snakes whereas in the second food chain they are consumed by hawks.
Other food chains operating in this food web are :
Plants —® Grasshopper —® Frogs —® Snakes —® Howks
Plants —® Grasshopper —® Insects —® Frogs —® Snakes —® Howks
Plants —® Rabbits —® Hawks
Plants —® Seed eating birds —® Howks.
In a food chain, food which provides energy is transferred stepwise from one trophic level to another.
Thus, energy is used and conveyed from one trophic level to another. This process is called 'flow of energy'.
It is a one way process and energy once used by the food chain of an ecosystem is lost forever.
The initial level where energy from the environment enters the living components is at the producer level.
Green plants trap solar energy from the sun and utilize it for photosynthesis. Plants are able to trap the sun's
energy due to the presence of green pigment, chlorophyll, present in them.
This process converts solar energy into chemical energy which is stored as carbohydrates.
About 1% of the total sun's energy that reaches earth is used up in photosynthesis.
The chemical energy stored in plants is used up in their respiration growth (tissue building) and repair.
Some of the energy is not utilized and is released into the community environment.
Plants are consumed by herbivores (First order consumers). The chemical energy stored in the plants as
carbohydrates is consumed by herbivores as food. A portion of this energy is used for metabolic activities
and growth of the herbivores. Some of the energy is not utilized and is released by these animals as heat
into the environment.
The herbivores are consumed by carnivores (Second order consumers) and the same process is repeated
as in herbivores and unutilized energy is released into the environment by these animals as heat.
The amount of energy which is released as heat into the environment is taken to be lost.
It may be noted that a part of the energy at each trophic level is transferred to the decomposers or decay organisms.
The decomposers utilize a part of this energy for maintaining their life prpcesses.
The unutilized energy is released as heat into the environment.
From above discuussion we conclude :
• One percent of solar energy is trapped by green plants and is converted into food energy by the of process of photosynthesis.
• Part of the chemical energy in plant tissues is passed from organism to organism as they are successively eaten.
• Ultimately the entire energy trapped by green plants at one time is lost from the ecosystem in several stages.
• 10% energy is passed from one trophic level to another. e.g., when green plants are eaten by herbivores then only
10% of the energy available with plants is passed to them.
• Most of the heat i.e., 80% is lost as heat to the environment and some is used to carry out various metabolic
activities like digestion, growth, reproduction etc., and doing work.
• Energy therefore does not move in a free condition, but rather through organic materials from one trophic level to another.
• One important concept of ecological energetics is that energy always flows in one direction in the ecosystem
while materials like carbon, nitrogen, hydrogen, oxygen etc. are repeatedly used in the ecosystem cycling from
inorganic to organic and back to inorganic forms.
• Since very small amount of energy is passed to the next trophic level, food chains consist of three to four steps.
After this, energy left is not sufficient to survive.
• At each trophic level, some energy is transferred to the decomposers. The decomposers utilize a part
of this energy for maintaining their life processes.
• There is a loss of energy at each energy transfer in various trophic levels, which is lost to the environment in the form of heat.
Therefore, the amount of energy available at each successive level is less than
the previous level.
Fig. 3.3
Studies of various food chains show that the energy available at each successive level is 10% of the previous level.
This is called the 10 per cent law. In the given illustration, 1000 J of energy is available to the plants from the sun.
Plants convert 1 per cent of this energy into chemical energy. Thus, 10 J of energy is stored in plants. This energy
is available to herbivores. Herbivores retain 10 per cent of 10 J i.e., 1 J as stored energy and 9 J of energy would be
lost to the environment. Thus, only 1 J of energy would be available to carnivore as food.
The flow of energy in the living components of the biosphere is unidirectional.
The energy enters the living components from non-living environment through photosynthesis.
The radiant energy of sun converted into chemical energy is never converted back into radiant energy but is dissipated
into the atmosphere as heat at every step. In food chain, a large amount of energy remains unutilized and is lost to
the environment as heat at each trophic level. The energy lost as heat to the environment cannot be reutilized by
plants for photosynthesis.
Energy transfers in the biosphere in food chains obey the laws of thermodynamics.
• The first law of thermodynamics says that energy can be converted from one form to another but can never be
created or destroyed. In a food chain it is observed that energy is converted from one form to another.
It is frequently transformed into heat energy which is unusable and is released into the environment.
But the energy itself is not destroyed.
• According to the second law of thermodynamics energy transformation is never completely efficient.
Whenever energy is transformed from one form to another, there is a decrease in the amount of useful energy;
a part of energy is converted into heat. Thus, energy transformation in the biosphere among living organisms
obeys the laws of thermodynamics.
Vegetarian food habits can provide more energy :
It can be observed that with successive trophic levels, there is decrease in the amount of energy available.
Hence, if we are closer to the producer level, we can get more energy (calories) from the food because
at the producer level, the amount of energy available is the highest. Consider the two food chains
involving man as given below :
Producers (Plants) —® Goat —® Man
Producers (Plants) —® Man
In the second food chain, man is closer to producer level and hence he gets more energy. On the other
hand in the first food chain involving three steps man is away from the producer level and hence gets less energy.
As an illustration, let us consider a case in which plants receive 1000 J of energy from the sun. Plants convert 1%
of the solar energy into food. Thus, 10 J of energy would be stored in plants as food. Now, if the man is
vegetarian then he would get 10 J of energy by eating plants.
Plants Man
However, if the man is non-vegetarian he would receive only 1 J of energy by eating meat in a three step food chain
Plants Goat Man
Here goat receives 10 J of energy and transfers 10% to man. Thus, a non-vegetarian man receives only 1 J of energy.
From this we conclude that vegetarian food habits provide more energy than
non-vegetarians.
Food chains involving various living organisms in a community can also be represented in a graphical
manner by drawing pyramids called ecological pyramids.
An ecological pyramid is a graphical representation of a specific parameter
(such as number, biomass or energy) of a food chain.
Ecological pyramids have various levels. The producer level is represented by the base of the pyramid.
And as the trophic levels increase the pyramid goes on tapering upwards.
The carnivores are on top of the pyramid.
Ecological pyramids can be of various types-pyramid of number, pyramid of biomass, pyramid of energy.
Pyramid of number is constructed on the basis of the number of organisms at each level. Pyramid of weight
is constructed on the basis of biomass of all the organisms at each trophic level. Pyramid of energy is
constituted on the basis of the energy contained in all the organisms at each trophic level.
Pyramid of numbers is constructed on the basis of the number of organisms at each trophic level in the food chain.
In a food chain, the number of animals decreases at successive trophic levels. At the bottom of the pyramid are
the green plants which synthesize food through photosynthesis, using sun's energy.
Just above the plants are herbivores. The animals at the lowest level of the pyramid are large in number.
At the successive higher levels of the pyramid, the number of animals decreases.
The top carnivores at the top of the pyramid are very few. For example, in a forest there may be large number
of deers but there will be only a few lions.
Fig.3.4 PYRAMID OF NUMBERS
Biomass means the amount of living matter. The pyramid ofmass is constructed on the basis of mass of all
organisms in each trophic level in the food chain. The total biomass of the plants is greater than that of the herbivores.
The total biomass is greater than that of first order carnivores.
In a food chain only 10 per cent of the biomass is transferred from one trophic level to the next
level in the food chain as illustrated
Fig. 3.5 Pyramid of Biomass
The pyramid of energy is constructed on the basis of total energy contained in all the organisms ofeach trophic
level of the food chain. As discussed earlier, the amount of usable energy decreases at each trophic level in a
food chain because at each step some energy is lost as heat to environment. Plants have the maximum store
of chemical energy. Herbivores have less energy which is only about 10 per cent of the energy stored in plants.
Only 10 per cent of the chemical energy of previous level is retained by the next trophic level.
This is called 10 per cent law. As an illustration let us assume that 10 J of energy is stored in plants.
Herbivores feeding upon them would retain 1 J (10% of 10 J ) of energy. Carnivores feeding on herbivores
would gain 0.1 J (10% of 1 J) of usable energy. This is illustrated
Fig. 3.6 Pyramid of Energy
Biomagnification is another aspect of food chain in which harmful chemicals enter food chains and are
passed from one trophic level to another getting concentrated at each level.
ACCUMULATION OF HARMFUL CHEMlCALS IN FOOD CHAINS
It is seen that through the food chain some harmful chemicals enter our bodies. We know that pesticides
and insecticides are used to protect crops from diseases and pests. These chemicals enter
the soil and gradually either enter the water table or get absorbed by plants along with water and mineral salts.
Thus, they enter the food chain at the producer leveL At each trophic level these harmful chemicals get more and
more concentrated and ultimately reach our bodies. It has been shown by studies that humans have higher
concentration of these chemicals than organisms lower in the food chain. For example, DDT which is used against
mosquitoes is present in the highest concentration in human beings. Thus, we can conclude that an organism
which is on the extreme right .ofthe food chain, has the maximum concentration ofthe harmful chemicals in its body.
This phenomenon is known as biomagriification or biological magnification. The following example illustrates the
phenomenon of biomagnification.
The process of concentration of harmful chemicals such as pesticides, at each successive step in a food
chain is called biological magnification.
Man being an omnivorous, eats fish, meat as well as vegetables. Being a powerful and intelligent animal,
he is very rarely eaten by any animaL Moreover he disposes his dead ones in such a way that scavengers
do generally not consume them. Thus, he is at the top of most food chains. In other words,
he is only a consumer. As a result of pollution, there are greater chances of accumulation of harmful
chemicals in his body, which can be very harmful.
Accumulation of Metallic effluent like mercury and fluorine are very harmful for human health.
Mercury can lead to disease namely Minamata and fluorine can lead to knee-knock syndrome i.e.,
bending of legs. Fluorine may also cause fluorosis.
• Methods to reduce intake of pesticides
— Use of manures rather than fertilizers.
— Minimum use of chemicals like pesticides etc.
Instead biological method should be used to control insects and pests.
— Disease resistant varieties of crops should be developed by using hybridisation technique.
— Domestic and Industrial wastes should not be disposed in lakes and rivers.
— Wash fruits and vegetables before their consumption.
Some of the activities of man have disturbed the environment:
1. Deforestation
• For getting wood for fuel and furniture.
• For developing fields for cultivation.
• For developing urban areas.
2. Mining to get various minerals, coal and petroleum.
3. Use of large number of vehicles for transportation.
4. Generation of electricity through
• Thermal power plants.
• Hydroelectric power plants.
• Nuclear power plants.
5. Construction of roads, railway tracks etc.
6. Development of many harmful products such as plastics.
7. Extensive use of pesticides and other chemicals.
8. Use of chlorofluorocarbons.
Various human activities change the environment and affect us. In this chapter we are going to
discuss two major environmental problems i.e.
• Ozone layer depletion. • Waste disposal.
As we know that around 23 km from the surface of the earth there is a thick layer of ozone gas.
It is formed by the action of sun's rays on oxygen. This thick layer of ozone also called ozone blanket is very
effective in absorbing ultraviolet radiations given out by the sun. Thus, it protects the earth from the harmful
effects of ultraviolet rays. In the year 1980 scientists noticed a 'hole' in the ozone blanket covering the upper
surface around Antarctica. This fact is of great concern as harmful ultraviolet rays can now come to the earth
through this hole. This will increase the level of uV-rays reaching the earth. An increased level of ultraviolet
rays is very harmful as it can cause skin cancer and genetic disorders.
Main cause of depletion of ozone layer is chlorofluorocarbons (CFCs). Another cause of depletion of ozone layer
is emissions from jet aeroplanes. Chlorofluorocarbons have the largest ozone d.epletion potential (ODP).
Chlorofluorocarbons when released from air conditioners, refrigerators, spray cans and industrial solvents drift in
the stratosphere very slowly. Therefore, each chlorine atom form chlorofluorocarbons gets sufficient time to
destroy a large number of ozone molecules
(approx. 100,000). The first chlorofluorocarbons produced in 1931 are still in the sky today. Now, all over the world,
the use of. chlorofluorocarbons is being banned.
• Ozone iN our atmosphere is formed by interaction between oxygen molecules and ultraviolet light as follows :
U.V. light + O2 —® O + O
• Single atoms of oxygen are very reactive and combine with O2 to form O3 i.e., ozone
2O + 2O2 —® 2O3
There are three main causes of ozone depletion :
1. Human activity is by far the most prevalent and destructive source of ozone depletion, while threatening
volcanic eruptions are less common. Human activity, such as the release of various compounds containing chlorine
or bromine, accounts for approximately 75 to 85 per cent of ozone damage. Perhaps the most evident and destructive
molecule of this description is chlorofluorocarbon (CFC). CFCs were first used to clean electronic circuit boards,
and as time progressed, were used in aerosols and coolants, such as refrigerators and air conditioners.
• When CFCs from these products are released into the atmosphere, the destruction begins .
• As CFCs are emitted, the molecules float toward the ozone rich stratosphere.
• Then, when UV radiation contacts the CFC molecule, this causes one chlorine atom to liberate.
• This free chlorine then reacts with an ozone (O3) molecule to form chlorine monoxide (ClO) and a
single oxygen molecule (O2). This reaction can be illustrated by the following chemical equation
Cl + O3 —® O2 + ClO
• Then, a single oxygen atom reacts with a chlorine monoxide molecule, causing the formation of an
oxygen molecule (O2) and a single chlorine atom
O + ClO —® Cl + O2
• This threatening chlorine atom then continues the cycle·and resuits' in further destruction of the ozone layer.
• Measures have been taken to reduce the amount of CFC emission, but since CFCs have a life · span of 20-100 years,
previously emitted CFCs will do damage for years to come.
Fig. 3.7 IntraCtion of CFCs and UV radiationS damaging the ozone layer.
2. Natural sources also contribute to the depletion of the ozone layer, but not nearly as much as human activity.
Natural sources can be blamed for approximately 15 to 20 per cent of ozone damage. A common natural source of
ozone damage is naturally occurring chlorine. Naturally occurring chlorine, like the chlorine released from the
reaction between a CFC molecule and IN radiation, also has detrimental effects and poses danger.to the earth.
3. Volcanic eruptions are a small contributor to ozone damage, accounting for one to five per cent.
During large volcanic eruptions, chlorine, as a component of hydrochloric acid (HCl), is released directly into the
stratosphere, along with sulphur dioxide. In this case, sulfur dioxide is more harmful than chlorine because it is
converted into sulphuric acid aerosols. These aerosols accelerate damaging chemical reactions,
which cause chlorine to destroy ozone.
Some of the environmental, social and economic effects of ozone depletion are :
1. Plant growth and productivity. UV radiations can affect plant growth and productivity.
2. Marine food chain. Phytoplanktons are microscopic plants that forin the basis of the marine food chain.
These are particularly susceptible to increases in UV radiation. Reduced phytoplankton numbers would
significantly effect other marine species, including commercial fish stocks.
3. Human health. At high exposure levels, UV radiations can weaken the human iminune system and
causes skin cancer, cataracts and eye cancer. Increased levels of UV radiation will contribute to rising Incidences of skin cancer.
4. Deterioration of materials. Increased UV radiat~ons can accelerate the deterioration of plastics, wood, paper, cotton and wool.
The currently available substitutes of chlorofluorocarbons are hydrochlorofluorocarbons (HCFCs) and
hydrofluorocarbons (HFCs). HCFCs contain one chlorine atom less than CFCs and are less harmful than CFCs.
HFCs have no chlorine and hence ozone friendly. So, the ideal solution seems to be to use HFCs.
But all the three gases are greenhouse gases and have global warming potential.
Montreal Protocol. In 1987, 27 countries signed international agreement to protect stratosphericozone.
The main points were :
• To limit the production and use of ozone depleting substances.
• Phasing out of ozone depleting substances.
• Helping the developing countries to implement use of alternatives as CFCs.
Uptill now more than 175 countries have signed the Montreal Protocol.
In 1987, the United Nations Environment Programme (UNEP) succeeded in forging an agreement
to freeze CFC production at 1986 levels.
• Tasmania lies in the region of the Southern Hemisphere where the first signs of ozone recovery are most
likely to 'be detected, possibly around 2010-2015.
• There has been a rapid decline in the amount of ozone over the Antarctic regions since the 1970s,
leading to the formation of the ozone 'hole'.
• Between 1998 and 2001 the ozone hole covered an area of up to 26 million km2, nearly three
times the area of Australia.
• Despite the reduction in use and emissions of ODSs (Ozone depletion substances), it is likely that.
evidence of ozone recovery will not be seen until about 2010-2015, as the various ODSs causing the
decline continue to persist in the atmosphere.
• In the meantime, Tasmania will experience minimum ozone levels for the next 10 to 15 years.
• There is uncertainty about the timing of the recovery of the ozone layer. The size and duration of
the Antarctic ozone 'hole' was greatly reduced in 2002, but recovery of the ozone layer remains inconclusive.
(in the 2003 ozone hole was the largest yet recorded).
With the rise in population there has been increase in solid wastes from domestic and commercial wastes
which lead to land pollution. It is a serious problem specially in large cities where disposable containers are used.
Heaps of wastes are found to be lying hen and there. Many of the wastes do not decompose at all while the organic
wastes which decompose release foul smell. Few wastes when burnt, release harmful fumes.
Problem of land pollution needs to be sorted out scientifically.
1. Solid wastes from industrial, agricultural field etc.
2. Cow dung from cattle shed.
3. Sewage.
4. Various waste materials like plastics, papers, clothes, rubber, metals, peelings of fruits and
vegetables are responsible for land pollution.
5. Unserviceable wooden articles.
6. Leftover eatables.
7. Food items spoilt due to fungal growth.
8. Sand and bricks.
9. Empty bottles.
10. Leather goods.
11. Ash.
1. Foul smell released by decomposition of organic wastes.
2. Blocking of the flow of water in the drains.
3. Dirty surroundings.
4. Breeding grounds of houseflies, mosquitoes.
5. Consumption of polluted water leads to spreading of various water borne diseases like cholera, diarrhoea and dysentery.
6. Burning of some wastes leads to production of smoke which is harmful for health.
7. Certain chemicals like lead, sulphur which are released from various industries finally come to land and act as land pollutants.
1. Use of biodegradable wastes.
2. Recycling of certain waste products like plastics and paper help in controlling water pollution.
3. Organic wastes can be sent to biogas plants.
4. Molten plastic wastes and asphalt can be used for making roads.
5. Volume of wastes can be reduced by burning them at high temperature. This is known as incineration.
In this method huge volumes of waste materials from houses, hospitals, industries are burnt and thus
leaving behind less amount of ash.
Fig. 3.8 INCINERATOR
This can be done in an incinerator.
6. Biodegradable and non-biodegradable wastes should be disposed of separately.
7. Various metals can be melted and recycled.
8. Organic wastes can be buried and used as a manure after the process of composting.
9. Use of manures and bio-fertilizers can reduce the need for chemical fertilizers.
10. By improving the mining techniques, spread of mine dust can be reduced.
Solid wastes generated by domestic, commercial and industrial activities are often indiscriminately disposed.
Unscientific management of such wastes leads to serious environmental problems.
The problems are already acute in cities and towns, as the disposal facilities are not keeping pace with the quantum
of waste being generated. It is very common to find large heaps of garbage in disorganized manner at every
nook and corner of the cities.
In sanitary method being adopted for disposal of solid wastes is a serious health concern. Particularly,
during rainy season, run-off and high humid conditions increase the health hazards. The landfill sites,
which are not well maintained, are prone to groundwater contamination due to leachate percolation.
Open dumping of garbage serves as breeding ground for disease vectors such as flies, mosquitoes,
cockroaches, rats and other pests.
High risks of spreading diseases like typhoid, cholera, dysentery, yellow fever, encephalitis, plague and dengue
fever may not be ruled out. There are three major ste:ps involved in the management of garbage viz.
collection, transportation and disposal.
It is estimated that solid waste generated in small, medium and large cities and towns is about 0.1 kg,
0.3-0.4 kg and 0.5 kg per capita per day respectively.
The composition of garbage in India indicates lower organic matter and high ash or dust contents.
It has been.estimated that recyclable content in solid wastes varies from 13 to 20% and combustible
material is about 80-85%. A typical composition of municipal solid waste is given below.
PRESENT GARBAGE MANAGEMENT PRACTICES
Collection of Garbage
Garbage is generated from residential and commercial complexes. Current practices in residential
areas for collection of garbage differ from city to city.
Collection Centres
Each city has its own system for setting up of waste collection centers. The waste is collected from
communities in a smaller bin, which is then transported, to larger bins known as secondary collection facility.
Transportation of Garbage
Transportation of waste from collection centers to final disposal site is another important step in the management
of garbage. It has been estimated that approximately 60% ·of waste is collected for transportation to the disposal sites.
Disposal of Garbage
The disposal of garbage in a well-managed land, adopting scientific methods of operation is termed as sanitary land-fill (SLF).
Most important aspect relating to landfill is, identification of a suitable site. Landfilling is a slow and time consuming process.
Most of the landfill sites in India are uncontrolled dumps and are not sanitary landfills where domestic, commercial,
industrial and hospital wastes are dumped together. The garbage on such sites is not properly speedy and compacted.
Thus, sites identified for filling are not properly maintained.
Community Participation
• Creating mass awareness, ensuring public participation in segregation of recyclable material and storage of waste at source;
• Ensuring public participation in community based primary collection system;
• Organizing ragpickers for collection of recyclable material at the community level;
• Providing health education to the ragpickers and suggesting tools for safety;
• Providing employment through organizing door to door collection of waste; and encouraging minimization ofwaste through
in-house backyard composting, vermiculture and biogas generation etc;
• Recycling;
• Wealth from wastes: technologies;
• In the recent past, private sectors have taken initiatives to use the garbage as profitable venture, Incineration, Composting, Vermiculture.
Sewage treatment includes the following three steps :
(a) Primary treatment.
It includes sedimentation, filteration, floatation and passing wastes through thick layer of gravel. After tris, sewage is neutralized.
(b) Secondary (Biological) treatment.
Neutralized material is sent to Upflow Anaerobic Sludge Blanket (UASB) where anaerobic bacteria act on biodegradable material.
Mixing wastes with sludge containing bacteria and algae for consumption of organic matter and release of oxygen can prove to be
useful in treatment of sewage. Digestion of organic material by bacteria is called biological or secondary treatment.
(c) Tertiary treatment.
Chlorination, evaporation, exchange and absorption constitute tertiary treatment. This treatment is meant for disinfection
of the wastes and the removal of all inorganic wastes.
With changing time we depend mainly on disposable and packed materials which are nonbiodegrable.
This has negative impact on our environment. Because of the rising problems arising as a result of disposal of
non-biodegradable materials, like plastic cups used for tea, some alternative ways were thought. Kulhads made
of clay replaced plastic cups. But later it was realized that making of lot of Kulhads led to loss of fertile top soil.
This idea was dropped and presently disposable paper cups are used. These can De recycled and does not
cause any environmental hazard.
Q.1 Why are some substan es biodegradable and some non-biodegradable?
Ans. Biodegradable substances are organic substances obtained from plants and animals wastes which are
degraded by microorganisms like bacteria and fungi. The microorganisms present in our environment
secrete enzymes that degrade wastes into simpler substances. These substances increase the fertility of soil.
Whereas there are some substances which are not broken down into simpler substances by the action of
microorganisms and persist as such in the environment. They are called non-biodegradable subsntaces.
For example, plastic, glass, synthetic chemicals, aluminium cans, etc. These substances,
thus persist in the environment and pollute it.
Q.2 Give any two, ways in which biodegradable substances would affect the environment
Ans. The two ways in which biodegradable wastes pollute the environment are as follows:
(i) Decomposition of these wastes produces foul smell which spreads in the
surroundings and makes the life of people miserable.
(ii) Heaps of garbage acts as a breeding ground for flies and other parasites.
They carry number of pathogens and spread diseases such as diarrhoea,
typhoid, cholera, tuberculosis, etc.
Q.3 Give any two ways inwhich non-biodegradable substances would affect the environment
Ans. (i) Some of the non-biodegradable chemicals like pesticides (DDT) and heavy metals enter the
food chain and biomagnify in each trophic level. They accumulate in the body tissues of
living organsims and cause various diseases. Humans are harmed the most because humans
lie at the top of food chain.
(ii) Excessive use of non-biodegradable fertilisers and pesticides affect the fertility of soil and
subsequently reduce the cropy yield. The soil may become acidic or alkaline.
Q.4 What are trophic levels? give an example of a food chain and state the differeny trophic levels in it.
Ans. The distinct sequential steps of a food chain where transfer of energy occurs are called trophic levels.
Let us consider a food chain:
Plants ¾® Rabbit ¾® Fox ¾® Lion
In the above food chain, plants are the producers which convert solar energy into chemical energy of
organic compound by the process of photosynthesis. Thus, they form the first trophic level in tlle food chain.
A rabbit is a herbivore (primary consumer) and eats plants. Here transfer of energy occurs from the plant to herbivore.
Thus rabbit belongs to second trophic level. Rabbit, in turn, is eaten by the fox (secondary consumer) a carnivore, thus,
fox belongs to third trophic level. Lion is the top carnivore which eats fox and represents fourth trophic level.
Q.5 What is the role of decomposers in the ecosystem?
Ans. Decomposers are microorganisms (bacteria and fungi) which obtain nourislunent from organic remains.
They are essential components of an ecosystem. They decompose dead remains of plants and animals into
simple inorganic compounds hence act as cleansing agents of environment. These simple compounds are
released into the environment (soil, air, water) from where they are used by the producers as raw materials.
Thus, they help in cycling of nutrients in an ecosystem and make the soil fertile.
Q.6 What is ozone and how does it affect any ecosystem?
Ans. Ozone is an isotope of oxygen containing three atoms of oxygen (O3). It is present in the stratosphere about
16-50 km of height above equator and 8-30 km above poles where it is formed from O2 by the action
of high energy UV rays.
Ozone is formed when atomic oxygen combines with oxygen.
The ozone layer protects all forms of life on earth from harmful UV radiations coming from the sun. Certain harmful
chemicals such as CFCs (chlorofuorocarbons), methane (CH4), oxides of nitrogen (NOx), etc., released by various
human activities are destroying the ozone layer and making it thin. As a result, more and more harmful radiations
(UV radiations) are reaching the earth surface that are responsible for causing various diseases such as skin cancer,
cataract, damage to immune system in human beings and animals. They also result in increased rate of embryonic mortality,
decreased photosynthesis in plants and also contribute towards global warming.
Q.7 How can you help in reducing the problems of waste disposal? Give any two methods.
Ans. Waste disposal is the biggest problem of all local bodies. We can help in reducing the problem of waste
disposal by changing our lifestyle and attitude.
(i) We should try to minimise use of non-biodegradable articles and switch over to use of such articles
that can be recycled or are made of biodegradable materials.
(ii) The kitchen wastes should be converted into compost that can be used in gardens and lawns.
The non-biodegradable wastes should be disposed off properly, for example, landfill, burning and incineration.
Q.8 What will happen if we kill all the organisim of one trophic level?
Ans. If we kill all the organisms in one trophic level, the transfer of food to the next trophic level will stop.
There will be overpopulation of individuals belonging to the previous trophic level which would have been eaten otherwise.
Thus, the ecological balance will be disturbed because the increase in number of organisms will be much beyond the carrying
capacity of the environment. There will be no transfer of food from one trophic level to another.
Q.9 Will the impact of removing all the organisms in a trophic level be different for different trophic levels?
Can the organisms of any trophic level be removed without causing any damage to the ecosystem?
Ans. The impact of removing all the organisms in a trophic level will differ from organism to organism.
If an organism is removed from an ecosystem, it will definitely affect the transfer of energy and nutrients
in the environment because all of them are linked together in a food chain. Thus, the removal of an organism
from a trophic level will ultimately affect the ecosystem. For example, removal of producers will kill all the consumers.
If all the herbivores are removed, then all the carnivores will die due to starvation. Killing of carnivores will increase
the number of herbivores that in tumwill eat up all the producers.
No, all the organisms of any trophic level cannot be removed without causing any damage to the environment as they
are linked through a food chain and survival of organisms of one tropic level depends on the existence of the
members of other trophic level.
Q.10 What is biological magnification? Will the levels of this magnificaiton be differeny at different levels of the ecosystem?
Ans. Biological magnification is the phenomenon that involves gradual increase in the concentrations of concentraharmful
non-biodegradable chemical substances at different trophic levels in a food chain. Yes, the level fo this magnification
will be different at different trophic levels. It will be minimum in the first trophic level (producers) and maximum in
last trophic level (i.e., top carnivore or omnivore). For example, in a study it was found that concentration of DDT
was 0.02 ppm in water, 5.0 ppm in phytoplanktons, 240 ppm in fishes and 1600 ppm in fish eating birds.
Q.11 What are the problems caused bythe non-biodegradable wastes that we generate?
Ans. (i) Non-biodegradable chemicals enter the food chain, biomagnify and affect human beings and other living
components of the environment.
(ii) Excessive use of non-biodegradable fertilisers and pesticides affect the fertility of soil and subsequently,
reduce the crop yield by making soil acidic or alkaline.
(iii) The volume of non-biodegradable wastes are not decreased by natural process of decomposition.
(iv) Non-biodegradable pesticides and other toxins pollute underground water along with surface water and make them unfit for use.
(v) Recycling of these non-biodegradable materials produces only inferior quality products. During recycling,
they produce various toxins which may be carcinogenic in nature.
Q.12 If all the waste we generate is biodegradable,will this have no impact on the environment?
Ans. If all the waste we generate is biodegradable, it will3.lso have some adverse effect on the environment.
The imapct on the environment will depends upon system of collecting, transporting and disposal of biodegradable waste.
If the degradation is regular and clean, then the impact will be little in urban areas. Only some effects will be observed at
disposable site that will release foul smell and some gases that can contaminate sanitary workers. These contaminations
can be reduced by use of machines and wearing protective gear by workers. If the degradation is not regular,
it acts as a breeding ground for files, insects and microbes which cause various disease. Moreover, the ortting
biodegradable wastes emit foul smell which makes the life of people miserable.
Q.13 Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
Ans. Air pollutants like CFCs, CH4, oxides of nitrogen (NOx) are causing depletion in ozone layer that allows large amount
of UV radiation on the earth. At present, ozone depletion is matter of concern because it causes various problems
in plants and animals. The harmful UV rays cause increased number of skin cancers, cataracts, reduced immunity
and mutations in humans and also affect photosynthesis in plants. To minimse the ozone depletion,
several developed as well as developing countries agreed to obey the steps being taken to limit the use of
CFCs and halons. Refer to text.
MULTIPLE CHOICE QUESTIONS
1. The effect of pollution is first and most marked on:
(A) natural flora of a place
(B) natural balance of our environment
(C) natural geochemical cycles
(D) all the above.
2. Ozone layer is destroyed due to :
(A) CFC
(B) CO2
(C) S02
(D) NH3.
3. Threat for the existence of human being is :
(A) low forest
(B) high population and pollution
(C) deforestation
(D) high population.
4. Air pollution is maximum caused by :
(A) household detergents and pesticides
(B) automobile exhausts and chemicals from industries
(C) sewage and pesticides
(D) sewage and industrial effluents.
5. Which of the following groups contain only biodegradable items ?
(A) grass, flowers, leather
(B) glass, wood, plastic
(C) fruit peels, cake, lime juice
(D) cake, wood, grass.
6. Which of the following constitute a food chain ?
(A) grass, wheat, mango
(B) grass, goat, human
(C) goat, cow, elephant
(D) grass, fish, goat.
7. Which of the followifng are environment friendly practices?
(A) Carrying cloth bags to put purchases in while shopping.
(B) Switching off unnecessary lights and fans.
(C) Walking to school instead of getting your mother to drop you on her scooter.
(D) All the above.
8. Which ofthe following is an omnivorous animal ?
(A) Deer
(B) Cat
(C) Lion
(D) Goat.
9. Which of the following is not .an abiotic component of ail ecosystem ?
(A) Plants
(B) Soil
(C) Air
(D) Sunlight.
10. Which of the following is a man made ecosystem?
(A) Pond
(B) Aquarium
(C) Lake
(D) Forest.
FILL IN THE BLANKS
1. Sunlight, temperature, rainfall, humidity are .............. factors of environment.
2. ......... of solar energy is fixed by plants.
3. ......... of energy is transferred from one trophic level to another.
4. Interconnected food chains form .......... .
5. Out of glass, D.D.T. and paper, the biodegradable waste is ..............
6. Out of wheat, cattle dung, aluminium foil and bagasse, the non-biodegradable waste is ............ .
7. Animals which feed on dead animals are called ............ .
MULTIPLE CHOICE QUESTIONS
1. B 2. A 3. B 4. B 5. C 6. B 7. D
8. B 9. A 10. B
FILL IN THE BLANKS
1. Abiotic 2. One per cent 3. 10 per cent 4. Food web
5. Paper 6. Aluminiumfoil 7. Scavengers
VERY SHORT ANSWER QUESTIONS
1. Name various components of environment.
2. Name two main abiotic factors which affect human environment.
3. What do you understand by the term ecological imbalance?
4. What do you understand by term sociocultural environment ?
5. Define biomagnification.
6. List the constituents of biotic environment.
7. What are ecological pyramids?
8. What are primary and secondary consumers ?
9. Expand UASB.
10. What do you understand by biological magnification ?
SHORT ANSWER QUESTlONS
1. What will happen if we kill all organisms in one trophic level ?
2. What are the problems caused by the nonbiodegradable wastes we generate ?
3. How recycling of waste materials help in ecological balance ?
4. Explain how ozone layer acts as our saviour ?
5. How can you make a balance between environment and development ?
LONG ANSWER QUESTIONS
1. In the food chain given below, grass provides 4000 J of energy to grasshopper.
How much energy will be available to snakes from frogs ?
Grass —® Grasshopper —® Frogs —® Snakes.
2. Explain why food chains with more than six food chains are rare.
1. Insectivorous plants grow only in soils deficient in :-
(A) calcium
(B) phosphorus
(C) nitrogen
(D) copper
2. Biomass produced by plants in oceans accounts for :-
(A) 85%
(B) 75%
(C) 65%
(D) 55%
3. Geothermal energy is :-
(A) non-renewable non-conventional energy source
(B) non-renewable conventional energy source
(C) renewable non-conventional energy source
(D) renewable conventional energy source
4. Inexhaustible, non-conventional source of energy is :-
(A) solar radiations
(B) wind power
(C) sea tides
(D) all the above
5. Soil is composed of :-
(A) mineral + water + air
(B) mineral + organic matter + air
(C) mineral + organic matter + air + water
(D) organic matter + water
6. Plants growing in extremely cold soils are :-
(A) halophytes
(B) psammophytes
(C) oxylophytes
(D) psychrophytes
7. Which one of the following animals can live from birth to
death without even drinking water :-
(A) Kangaroo rat
(B) Kangaroo
(C) Camel
(D) Desert cat
8. Energy and nutrients enter a community by way of the :-
(A) producers
(B) consumers
(C) detrivores
(D) scavengers
9. Which is the correct sequence in the food chain in grassland ?
(A) Grass ® wolf ® deer ® buffalo
(B) Grass ® insect ® bird ® snake
(C) Grass ® snake ® insect ® deer
(D) Bacteria ® grass ® rabbit ® wolf
10. There is no difference between the following :-
(A) primary consumers and herbivores
(B) trophic level I and herbivores
(C) primary carnivores and trophic level II
(D) Secondary consumers and herbivores
11. Driving force of ecosystem is :-
(A) carbohydrate in plants
(B) biomass
(C) solar energy
(D) producer
12. An aquatic plant with floating leaves :-
(A) have stomata on leaf surface
(B) have stomata on lower surface
(C) have stomata
(D) have stomata only on upper surface
13. Acid rain is caused due to increase in concentration of :-
(A) SO2 and NO2
(B) CO and CO2
(C) CO and SO3
(D) ozone and dust
14. Which is NOT a green house gas ?
(A) CO2
(B) H2
(C) CFC
(D) Methane
15. Lichens are important in the studies on atmospheric
pollution because they :-
(A) can also grow in greatly polluted atmosphere
(B) can readily multiply in polluted atmosphere
(C) are very sensitive to pollutants like SO2
(D) efficiently purify the atmosphere
16. The study of interrelationship between living organisms
and their environment is called
(A) phytogeography
(B) ecology
(C) phytosociology
(D) ecosystem
17. Abiotic component in an ecosystem is
(A) water
(B) daphnia
(C) bacteria
(D) chlorella
18. Who had proposed the term ecosystem?
(A) Gardner
(B) Tansley
(C) Odum
(D) Krebs
19.Which one of the following is the definition of ecosystem?
(A) A localised association of several plants and animals
(B) Different communities of plants, animals and microbes,
together with their physicochemical environments
(C) Different communities of plants and microbes, plus their
physicochemical environments
(D) A community of organisms interacting with one another
20. Good soil is
(A) which allows the limited amount of water into it
(B) which allows to percolate the water slowly form it
(C) which allows to pass water very quickly from it
(D) which holds whole of water into it
21. Humus is an example of
(A) crystalloids
(B) organic colloids
(C) soil structure
(D) none of them
22. Plants growing in shady regions are
(A) sciophytes
(B) xerophytes
(C) heliophytes
(D) epiphytes
23. Plants occurring on soils rich in salts are known as
(A) heliophytes
(B) halophytes
(C) geophytes
(D) thermophytes
24. Which of the following is the most characteristic feature
of a xeric environment?
(A) Low atmospheric humidity
(B) Extremes of temperature
(C) The precipitation
(D) High rate of vaporisation
25. Mechanical tissues are very poorly developed in :-
(A) xerophytes
(B) halophytes
(C) hydrophytes
(D) lithophytes
26. Xerophytes have long roots
(A) due to -light
(B) to draw water from deep water beds
(C) to give mechanical support
(D) none of the above
27. Mangrove plants show vivipary. This is
(A) germination of seeds within fruits while still attached to parent plant
(B) germination of seeds in fruits on the soil
(C) germination of seeds within fruit on sterile artificial culture medium
(D) germination of seeds only after dispersal of fruits
28. The orchid plants, which are found growing on the trees, are
(A) parasites
(B) epiphytes
(C) saprophytes
(D) lithophytes
29. In submerged hydrophytes functional stomata are found
(A) on lower surface of leaf
(B) on both the surface of leaf
(C) no where on the plant
(D) on upper surface of leaf
30. A food chain consists of
(A) producers and primary consumers
(B) producers, herbivores and carnivores
(C) producers, consumers and decomposers
(D) producers, carnivores and decomposers
31. Which of the following is the correct sequence in food chain?
(A) Fallen leaves ® bacteria ® insect larvae ® birds
(B) Phytoplankton ® zooplankton ® fish
(C) Grasses ® fox ® rabbit
(D) Grasses ® chameleon ® insects birds
32. Which is a primary consumer?
(A) Scavenger
(B) Saprophyte
(C) Carnivore
(D) Herbivore
33. Energy and nutrients enter a community by way of the
(A) producers
(B) consumers
(C) detrivores
(D) scavengers
34. When a big fish eats a small fish, which eats water fleas supported
by phytoplankton, the water fleas are
(A) primary consumers
(B) secondary consumers
(C) top consumer in this food chain
(D) producers
35. In natural ecosystem, decomposers include
(A) only microscopic animals
(B) only bacteria and fungi
(C) the above two types of organisms plus microscopic animals
(D) only the above two types of organisms
36. The food chain in which microorganisms break down the energy
rich compounds synthesised by producers is
(A) detritus food chain
(B) predator food chain
(C) consumer food chain
(D) parasitic food chain
37. In an aqueous environment, microscopic animals and plants are collectively known as
(A) herbivores
(B) fauna and flora
(C) planktons
(D) symbionts
38. Water logged soil is
(A) physically as well as physiologically dry
(B) physically wet but physiologically dry
(C) physically dry
(D) physically as well as physiologically wet
39. Carbon dioxide in atmospheric air amounts to about
(A) 0.03%
(B) 0.003%
(C) 0.3%
(D) 3%
40. The presence of ozone in the atmosphere of earth
(A) is advantageous since it supplies O2 for people travelling in jets
(B) helps in checking the penetration of ultraviolet rays to earth
(C) hinder higher rate of photosynthesis
(D) has been responsible for increasing the average global temperature in recent years
41. The term biodiversity refers to the
(A) Varitions in man
(B) A species found in a particular area
(C) Variety of different types of organism found on earth
(D) All of the above
42. Silent valley-which contains very rare species of plants and animals, is situated in
(A) Kerala
(B) Rajasthan
(C) Jammu and Kashmir
(D) Bombay
43. "Chipko Movement" is concerned with
(A) plant conservation
(B) project tiger
(C) animal breeding
(D) plant breeding
44. A biosphere in nature may be compared with a
(A) Bacteria
(B) Cell
(C) Nucleus
(D) Cell wall.
45. The biosphere includes
(A) Pedosphere (soil)
(B) Hydrosphere
(C) Atmosphere
(D) All of these
46. A natural forest is an example of
(A) Hydrosphere
(B) Biotic community
(C) Ecosystem
(D) All of these
47. The Sahara desert is an example of
(A) Population
(B) Biotic community
(C) Biosphere
(D) Biome
48. The 'producers' in general are
(A) Autotrophic animals
(B) Heterotrophic plants
(C) Heterotrophic animals
(D) Autotrophic plants
49. Man in everyday life produces food synthetically.
On the basis of this can man be called a producer?
(A) Yes
(B) No
(C) Insufficient information to answer
(D) Cannot be definitely said.
50. Suppose all consumers of the earth are dead. Then
(A) Producers will not prepare food
(B) Decomposers will die
(C) There will be no sunlight available by photosynthesis.
(D) None of these
51. Why does a goat not eat a tiger?
(A) Because the tiger is more powerful than the goat
(B) Because the goat is not adapted to eat flesh.
(C) Because every goat is taught by its parents to keep away from tigers.
(D) All of these
52. The correct food chain out of the following is
(A) Tiger ® Cat ® Lion ® Goat
(B) Grass ® Insects ® Lizard ® Snake
(C) Grass ® Rabbit ® Lion ® Man
(D) Sun ® Plant ® Insect ® Man
53. Many food chains form a
(A) Bigger food chain
(B) Food net
(C) Food space
(D) Food web
54. Following is an incomplete food chain:
Grass ® ? ® Jackal ® tiger. The choice for the correct answer will be
(A) Lion
(B) Deer
(C) Rat
(D) Cockroach
55. The loss of energy in successive steps of energy transfer is aproximately
(A) 20%
(B) 25%
(C) 10%
(D) 2%
56. Sahara desert has been formed by
(A) Disastrous climatic conditions
(B) Overgrazing of fields
(C) Uncontrolled industrialisation
(D) All of these
57. Environmental planning will
(A) reduce spoilage by bacteria
(B) cause more wildlife loss
(C) reduce air and water pollution
(D) None of these
58. Which industrial unit is held responsible for the harm to the Taj Mahal in Area?
(A) Indian Fertiliser Company
(B) Mathura Oil Refinery
(C) Madras Refineries Limited
(D) Nuchem Plastics Limited
59. An example of aerosol spray is
(A) Dichloro difluoro methane
(B) Tetra chloromethane
(C) Trichloro methane
(D) Di-iododibromo methane.
60. The full form of DDT is
(A) Dibromo Dichloro Toluene
(B) Dichloro Diphenyl Trichloroethane
(C) Difluorodichloro Terbutaline
(D) None of these
61.'Biological magnification' is related to
(A) Death of pelicans by DDT
(B) Overpopulation of trees
(C) Multiplication of bacteria
(D) Disposal of wastes
62. Lichens are found on hillsides under conditions where neither the alga nor
the fungus can live alone. This shows that the relationship between the
alga and the fungus is one of
(A) Parasitism
(B) Saprophytism
(C) Mutualism
(D) Commensalism
63. During the period when two species occupy the same ecological niche, they are
(A) Dependent on each other
(B) Competing with each other
(C) Cooperating with each other
(D) Not affected by each other.
64. Conservation of the ecosystem rather than conservation of a
particular species is important because
(A) Food chains and food webs are maintained
(B) Different cycles operate simultaneously
(C) Abiotic and biotic factors operate at a given place
(D) All of the above operate.
65. The top soil is darker and
(A) is drier than subsoil
(B) is richer in Na and Mg
(C) is wetter than subsoil
(D) contains more organic matter
66. Organic matter decayed to a relatively stable, amorphous state;
formed when soil microorganisms decompose animal and plant
material into elements usable by plants
(A) manure
(B) peat
(C) humus
(D) green manure
67. Sheet erosion is due to
(A) fast running rivers
(B) heavy rains
(C) occasional rains
(D) wind
68. Which is a renewable source?
(A) Water
(B) Coal
(C) Fuels
(D) Minerals
69. A non-renewable resource is
(A) forest
(B) coal
(C) water
(D) wild life
70. Minerals and metals are
(A) biodegradable resources
(B) renewable
(C) non-renewable
(D) inexhaustible
71. Soil fertility is reduced by
(A) crop rotation
(B) nitrogen fixing bacteria
(C) decaying organic matter
(D) intensive agriculture
72. Largest amount of freshwater is found in
(A) lakes and streams
(B) underground
(C) polar ice and glaciers
(D) river
73. Inexhaustible, non-conventional source of energy is
(A) solar radiations
(B) wind power
(C) sea tides
(D) all the above
74. Soil is composed of
(A) mineral + water + air
(B) mineral + organic matter + air
(C) mineral + organic matter + air + water
(D) organic matter + water
75. Soil erosion can be prevented by
(A) restricted human activity
(B) good plant cover
(C) checking movement of animals
(D) wind screen alone
76. The species, which are in danger of extinction, are referred to as
(A) endangered species
(B) vulnerable species
(C) threatened species
(D) rare species
77. A biotic community consists of a union of
(A) Populations
(B) Biomes
(C) Ecosystems
(D) Individuals
78. The sum of all individuals of a given area is called
(A) Ecosystem
(B) Biome
(C) Population
(D) Individual group
79. Living and non-living species are parts of
(A) Biotic community
(B) Population
(C) Ecosystem
(D) Atmosphere
80. Pollutant from motorcar exhaust that causes mental diseases is
(A) lead
(B) NO2
(C) SO2
(D) Hg
81. Minamata disease is a pollution-related disease, which results from
(A) release of human organic waste into drinking water
(B) accumulation of arsenic into atmosphere
(C) release of industrial waste mercury into fishing water
(D) oil spills into sea
82. World environment day is
(A) 5th June
(B) 28th February
(C) 5th August
(D) 28th April
83. Eutrophication leads to death of fish due to
(A) increased O2 content
(B) increased algae content
(C) decreased algae content
(D) decreased O2 content
84. The two great industrial tragedies namely, MIC and Chernobyl tragedies
respectively occurred where and at which time?
(A) Bhopal 1984, Ukraine 1990
(B) Bhopal 1984, Ukraine 1988
(C) Bhopal 1984, Ukraine 1986
(D) Bhopal 1986, Russia 1988
85. Ozone day is
(A) January 30
(B) December 25
(C) April 21
(D) September 16
86. Formation of ozone hole is maximum over
(A) India
(B) Africa
(C) Antarctica
(D) Europe
87. Thermal pollution is more prevalent near
(A) hot water springs
(B) coal based power plants
(C) temperate zones
(D) tropical zones
88. Acid rain is caused due to increase in concentration of
(A) SO2 and NO2
(B) CO and CO2
(C) CO and SO3
(D) Ozone and dust
89. Ozone depletion is caused by
(A) carbon dioxide
(B) CFCs
(C) CO
(D) SO2
90. Smog is a combination of
(A) fire and water
(B) smoke and fog
(C) water and smoke
(D) air and water
91. BOD of a pond is related to_______in per unit volume of water
(A) all the plants
(B) all the nektons
(C) all the microbes
(D) all the animals
92. NO2 vapours are harmful to the body because
(A) They produce allergy
(B) They produce respiratory problems
(C) They create blood clots
(D) None of these
93. Excessive contact with industrial silicon dioxide (SiO2)
would lead to the disease called
(A) Encephalitis
(B) Cretinism
(C) Silicosis
(D) Silaceous anaemia
94. Why is smoking injurious to health?
(A) It can casue pregnanacy problems in smoking mothers.
(B) It can cause large scale air pollution
(C) It can be responsible for a heart attack
(D) Both (A) and (B)
95.'Decibel' is a unit to measure
(A) Sound depth
(B) Sound intensity
(C) Sound wavelength
(D) All of these
96. Noise pollution can be prevented by
(A) Stopping the blowing of all horns
(B) Banning all commercial loudspeakers
(C) Strict vigilance on noise limit
(D) Cleaning sound emitting parts of automobiles.
97. An effective method to stop air pollution is
(A) Degradation of wastes causing air pollution
(B) Keeping the river water clean
(C) Keeping factories away from big cities.
(D) None of these
98. The Ganga purification project is controlled by
(A) Central Water Commission
(B) Union Public Service Commission
(C) Central Pollution Control Board
(D) Central Intelligence Agency.
99. Sunder Lal Bahuguna is associated with the
(A) Salt movement
(B) Green revolution
(C) Greenhouse effect
(D) Chipko movement.