Lecture Objective: Basic ideas of environment, basic concepts related to environmental perspective, man, society and environment, their inter relationship.

Environment

The word 'environment' is derived from the French word 'environ', which means 'to surround '.

Environment is the sum total of physical, chemical and biological factors, which act upon an organism or

an ecological community and determine its form and nature of survival.

Animate and inanimate objects together constitute the natural environment making even human beings a

part of the environment. Man is the most advanced of all living beings, and is considered to be a social animal.

Therefore, it can be said that man lives in a socio-cultural environment that either directly or indirectly

influence him. In consequence, human beings also change or modify the nature of environment to suit their

requirements. However, these changes are not always beneficial.

The environment never remains static for any living organism; we live in a state of dynamic equilibrium

with the environment. The organism thus has to make adjustments in response to the changes in one or more

environmental factors (temperature, humidity, pH, etc.), to be able to survive, grow, feed and reproduce.

This is also true for plants and animals.

Organisms differ widely in their response to environmental changes.

Some organisms are very sensitive to even the slightest environmental change, while others have the ability

to modulate their metabolic processes and cope with these changes. Species which could not cope with a

change in environment have either become extinct or are on the verge of extinction.

1.1 ECOLOGICAL FACTORS OF ENVIRONMENT

There are four main ecological factors that cause changes in environment. These are:

1. Topographic factorsTopographic factors refer to the physical factors and comprise of direction of mountain chains, plateaus, altitude, plains, lakes, rivers and sea level.

2. Climatic factors These include atmosphere, light, temperature, humidity, and rainfall.

3. Edaphic factors These consist of the lithosphere, i.e., soil and rocks.

4. Biotic factors The biotic factors include all living organisms that interact with each other and with the abiotic components. Environment can be divided into two categories.

CATEGORIES OF ENVIRONMENT

1.2.1 Natural Environment

Natural environment is not man-made and has resulted from the evolutionary process. In a natural environment the environmental system operates through a self regulating mechanism called 'homeostatic' mechanism.

In that mechanism, if any change is brought about in the natural environment by anyone component (air, water, soil, forest, etc.), it is counter-balanced by changes in some other component in order to maintain stability, i.e., equilibrium.

1.2.2 Man-made Environment

Man being the most advanced among all the animals, have the ability to modify the environment to a great extent with the help of various technologies. Man-made environment includes buildings, transport vehicles, power plants, and space labs.

1.3 COMPONENTS OF ENVIRONMENT

Environment comprise of four components or segments: I. Atmosphere: the sphere of air.

2. Hydrosphere: the sphere of water.

3. Lithosphere: the sphere of soil, rock etc.

4. Biosphere: the sphere of living organisms.

Environment

Atmosphere

The thick, gaseous blanket like of cover of air surrounding the earth is called atmosphere. It sustains life on earth by removing harmful cosmic and ultraviolet rays through absorption, maintaining heat balance, providing oxygen for respiration and carbon dioxide for photosynthesis.

On the basis of temperature gradients, the atmosphere can be segmented as follows:

(a) Troposphere (b) Stratosphere (c) Mesosphere (d) Thermosphere

(e) Magnetosphere.

Hydrosphere

Approximately seventy per cent (70%) of the earth's surface is made .up of, and constitutes, the hydrosphere.

The water resources include oceans, seas, rivers, lakes, streams, ponds, glaciers, polar ice caps and ground

water. Of this, about ninety-seven per cent (97%) of the water is salty and is present in oceans and seas, two

per cent (2%) is present as ice caps and the remaining one per cent (1%) as fresh water which we use

variously. Water near the poles is very cold and freezes to form polar ice caps, glaciers or icebergs. However,

at the equator, water evaporates into gas due to high temperature. The frozen water in its own sphere is known

as 'cryosphere'.

Water is very essential for life and it is believed that the first signs of life were found in water.

Lithosphere (Land)

Lithosphere is the solid component of earth. It consists of three layers: crust, mantle and core. Generally speaking, lithosphere means the hard surface (crust) of earth and not the entire inside of the planet. The uppermost part of the solid earth, consisting of weathered rocks, minerals and organic matters together, is known as soil.

Land is very important for use in agriculture, industrialization, transportation as well as recreation etc. The interior of the lithosphere consists of mantle followed by core.

Biosphere

It is that part of earth where living (biotic) organisms exist and interact with one another, as also with the non-living (abiotic) components. The living organisms include all of the micro-organisms, plants and animals. Biosphere reaches well into the other three spheres, although there are no permanent inhabitants in the atmosphere. Relative to the volume of the earth, the biosphere constitutes only the very thin surface layer, which extends from 11,000 meters below sea level to 15,000 meters above it.

In general, biosphere includes most of the hydrosphere as well as parts of lower atmosphere and upper lithosphere.

The biosphere contains large quantities of elements such as carbon, nitrogen and oxygen. Other essential

elements like phosphorus, calcium and potassium are present in smaller amounts.

Bulk of the functioning in the eco-system is based on the input of solar energy and there is continual recycling

of materials at the ecosystem and biosphere levels. For example, green plants use carbon-dioxide for

photosynthesis and release oxygen into the atmosphere, which is then inhaled by the animals for respiration

releasing carbon-dioxide.

In the biosphere, there exist interactions among the organisms. When an organism interacts with members of

its own kind, it is an intra-specific interaction like lionization and then aggregation, etc. On the other hand,

interaction between different species is known as inter-specific interaction like neutralism, competition and

prey-predator relationships. The interactions may be harmful or beneficial to the participants but are very

important for the survival, growth, reproduction and continuance of the species.

Lecture Objective: To provide a clear idea on definition of resource, types of resource, renewable, nonrenewable, potentially renewable, effect of excessive use vis-à-vis population growth, definition of pollutant and contaminant. Environmental impact assessment (EIA) and Mathematics of population growth and associated problems. Acid rain, toxic elements, particulates, noise pollution, air pollution and its effect on man. Overall methods for pollution prevention, environmental problems and sustainable development, components of environment.

1.4 RESOURCE

Resource is a means, which may or may not be material. It has specific functions and can be utilized to meet

the needs of individual and society as a whole, in a given space and time.

Resources can be natural, like, air, water and soil, or they can be human resource like population, or

cultural resource like knowledge.

The generation of such important resources is hampered by various resistances such as, natural resistance

like cyclone, flood, drought; human resistance like war, over or under population and cultural resistance like

superstition and religious fundamentalism. Although natural resistance cannot be controlled, the other two can

and should be prevented in order to safeguard existence.

Biome: The biotic and abiotic components of an environment are together known as the biome environment.

Resistance

A material or energy, which creates disturbance at the time of formation of resource, is called 'resistance', and

can be classified into three categories.

1. Natural resistance - such resistances comes from natural processes, e.g., cyclones, floods, droughts, etc.

2. Human resistance - such resistances are man-made and can be prevented through scientific and logical

measures, e.g., population increment or decrement, war, etc.

3. Cultural resistance - such resistances come from human society through some beliefs that may not be

logical and mainly caused due to illiteracy, e.g., superstitions.

Resource and resistance are inter-related as well as interdependent.

Neutral Stuff

There are many materials in the world that can neither be termed as resources nor resistances. These materials

are known as 'neutral stuff'.

The neutral stuff has functionality but no utility. For example, the materials available from Antarctica are

not utilized due to natural resistance, but if utilized can destroy ecological problems.

They can therefore be termed as neutral stuff because they cannot be utilized as a resource; but at the same

time they do not create any resistance in the formation of other resources.

Impact of Population Growth on Resources

Development and growth of population use up natural resources to a large extent. However, since these

resources are limited, they get depleted at an increasingly faster rate. This results in environmental degradation

causing ecological imbalance.

Resources can be classified as:

1. Renewable, or inexhaustible resources,

2. Non-renewable or exhaustible resources.

1.4.1 Renewable or Inexhaustible Resources

These resources may be those having a life-cycle. These can be replaced from time to time, such as plants and

animals, or those that do not have a life-cycle but can be recycled, for example water. Replaceable renewable

resources, such as plants and animals, if not managed properly, may not become available with the same

speed and become extinct soon. On the other hand, these inexhaustible resources that are hardly

affected by man's activities are abundantly available and expected to be so for millions of years.

Solar energy, wind energy, atomic energy etc., are examples of such kind.

The renewable resources are of two types: 1. Conventional types, such as water resources, plants, forests, crops, wild-life, aqua culture,

etc. 2. Non-conventional types, such as solar energy, wind energy, biogas, atomic energy, etc. The renewable resources can be mainly grouped under (1) Water resources (2) Energy

resources.

1.4.1.1 Conventional Type Resources

Water Water is essential for domestic use, for generation of electricity, irrigation, navigation and also for living organisms. Currently, a lot of underground water is being used mainly for agricultural purpose, creating enormous load on the eco-system. Sufficient care needs to be taken to manage age water efficiently. Water is a renewable resource as has a life-cycle, the hydrologic cycle, which should be properly maintained. However, due to large-scale deforestation the water cycle gets disturbed.

Forests as a Renewable Resource

Forests constitute 90 per cent of the global biomass. They are important as they regulate climatic conditions such as rainfall, humidity, temperature and protect soil from erosion. Forests provide timber, fruits, medicine

(medicinal plants); protect public health by absorbing contaminants of the environment and provide suitable habitats for a number of plant as well as animal species. But due to improper management, vast stretches of forests are lost every year. To compensate the loss of forest cover due to its diversion, aforestation should be done so that the net area under the forest cover remains the same. Only then forests act as a renewable resource.

Wildlife as a Renewable Resource

Wild animals provide us meat for food, skin for leather goods and are used for research as well as recreational purposes. Man has killed millions of wild animals only to show its supremacy. The indiscriminate cutting of woods too has resulted in the extinction of at least one mammal and bird species every year. In order to make wildlife a renewable resource, proper management and awareness among people is very important.

Livestock as a Renewable Resource

The livestock such as cattie, goats, buffaloes, sheep, horses, camels, as well as fowls, ducks and turkeys, provide meat, milk, eggs, skin, wool and also dung, which can be utilized as biogas and manure. Livestock can be utilized as renewable source only through proper management such as, their health care, proper breeding, and proper diet.

Aqua Culture as a Renewable Resource

Fish, crabs, prawns molasses, etc., are a very important resource of animal proteins for human beings. The food proteins of marine animals are generally obtained from fish. Marine resources are the Indian Ocean, Arabian Sea, Bay of Bengal, as well as numerous gulfs, rivers, lagoons, water lakes and other inland water resources. Fish is cultured in ponds, artificial enclosures and net pens by providing fertilizers like cow dung, domestic and agricultural waste and also animal excreta. The aqua culture production can be increased by using composite fish culture, i.e., using the surface, middle and bottom for feeding fish in the same pond, avoiding competition among them for food.

Energy

Although fossil fuels are non-renewable, they still form very slowly as compared to their consumption. Biomass although non-renewable can be made renewable by fuel-wood plantations. However, due to indiscriminate felling of trees, forests have depleted and fuel-wood has become scarce.

1.4.1.2 Non-conventional Type Resources Solar Energy The main source of energy for the biological world is solar energy. The readily available solar radiations, particularly in tropical countries, can be trapped and converted to electrical energy, using devices such as a photo-cell. Thu~, advanced researches for the development of efficient photovoltaic devices to harness solar energy must be carried out.

Wind Energy

Wind energy can be converted into electrical energy by developing suitable technology. The electrical energy or electricity can solve energy problems in small towns or villages to a large extent. A common example of this usage is windmills that convert wind energy into mechanical energy for raising water from wells and rivers to the ground surface.

Wave and Tidal Energy

In areas where rivers meet the sea, they experience waves and tides. This enables large amounts of electricity to be generated. Energy can also be generated by a natural or artificial water fall. The hydroelectric power thus generated turns a turbine fast, thereby generating electricity.

Geothermal Energy

Hot springs are the contributors of geothermal energy as t1~ey have a lot of steam. This steam can be utilized to run turbines in order to generate electricity.

Biogas

The huge amount of cattle dung can be utilized for biogas production, which in turn can be used for cooking and to generate electricity.

Atomic Energy

Radioactive elements are utilized to harness energy in the atomic reactors. The nuclear reactors produce an enormous amount of heat that is used to produce steam, which in turn is used to run turbines to generate electricity. Atomic energy is a very important source of energy. One kilogram of natural uranium (U238)

generates energy equal to that generated by 35,000 kg of coal, which shows its tremendous potential.

1.4.2 Non-renewable, or Exhaustible Resources These resources neither have a life-cycle nor can be recycled, for example, mineral deposits, soil, fossil fuels like coal and petrol once used cannot be regenerated and are exhaustible, as their deposits are limited. Some important non-renewable resources are:

Mineral Resources

Minerals are natural substances (organic and inorganic) that occur as ores in the earth's crust. Minerals like iron (Fe), copper (Cu), zinc (Zn), manganese (Mn) and aluminum (AI) are used as building materials for manufacturing automobiles, ships, rail tracks, etc.; as nutrients for plants and as components of glass as well as ceramics. Minerals like coal and petroleum are used as energy resources and various industries depend on them on a large scale. Minerals like uranium and thorium are very important for generation of atomic energy.

The world's oil deposits are located in south-west Asia.

Land Resources

Land is undoubtedly the most precious resource due to its diverse use. It is mainly used for agriculture, as also for housing, industry, roads, for keeping forests, for grazing animals. For agriculture, quality of the soil is the most important parameter. Land and soil are non-renewable resources. Soil stores water, thereby helping plants to grow providing us with food, fiber, medicines, etc. Population growth followed by rapid industrialization, utilization of land for agricultural and for housing, construction of offices, buildings and large-scale deforestation have put great degree of pressure on the land as well as soil. Thus, a serious thought must be given to protect this resource if we want to save our earth and survive for long.

Non-renewable Oceanic Resources

Below the sea-level, there are lots of minerals such as, cobalt (Co), nickel (Ni), copper (Cu), iron (Fe) etc., which exist in the form of sulfides and oxides of manganese (Mn203). These minerals as well as natural oil and

gas deposits are now exploited to a great extent.

1.5 ENVIRONMENTAL DEGRADATION

The alarming rate of population growth followed by the need for acquisition of quality life has put excessive pressure on all of the natural resources. In order to meet the basic needs, there is rapid deforestation, industrialization and unplanned urbanization. All these human activities along with some natural occurrences have modified and even transformed the basic components of the environment.

Some of these components have changed to such an extent that they cannot be set right by the self regulatory mechanism (homeostatic mechanism) of the environment. Consequently, the changed environmental conditions adversely affect the living organisms of the biosphere. Environmental degradation thus can be defined as, the overall lowering of environmental qualities due to the damages caused by both natural events and human activities in the basic structure of the environment at local, regional and global levels adversely affecting all living organisms, including man.

Environmental degradation has led to the destruction of the environmental stability and ecological balance.

Some of the natural events that cause environmental degradation are volcanic eruptions, tropical cyclones, earthquakes, lightning, faulting, forest fires, floods; and droughts.

Examples of the anthropogenic activities causing pollution and ultimate degradation of environment are nuclear explosions, deliberate forest fires, and release of toxic chemicals into the atmosphere.

1.6 ENVIRONMENTAL POLLUTION

The term pollution is derived from the Latin word pollutioneum meaning 'make dirty'. Rapid and unplanned industrialization, urbanization, deforestation cause the release of a variety of extraneous materials (inorganic, organic, biological or radiological) and energy into the environment in a continuous and uninterrupted manner. When the concentration of such materials exceeds the threshold limit, the environment becomes partially or totally unsuitable for living organisms. This is known as environmental pollution. The concentration of the extraneous materials becomes so high that the eco-system is unable to either neutralize or disperse it and it gets accumulated. Pollution can thus be defined as 'an undesirable change in physical, chemical and biological characteristics of air, water and soil due to anthropogenic activities, which may harmfully affect the life or create a potential health hazard to all living organisms in the biosphere'. The extraneous materials and energy that cause pollution are termed as 'pollutants'.

Sometimes the term 'contaminant' is used along with 'pollutant'. Whereas pollutants are generally considered as substances that occur in nature in greater amount than natural abundance, are caused by human activities and have a detrimental effect on all living organisms, e.g., Pb, Hg, NOx; contaminants are substances which do not occur naturally are released into the environment by human activities. They mayor may not have detrimental effect, e.g., MIC (methyl isocyanate CH 3":"N=C=O). A contaminant is considered to be a pollutant only when it has any detrimental effect.

1.6.1 Pollutants

A pollutant may be defined as 'anything living or non-living or any physical agent (e.g., heat, sound, etc.), that in its excess makes any part of the environment undesirable for survival.

Polluted air is undesirable for breathing, for photosynthesis by plants; polluted water is undesirable for drinking and for all uses in day-to-day life; polluted soil and land is undesirable for growing food for humans and fodder for animals. Excessive heat due to deliberate burning of forests as well as high pitched sound (noise), are also pollutants as they affect living organisms. Some substances which do not seem to be pollutants can also pollute, e.g., the fertilizers used in agriculture if used in large concentration can pollute lakes, rivers, ponds.

Pollutants can be the wastes of solid, liquid, gas as well as energy. Some of the examples can be cited as

below. Solid wastes: Garbage, rubbish, ashes, animal wastes, agricultural wastes, mercury, etc,

Liquid wastes: Organic liquids, inorganic acids, alkalis, etc. Gaseous wastes: Carbon monoxide, nitrogen dioxide, sulfur dioxide, ozone, etc.

Energy wastes: Heat, noise and radioactive wastes.

Some pollutants are bio-degradable whereas others are not. Some of the biodegradable pollutants are wastes of plants or animals and are generally organic substances. The non-biodegradable substances can be pesticides, heavy metals like lead, mercury and their salts, plastics, glasses, etc.

Some carcinogenic chemicalsDepending upon the nature of pollutants (solid, liquid, gas, energy) and the type of environment (air, water

and land); pollution can be classified into six major categories: (1) Air pollution, (2) Water pollution, (3) Land pollution, (4) Noise pollution, (5) Thermal pollution, and (6) Radiation pollution.

1.6.2 Effects of Pollution

Effects of pollution are numerous. However, some of the important ones are - pollution can bring about complex changes in the ecosystem; endanger aquatic life, cause dormant germs to get activated and spread unknown diseases endangering all living organisms, erode matter thereby shortening their lifespan, and speed up natural decay through synergism.

1.7 ENVIRONMENT MANAGEMENT

Although environmental degradation occurs through both natural processes and anthropogenic activities, the main culprits are human beings - because they have overexploited the limited natural resources. Environmental degradation and pollution in turn have caused a catastrophe affecting all the living organisms in the biosphere. Thus, there is an urgent need to protect the natural resources for our present as well as future generation.

Although it is a difficult job, it is not impossible but can only be tackled through a well planned strategy of environmental management.

The main objectives of environmental management are:

To restrict and regulate overexploitation of natural resources.

To protect the environment from degradation.

To maintain ecological balance.

To maintain environmental quality.

To renew natural resources with suitable devices.

To formulate and implement stringent laws and regulations.

The main components of environment management are:

Environmental education and train.ing.

Public awareness.

Control overpopulation and overconsumption.* Environmental impact assessment, to review the existing technology for better substitution.

1.8 ENVIRONMENTAL IMPACT ASSESSMENT (EIA)

The impact of anthropogenic activities on the use of environmental resources or the natural environment is termed as Environmental Impact. The assessments or evaluations of this impact are collectively called Environmental Impact Assessment (EIA).

EIA is required to understand the detrimental environmental changes like the degradation of environment, ecological imbalance, etc. and take proper measures to make the earth environmentally sound for our existence.

The ultimate objective of EIA is to provide information to the decision makers so that proper programs, plans can be made and new projects implemented. The EIA is very important as its results help to implement appropriate procedures or measures in the various countries keeping in view their national laws and processes related to decision-making, exchange of information and consultation.

The steps involved in the EIA study are: (i) Screening of the project

Which projects need EIA, or do not need it, are identified. (ii) Impact identification of the

project

The significant impact of the project is identified and if required, alternatives are suggested.

(iii) Impact prediction

The magnitude and duration of the impacts on the environment are predicted through various models, laboratory experiments and judgment by experts.

(iv) Impact evaluation

The impacts so predicted are scientifically evaluated by comparing the values against set standards.

(v) Participation of stakeholders

. For improving quality, comprehensiveness and effectiveness stakeholders' opinions are considered adequately. (vi) Specification of monitoring and auditing measures

Impacts that require continuous monitoring are identified and their auditing is undertaken.

(vii) Documentation of EIA study

Draft record along with non-technical summary containing the methodology; number of steps involved; results and discussions; interpretations and conclusions are prepared.

(viii) Review of report

Drawn up reports are reviewed by experts to evaluate the efficiency and quality of the EIA. Suggestions are made by the experts. If some items are missing, they are modified as required or accepted by the reviewers in order to facilitate the process of decision-making.

(ix) Decision-making

In the end, decision-makers decide the future prospects of the proposed project based on the comments and recommendations of the reviewers thought the EIA report.

1.9 POPULATION GROWTH

The term population originated from the Latin word populas, meaning people. In ecology, population is defined as a group of organism of a particular species, which breed among themselves or have the potential to do so and generally occupy a particular space. Population growth thus can be defined as 'the change in strength of population per unit area at a particular time'. The strength obviously varies from time to time as individuals are born, die or migrate from one place to another. The rate of increase of population depends upon the birth rate, death rate, immigration or emigration and all these factors in one way or the other are related to the ecological conditions.

Prediction or forecasting about future population is very essential as this can be helpful in proper designing of engineering constructions and more thorough scientific innovations. Short-term, short-time predictions, although beneficial, cannot be very helpful in the future. If the idea be concentrated on the growing demands of modem life facility, the remaining amount of fossil fuels, the rapidity of deforestation along with the prediction of future population growth, then a clear picture can be obtained and proper measures be taken. This is vital for maintaining the economic growth rate, innovating proper scientific methods and engineering construction so as to avail alternate energy sources without polluting the environment.

The simple but powerful mathematical tools thus developed are either exponential or logistic in function and can throw light on several environmental problems.

On the basis of mathematical functions, the population growth rates can be classified as:

Exponential growth

Logistic growth

1.9.1 Exponential Growth

In the case of exponential growth, the rate of change of population is directly proportional to the size of population at that time. If in a specified time 't', the population size be ' Nt' - then population growth or rate of change of population can be expressed mathematically as:

Doubling Time of Population

The time required for population to become double of its initial number (Nt) under consideration, that it grows exponentially and the growth rate remains constant throughout, is called 'Doubling time' (td).

We know that,

Nt = N0 eRt

Now if the growth rate R is expressed as a percentage in-stead of a fraction, then,

2No = NoeRtd

Or eRttd = 2 or IneRtd = In2

In2 0.693Or td= - = --

. R R

Now if the growth rate R is expressed as a percentage I n-stead of a fraction, then,

69.3 70 td = R (%) = R (%)

Thus, the length of time required to double a quantity growing at R. per cent is approximately equal to 70

divided by R per cent.

In case of non-continuous growth rate, i.e., when the growth rate remains constant for a certain period of time, the mathematical expression is as follows:

For No = initial size of population

Nt = size of population after time t

R = growth rate per year.

Then, Nt+1 = Nt + RNt = Nt (l + R)

When t = 0, N1 = No (1 + R);

For, t = 1, N2 = N1 (l + R) = No (l + R)(1 + R) = No (l + R)2 Thus the generalized form becomes, Nt = No

(l + R)t

Half life time of population

Now the generalized formula for exponential growth is Nt = N o e Rt . The time required for the population to become

half of it its present value when it decays exponentially, and the decay rate remains constant throughout is called

'half life' (t1/2)'

In the case of decay, the rate constant of growth and rate constant of decay may not be same; so the exponential decay will be,

Nt = Noe-R1

t

(- sign indicates decay and R1 represents the decay rate constant)

For time t to be t1l2,

Nt=N0/2

Or, N0/2 = Noe-R1

t1/2

½ = e-R1

t1/2

or, 2= eR1

t1/2

or, eR1

t1/2=ln2

or tl/2 = ln2/R1 = 0.693/R1 = 69.3/R1 (%) = 70/R1(%)

Under conditions of similar growth and decay rate (R =R1) the 'doubling time' and 'half life time' becomes equals. Validity of exponential growth The equation for doubling time is,

td = 70/ R(%)

Now, if we consider the growth rate to be 2 per cent, then if the population was 3 billion in 2000, it will become 6 billion by 2035, and if the growth rate remains stable at 2 per cent, then in doubling times i.e., in 140 years (by 2140) the population will become 48 billion. In 20 doubling times it will be in the order of quadrillion or more than one person per square foot of surface area on the earth. Such a large figure simply points out the limitations of mathematical formulation of exponential growth. Logically too, the growth of population must depend on the. availability of natural resources. With finite (limited) natural resources, a species cannot support any population beyond a certain limit. There always exists an upper limit to the number of individuals that an environment can support and is called the 'carrying capacity' of environment.

If exponential growth is assumed, what seems to be an abundant resource may actually be consumed very quickly thus making the fossil fuels and minerals extracted from the earth's crust to vanish rapidly. Considering the limitations of exponential growth ideas and related mathematical formulations, the population

projections are mathematically modeled with a logistic or S shaped (sigmoidal) growth curve.

1.9.2 Logistic Growth of Population

The sigmoidal growth curve can be separated into three segments, i.e., A-B; B-C ,and C-D. 1. A:-B: In this part, the population size N is much less than the environmental carrying capacity K and

under such circumstances:

N/K ≈ 0 ; dN/dt = rN or, dN/dt α N

Thus, in this region population grows exponentially and this is because the population is far below the environmental carrying capacity, therefore, the environment i~ highly suitable for its growth.

2. B-C: In this part, the population increment is relatively rapid compared to the first phase: This phase is

The shortcomings of the mathematical model for exponential growth are overcome by mathematical modeling with a logistic or S shaped (Sigmoidal) growth curve.

The logistic curve is derived from the following differential equation as proposed by Verhulst, a distinguished French mathematician.

dN =rN(I- N/K)dt

Where N is the population size, K is called the carrying capacity of the environment, and r is the logistic growth rate.

called the 10garith(l1ic phase. In this region, N is not much less than K and the population growth is steady, i. e.,

dN/dt = Constant.

3. C-D: In this part, the population growth decreases as N approaches K, i. e., (N-K) becomes smaller and smaller. When population size (N) becomes equivalent to the environmental carrying capacity (K), i.e.,

N=K , dN/dt =0 ,

The growth rate of population (r) becomes zero (zero population growth or ZPG). Population at point (D) is called the 'population at saturation value'.

An eco-system has limited resources. Therefore, if population grows beyond the carrying capacity of the eco-system, the resource limit shows an adverse effect on population by increasing death rates or reducing birth rates. Such resistance as offered by the environment is called 'environmental resistance' or 'growth realization factor'. This factor (1- NIK) is called environmental resistance. Thus, if N becomes greater than K (N > K); (l – N/K) becomes negative, and hence,

dn/dt = -ve

This factor (1- N/K) is responsible for changing the 'exponential growth curve' into 'logistic growth curve'.

Logistic growth rate constant (r)

We know, dN = rN (1-N/K) …………………….(1)dt

where r is the logistic growth rate constant, N is the population size and K is the carrying capacity of environment.

Rearranging equation (1) we get,

dN / N (1-N/K) = rdt

Now, 1/ N (1-N/K) = 1/ N {(K-N/K)}= K/N(K-N)

dN/N(1-N/K) = rdt

Hence, dN [1/N – 1/(N-K)]= rdt ….(2)

Now if we consider that at time 't', population is N and at time' t' , population is equal to half of the carrying capacity (K), i.e., (K/2), which is constant under a given environmental condition, then integrating equation (2) in the limit of N to K/2 and t to t* will give,

K/2∫N dN[1/N – 1/(N-K)]= t*∫t rdt = r t*∫tdtK/2∫N dN/N- K/2∫N dN/(N-K)= r t*∫t dt

1.9.3 Maximum Sustainable Yield

Maximum sustainable yield means the maximum rate at which individuals of an ecosystem can be harvested

(removed) without reducing the population size. For example, suppose we want to harvest chicken in a poultry

farm. If the farm is at its carrying capacity, there will be no population growth, and hence removal of any

chicken will automatically reduce its population. Therefore, the maximum sustainable yield will correspond to

a population size less than the carrying capacity.

1.10 HUMAN POPULATION DYNAMICS (DEMOGRAPHY)

The logistic growth equations can predict with some degree of accuracy the density dependent population, but not the human population growth. The very important study of human population dynamics is known as 'demography' and it deals with the fertility as well as mortality rates and population age composition. The three important parameters that come under demography are:

1. Total Fertility Rate

2. Mortality Rate

3. Age Structure of Population.

Total Fertility Rate (TFR)

Total fertility rate (TFR), is the average number of children that will be born alive to a woman in her life time. Averages are made because all women cannot have equal number of children; some can have more and some less. .

Theoretically, when TFR = 2, each pair of parents just replaces themselves, and when it exceeds 2, then there is a replacement of each generation. In developed countries, TFR values lies around 1.6, in less developed countries the 'value is about 3.5, and in poorest countries it may be over 7.0. The number of children that a woman must have, on the average, to replace herself with one daughter in the next generation is called 'replacement level fertility'. In developed countries the value is nearly about 2.11 and in many developing countries it may be 2.7.

Even if the replacement level fertility is achieved, population growth can continue. The continuation of population growth, despite achievement of replacement level fertility, is a phenomenon known as population momentum.

Mortality Rate

An important measure of mortality is the infant mortality rate, which is the number of deaths to infants (under one year of age) per 1000 live births, in a given year.

The difference between crude birth rate (b) and crude death rate (d) is known as the rate (r) of natural increase of population.

r=b-d

If migration be considered, then

r=b-d+m

where 'm' is the net migration rate.

In developed countries the fall in birth rate is equivalent to that in the death rate. In developing countries, although the birth rate has not fallen fast, there is a fall in death rate due to medicines and better control of diseases. The rapid population growth on a global scale is due to the insignificant drop in birth rate in most developing countries.

Age Structure or Population Pyramid

Age structure or population pyramid is the graphical representation of data indicating either number of people or their percentage in each age group. An age structure diagram reflects a country's population trends and tells about both the recent past as well as the near future.

A stable population is one where the shape of the age structure is unchanging. When a population is both stable and unchanging in size, it is called a 'stationary population' . It can be concluded that age structure. or population pyramid-makers are aware of the birthrates, child mortality, mortality rates and life expectancy.

1.11 SUSTAINABLE DEVELOPMENT

Sustainable development is the development that meets the needs of the present without jeopardizing the needs of future generations.

. In other words, every generation should leave air, water and soil resources as pure and unpolluted. Although it is a difficult proposition, it can be achieved through proper environmental management.

Sustainable development has three important interdependent components:

(i) Economic development: Utilization of natural resources for cultivation, industrialization, creating job opportunities, raising quality of life.

(ii) Social development: Providing basic needs like food, clothes, shelter, health, education, etc.

(iii) Environmental protection: Providing clean water, air, soil, i.e., safe environment to present as well as future generations.

Human civilization through their excellence in scientific and technological fie Ids has reached a level enabling them to produce more of their own kind by cloning, exploit lands of other planets and receive information from any part of the world. However, at the same time the civilization is facing the greatest challenge for survival due to the catastrophe created through environmental degradation.

To meet the basic requirements of ever increasing population, industrialization is a must, but it results in pollution, environmental degradation and causes ecological imbalance. At the same time, industrial development cannot be sacrificed as it creates job opportunities, raises the standard of living and solves unemployment problems. In view of this, a balance has to be struck so that development and environmental protection occur simultaneously. To achieve this goal, sustainable development is the only answer. Development can be done if the following' concepts are taken care of.

* Reduction in excessive usage of resources and enhancing resource conservation, i. e., continuous use of renewable resources and protection of non-renewable resources from wastage and rapid depletion.

* Recycling and reuse of materials for waste minimization.

* Scientific management of renewable resources, especially bioresearches, which have a life-cycle and inherent sustainable qualities.

However, without proper social and economic development, sustainable development can not be achieved. In order to do so, we will have to eradicate poverty through almost equal distribution of resources, support social justice and equality.

Solved Examples:

1. The human population follows a logistic growth rate until it stabilizes at 10 billion. In the

year 1970 the world population was 2 billion with growth rate of 2.0%. When will the

population reach 6 billion?

Ans. We know that,

r = Ro / (1- No/K)

Hence, r = 0.02 / 1-2/10

= 0.025

The logistic growth rate of population is 0.025.

The time taken to reach 5 billion i.e. half of the carrying capacity or, final population size

will be,

t*= 1 / r ln (K/No-1) = 1 / 0.025 ln (10/2 -1) = 56 years.

( where, t* is the time period required to become half of the carrying capacity (K/2),

No = population at time (t) = 0 and K = carrying capacity.)

We know that,

N = K / (1+ e–r(t-t*) )

Or, t = 56- 1/ 0.025 ln (10/6 -1) = 72 years.

Hence, after 72 years the population would be 6 billion.

MCQ (Each question carries 1 mark)

1. Hydrosphere consists of

a. Air layers b. Rocks c. Soil d. Various water bodies and oceans

2. Which one is a primary pollutant

a. Smoke b. CO c. PAN d. CO2

3. Which one of the following is a renewable energy source

a. Thermal b. Hydroelectric c. Nuclear d. Solar

4. The maximum quantity of fresh water occurs in

a. Rivers b. Ground water c. Polar ice caps and glaciers

d. None of these

5. Which one is a green house gas

a.O2 b. N2 c.CO2 d. SO2

Short answer type questions ( Each carry 3 marks)

1. Write a short note on EIA.

2. Define environment and mention its different components.

3. Distinguish between pollutant and contaminant.

4. Differentiate between primary pollutant and secondary pollutant.

5. Briefly mention different aspects of non-renewable sources.

Short answer type questions ( Each carry 5 marks)

1. Define environment. What do you understand by environmental pollution? Give an

example.

2. ‘CO2 , a non- pollutant, is perhaps the single most important environmental problem

facing us at present’- Explain in terms of greenhouse effect.

3. Acid rain is caused by human activities- justify.

ECOLOGY

Ecology is a branch of science that deals with the inter-relationship between biotic (living) and abiotic (non-living) components of nature as well as with the relationship among the individuals, population and community of the biotic components.

The term 'ecology' is derived from two Greek words oikos (meaning house) and logos (meaning study of) and is used to denote the relationship between the organisms and their environment.

Ecology has been defined in a number of ways. According to Woodbury (1954), 'Ecology is a science which investigates organisms in relation to their environment' E.P. Odum (1969) defined ecology as 'the study of structure and function of nature'. The most acceptable definition of ecology was proposed by Charles Krebs (1985), Ecology is the scientific study of the interaction that determines the distribution and abundance of organisms.

In ecology, the term 'habitat' is used to denote the place where an organism's or species' population lives, for example pond. A pond is the habitat of zooplankton, fish. 'Niche' is the fundamental unit of an organism's or species' population in the community. Whereas 'habitat' is the place where an organism lives, 'niche' is the activity (functional) aspect of the organism. 'Population' is used to denote groups of individuals of anyone kind of organism and 'community' or biotic community includes all the populations of a given area, called habitat.

Ecology plays a significant role in our day to day life. It is concerned with agriculture, horticulture, as well as conservation of soil, forest, wildlife, water resources, etc.

OBJECTIVE OF ECOLOGY

The importance of ecology is due to the presence of man in the ecosystem. Man interacts not only with its own species but also with other living organisms. There are millions and millions of organisms dynaroic co-existence with each other and each one of them plays a significant role in the eco-system. Ecology thus has broad objective and provides a scientific basis for the aims of environmentalism, as well as for evaluating its goals and policies. Ecology does not dictate what is 'right' or 'wrong' but provides knowledge about the quantification of biodiversity and population dynamics. The main objective of ecology is to understand and take proper measures if and when required.

I. The local and geographical distribution and abundance of organisms.

2. The inter-relationship between organisms in population and communities.

3. The structural adaptations and functional adjustment of organisms to their physical environment.

4. The behavior of organisms under natural conditions.

5. The biological productivity of nature and its relationship with mankind.

6. Temporal changes in the occurrence, abundance and activities of organisms.

7. Conservation and management of natural resources and pollution.

2.2 CLASSIFICATION OF ECOLOGY

Ecology is a broad discipline comprising of many sub-disciplines. A common, broad classification, going from the lowest to the highest complexity, where complexity can be defined as the number of entities and processes in the system under study, is:

Physiological Ecology (Eco-physiology) and Behavioral Ecology. This ecology examines adaptations of an individual to his environment.

Population Ecology (or auto-ecology): This ecology studies the dynamics of population of a single species.

Community Ecology (or ~ynecology): This ecology deals with the interactions between species within an ecological community.

Eco-system Ecology: This ecology studies the flows of energy and matter through the biotic and abiotic components of ecosystems.

Landscape Ecology: This ecology examines the processes occurring in multiple eco-systems or very large geographic areas, as well as the relationship between the processes.

Ecology, however, can also be sub-divided into many other branches such as:

Animal ecology, plant ecology, insect ecology, desert ecology, pedology, palaeo ecology, ethology, space ecology and so on.

2.3 ECOLOGICAL FACTORS

In an eco-system, a Jiving organism is influenced by a large number of environmental factors. These environmental factors are known as ecological factors or eco-factors.

These factors may be biotic (living) or abiotic (non-living). All the environmental factors bring marked distributional, structural and functional changes in organisms. To live, grow and carry out all its activities, an organism requires a harmonious relationship with its immediate environment. The differences in vegetation of a desert and a rain forest, fish in sweet water and saline water, animals in tropical countries and cold countries clearly indicates the role of environmental factors in the distribution and survival of organisms in different eco-systems.

The organisms subjected to diurnal, seasonal, annual and cyclic relations of the environment, develop strategies to cope with these changes for their survival. Only those which are able to cope with the conditions remain, and those who cannot, become extinct.

The ecological factors can be classified into:

1. Climatic factors: (a) light (b) temperature (c) nature (d) rainfall (e) wind (f) humidity (g) atmospheric gases (h) pH A variation in these factors affects the distribution and lifestyle of organisms.

2. Topographic/actors: (a) Altitude (b) slope and direction of mountain chain and valleys.

3. Edaphic factors: Structure, formation and characteristics of different types of soils. Biotic factors: Biotic factors are derived from the interactions between different species of life (intra-specific as well as inter- specific). The different species mentioned here are plants, microorganisms and

animals.

S. Limiting factors.

2.3.1 Climatic Factors Light

Light plays a vital role for both plants and animals. Sunlight is the ultimate source of energy for the biological world. Light is highly essential for photosynthesis, plays important role in respiration and transpiration, regulates hormones in plants thereby modifying the shape and size, and influences the growth and development of flowers, fruits, germination and distribution of plants.

As far as animals are concerned, light influences reproduction and metabolism.

Heat

Like light, energy (heat) exerts a profound influence on the physiological and biochemical activities of organisms. Generally, organisms prefer to conduct their activities in a temperature region of 4°C. to 45°C. The physiological effects of temperature are the mineral absorption in plants, water uptake, growth, germination in plants and distribution, migration, hibernation and reproductive activities in animals. Both organisms exhibit morphological, ecological and physiological adaptation to the variation in temperature. The biochemical effects are due to enzymes and hormonal changes and are related to the temperature.

Water

Water is one of the most important materials necessary for life. All the physiological processes take place in water. The availability of water in an eco-system affects the distribution, growth and other activities of its organisms.

Rainfall

Rainfall (precipitation) determines the types of vegetation in any region. The evergreen forest in tropical regions is due to heavy rainfall throughout the year. The grasslands are found in regions where there is heavy rainfall in summer and low rainfall in winter. Due to changes in vegetation, the animals and birds also differ in the various regions.

Wind

Wind brings physical, anatomical and physiological changes to plants. Excessive transpiration due to wind leads to desiccation and death of apical mersi stems. Thus the plants become dwarf, contain small leaves and more branches. On the mountains, due to the danger of uprooting, the vegetation is composed of species having prostrate growth, with long underground root. This is known as growth of rhizome type.

Humidity

The physiological activities of organisms, like transpiration, absorption of water, etc., are greatly influenced by humidity. Thus, humidity plays an important role in the life of plants and animals.

Atmospheric Gases

Gases like nitrogen, oxygen, carbon dioxide, water vapor, (inert gases) are essential for sustaining life. However, gases like sulfur dioxide (S02)' Nitrogen dioxide (N02) hydrogen sulphide (H2S), and smoke particles from the industries have a major influence on the environment and lead to various physiological changes in plants and animals.

pH

pH can be deciding factor in aquatic eco-system, as far as distribution of organisms is concerned. For aquatic animals as well as for organisms . on land, the pH should not be too acidic or too alkaline. For every species, there is an optimum pH level where they can survive.

Large scale industrialization and the discharge of effluents into water bodies or the soil, change the pH level to a great extent, endangering the lives of organisms.

2.3.2 Topographic Factors

The physical geographical factors ~re known as topographic factors. These factors include (1) altitude (2) slope and (3) direction of mountain chains and valleys. All these factors affect the climatic conditions of a place, and thereby influence the distribution of organisms. With rise in altitude, there is progressive fall in temperature and as we go higher up with a decrease in temperature there is greater activity of the wind. A decrease in soil temperature reduces the absorption of water and nutrients by the plants. In higher altitudes, the atmospheric pressure, as well as decreased concentration of oxygen affects animals, particularly mammals. The slope and direction of mountain chains have a pronounced effect on the amount of solar radiation, rainfall, wind velocity, temperature and as a whole, the climate of the area. This in turn affects vegetation patterns and thus, the distribution of animals.

2.3.3 Edaphic Factors

Edaphic factors deal with the structure formation and characteristics of different types of soils.

Soil provides mechanical anchorage to plants and holds water and mineral ions for the plants. They provide a basis for the activities of micro organisms and animals. Soil contains organic and inorganic colloids, electrolytes, organic matter and soil organism. Soil water forms the life line of soil organisms; good growth of micro-organisms and soil invertebrate population occurs in soil containing adequate moisture. Water is a solvent for the organic nutrients as well as minerals and thus, its contents regulate the physiological,

morphological and anatomical features of plants.

Soil air, found in soil pores contains COz, 0Z' and Nz and their quantity differs from soil to soil. The soil air is a very important edaphic factor that determines the types of micro-organisms, soil animals and vegetation that grows in the soil. Similar to soil water it also brings about morphological, physiological and anatomical changes in plants and animals.

Soil temperature is very important as it affects the growth of micro organisms, plants and animals. The soil temperature influences root growth, the ability of the roots to absorb nutrients and movement of organism.

Soil pH and salinity is also important because when the pH of the soil is very high (highly alkaline) there is no vegetation.

Soil organism like bacteria, fungi and algae and animals like protozoa, nematodes, earthworms, modify the soil structure, increase soil fertility, and help to form humus. Nitrogen fixing bacteria and blue green algae fix atmospheric nitrogen and increase soil fertility.

Thus a change in any of the soil constituents will have a tremendous effect on the whole.

2.3.4 Biotic Factors

Organisms in the environment interact among themselves and this may be intra-specific (between populations of same organism) or inter-specific (between populations of different species). Some of the interactions are mutually beneficial; some are beneficial to only one species without harming the others or by harming the others. These interactions put together~, are referred to as 'biotic factors'. The biotic factors thus are:

Symbiosis

In symbiosis two different species depend metabolically upon each other and thus are mutually benefitted. The species are known as 'symbioses'. For example, Rhizobium bacteria and leguminous roots are the symbioses. In this case, the bacteria get protective space to live in and derive readymade food from 'leguminous roots. The leguminous roots on the other hand, utilize the fixed nitrogen in the bacteria to manufacture proteins.

Commensalism

In this case, one species is benefited while the other either benefits or remains neutral. The members are called the 'commensals' and this association, is known as commensalism. For example, some algae and fungi join together, to form a different life form known as lichens. The algae manufacture food through photosynthesis, which the fungi utilize and in turn, the fungi protects the algae from drying up and together both colonize tree barks, rocks, etc.

Some terrestrial insects and marine animals share the nest or burrow of others without causing any damage to it.

Parasitism

In this case, there are two different species, i.e., one is the parasite and other h9st. Although the parasite is

benefited the host is harmed. The two different species may be two plants or animals. For example mosquitoes, bedbugs, lice are the parasites, which live on hosts like animal and man, harming them.

Epipllytism

In this case, epiphyte grows on other plants but do not derive food from them. For example, Lianas, a woody plant has roots in the ground but takes the support of other plants to climb.

Some carnivorous plants like, Nepenthes, a pitcher plant, grows on other plants but derives food from insects. They have folded leaf lamina modified into a pitcher like structure with a lid. Zooplankton enters into the structure through the lid, get trapped and the soft parts are digested.

Competition

Organisms survive on some materials and if these are found inadequate, competition occurs. The competition may be both intra-specific and inter-specific. This leads to the survival or dominance of certain species over others. As all the species cannot tolerate same range of temperature, humidity, etc., only those who can; survive.

2.3.5 Limiting Factors

Limiting factors denote the amount of substance that is either least abundant or overabundant in relation to the need of the living organism. Limiting factors may be density dependent, for example, when the food stock is fixed for a given density of population, overpopulation will lead to scarcity of food.

Limiting factor may be density independent, for example, earthquake or tsunami may wipe out an entire population irrespective of whether there are few or many. The density independent limiting factors affecting living organisms may be abiotic factors like climate, soil, wind, temperature, water, etc., or other biotic factors. Some climatic conditions may not be tolerable to certain species and might reduce their population or in extreme cases make them extinct. If the soil does not have proper amount of nutrients, air and moisture, the plants will not prepare balanced and sufficient amount of food to support animal life, reducing their population. Biotic factors are the most important limiting factors that influence the growth and distribution of plants and animals.

Laws of Limiting Factors

To explain the effect of different limiting factors on living organisms, a number of laws and principles are proposed by different scientists:

1. Liebig's Law of Minimum

An organism requires minimum quantity of a particular nutrient for its proper growth and if it is depicted below the critical minimum level, the organism will fail to grow or will grow abnormally.

For example, if the soil is deficient in anyone nutrient, it will make the other nutrient metabolically inactive and the proper growth of the plant gets restricted.

2. Blackman ~ Law of Limiting Factor

A biological process is controlled by a number of factors and the deficiency of any of these factors will affect the process as a whole. For example, photosynthesis by plants. Photosynthesis is dependent on right amount of water, carbon dioxide, chlorophyll,· intensity of solar radiation and temperature of chloroplast deficiency of any of these factors will affect the rate of photosynthesis.

3. Shelford~ Law of Tolerance

The law states that, it is not only that the minimum amount of a material can be a limiting factor, but also the excess amount of the same material can be limiting to the growth and development of an organism.

For example, all the soil nutrients are equally important for the growth and development of plants, but anything in excess might limit the uptake of the other nutrient, restricting the proper growth.

Every organism thus has an ecological minimum and maximum for every. factor and the range between two limits are known as limits or zone of tolerance. Thus, every environmental factor has two zones:

(a) Zone of tolerance, (b) Zone of intolerance

(a) Zone of tolerance.

This zone is favorable for the growth and development of organism. Zone of tolerance can be sub-divided into the following:

(i) Optimum zone: It is the most favorable zone for growth and development of an organism.

(ii) Critical minimum zone: It is the lowest minimum limit below which growth and development of the organism ceases.

(iii) Critical maximum zone: It is the highest maximum limit above which growth and development of the organism ceases.

(b) Zone of intolerance

Tolerance with respect to various factors differs from species to species. Organisms that have a wide range of tolerance for all factors have a better chance of survival and hence are widely distributed.

2.4 ECOLOGICAL BALANCE, OR ECO-SYSTEM STABILITY

Ecological balance or ecosystem stability implies a balance between . the production and consumption of each component in the ecosystem.

According to T.D. Brock, 'Steady state condition in nature eco-system is a time independent condition in which production and consumption of each constituent in the system is exactly balanced, the concentration of all constituents within the system remains constant, even though there occurs a continual change' .

There are a number of theories, mechanisms and models to explain the stability of eco-system. The important ones are:

(I) Theory of Diversity or Stability

If there is diversity of food webs it will lead to an increase in number of links in the food web and if community succession operates in an ecosystem, the stability will increase.

(il) Homeostatic Mechanism

Inbuilt, self-regulating mechanism is known as homeostatic mechanism. Ifni an eco-system the population of species increases significantly the result will be scarcity of food, leading to competition for food. Most species will die of starvation and the species population will be brought back to its original value and the stability will be restored.

(iil) Models

The equilibrium, as well as non-equilibrium model can explain stability. Thus, if the eco-system is disturbed by external factors, it may quickly return to its original state by some adjustment, restoring the stability. However, if it does not return to its original state, the disordered arrangement might lead to cross-relationships and make the system stable.

2.5 ECOLOGICAL INSTABILITY

When an eco-system is unable to adjust to the environmental changes, it is said to be unstable. The instability occurs due to a number of natural and anthropogenic activities such as destruction of natural vegetation or/and animal species, partly or completely, or by replacing them by other vegetations or/and animals; introduction of toxic substances like insecticides and pesticides and toxic gases like S02' N02, etc.

2.6 IMPORTANCE OF ECOLOGY

During the past decades, due to rapid increase in technology and population, humans have far more influence on their own environment than any other eco-system engineer.

Some quoted examples of ecological crisis are:

* Permian: Triassic extinction ever 25 million person ago

* Cretaceous: Tertiary extinction over 65 million years ago.

* Global warming related to green house effect naming could involve flooding of the Asian deltas, multiplication of extreme weather phenomena and changes in the nature and quality of the food resources.

* Ozone layer hole issue.

* Deforestation and desertification, resulting in disappearance of many species.

* The nuclear meltdown at Chernobyl in 1986 caused the death of many people and animals by cancer and caused mutation in a large number of people and animals.

The study of ecology helps us to understand the various primitives responsible for the existence of life on earth. The survival and wellbeing depend entirely on the ecological relationships. Although ecology is considered a branch of biology, ecology deals with many other branches of science such as chemistry, physics, geology, geography, meteorology, pedology, etc. Thus study of ecology gives a reactive insight into the universe and helps to take proper care of the environment for overall survival.

EXERCISES

Q. 1. What is ecology? Discuss in detail the scope and objective of ecology. Q. 2. What are the topographic ecological factors? Discuss the effects of light and temperatures on living organism.

Q. 3. Write notes on:

(a) Zone of tolerance and intolerance. (b) Light as a climatic factor.

(c) Edaphic factors as eco-factors. Q. 4. Why is the concept of limiting factors so important? Discuss Liebig's law and Blackman's law in this context.

Q. 5. Which ecological factors are most important and why? In what way are symbiosis and commensalisms different? How does altitude affects the distribution of animals?