Environmental Science

First Edition, 2009

ISBN 978 93 80168 58 6

© All rights reserved.

Published by:

Global Media

1819, Bhagirath Palace,

Chandni Chowk, Delhi-110 006

Email: [email protected]

Table of Contents

1. Basic System

2. Evolution and Development

3. Fundamental Issues

4. Problem of Pollution

5. Population on Rise

6. The Animals

7. Planet of Earth

8. The Forestry

9. The Settlements

10. Educational Aspects

11. Value of Learning

12. Learning Programme

13. Evaluation Process

14. Technological Aspects

15. National Concerns

16. International Concerns

1

Basic System

The term ecosystem was introduced by A.G. Tansley in 1935.

Before him, Mobins had used the term biocoenosis while Forbes

coined the term Microcosm for the community of the organisms.

Sukachev employed the term biogeocoenosis as synonym of

ecosystem.

“Ecosystem is a segment of nature consisting of community

of living beings and the physical environment, both interacting and

exchanging material between them.”

According to Evans “the ecosystem involves the circulation,

transformation and accumulation of energy and matter through the

medium of living organisms and their activities.

According to Fitzpatrick a group of organisms interacting among

themselves and with environment is known as ecosystem.

An ecosystem may be small like a drop of pond water (micro

ecosystem) or may be as large as ocean. Each ecosystem has

a distinct community with a distinct environment. Therefore, different

ecosystems are identified by their bionics e.g., freshwater

ecosystem, marine ecosystem, desert ecosystem, grassland

ecosystem, tropical ecosystem. However, these ecosystems are

not isolated. All the ecosystems of the world are inter-related and

exchange materials amongst themselves. Therefore, some workers

2 Environmental Science

consider the whole earth as ecosystem and call it biosphere or

ecosphere.

The Significance

1. Ecosystem study gives information about the amount of

available solar energy in an area.

2. It gives data about the availability of mineral elements,

their utilisation and recycling.

3. Inter relationships between various types of organisms as

well as between organisms and abiotic environment can

be known.

4. Productivity of producers and consumers is known.

5. The maximum number of producers and consumers of

various categories which can be supported in the

ecosystem is known.

Main Features

(i) The ecosystem is a unit of organisms connected to one

another and to their environment within given space and

time limit.

(ii) Any system composed of physical, chemical and biological

processes within a space and time unit.

(iii) It is composed of three basic components-biotic (biome),

abiotic (habitat) and energy components.

(iv) It occupies certain well defined area on the earth-space

and time unit.

(v) Ecosystem of any given space-time-unit represents the

sum of all living organisms and physical environment.

(vi) It is an open system which is characterised by continuous

input and output of matter and energy.

(vii) There are complex sets of interactions between biotic and

abiotic components including energy components on the

one hand and among the organism on the other hand.

(viii) It is powered by energy of various sorts but the solar

energy is the most significant and tends to be relatively

stable equilibrium. It has the natural resource system.

Basic System 3

(ix) It is well organised and structured system. The study of

ecosystem development is helpful in the environmental

planning from ecological point of view.

Different Varieties

Ecosystem can be natural or artificial, large or small, permanent

or temporary, complete or incomplete.

Natural Ecosystem : It is an ecosystem developed under

natural conditions without any major interference by man and

based upon the particular kind of habitat, these are further divided

into two sub categories.

(a) Terrestrial ecosystem, e.g., forest, desert, grassland etc.

(b) Aquatic ecosystem, e.g. freshwater lake, pond, river, sea.

Artificial Ecosystem (man-engineered) : It is an ecosystem

which is created and maintained by human beings, e.g., garden,

orchard, crop jand, aquarium, dam, village, town, city, piggery,

poultry etc. Agro ecosystem is the single largest man-made

ecosystem which has large number of variations.

Macro Ecosystem : A large ecosystem such as ocean, forest

etc.

Micro Ecosystem : A small specific part of a large eco-system

with its own specialisation e.g., sub-alpine ecosystem, valley

ecosystem.

Temporary Ecosystem : An ecosystem which persists for

only a short duration like rain water pond.

Permanent Ecosystem : Which persists throughout e.g.,

forest or a lake.

Incomplete Ecosystem : Which lacks one or the other

component e.g. cave, sea bottom, city (all lack producers), rain

water pond with bloom of toxic algae (lack consumers).

Various Components : An ecosystem consists of two types

of components - biotic and abiotic. Biotic components are living

beings, the abiotic components are non-living that includes inorganic

substances, organic substances and physical factors.

4 Environmental Science

Biotic Component : The living organisms present in an

ecosystem form the biotic components. They are classified into

three categories—producers, consumers and reducer or

decomposer.

Producers : They are autotrophic plants which synthesize

organic food from inorganic raw materials using the energy of sun

(exception - chemosynthetic bacteria). On land producers are

usually large rooted green plants while in deep water ecosystems

they are rootless algar floating or submerged in water. Autotrophs

are sometimes called primary producers.

Consumers : They are mainly animals. They are unable to

synthesize their food so depend upon other organisms or particulate

organic matter (food) produced by producers. They are known as

heterotrophs. They are of two main categories, herbivores and

carnivores. The herbivores called primary consumers depend upon

green plants for their food. Insects (aphides, bugs, ants), rodents

and ruminants are the common herbivores in terrestrial habitats

and small crustaceans and molluscs in aquatic habitats. Goat,

Cow, deer, rabit etc., are the common animals which are primary

consumers.

The herbivores are used as food by primary carnivores

(secondary consumers) (e.g., grasshopper, frog) which in turn are

used as food by secondary carnivores (tertiary consumers) (e.g.

snake that eats frog or birds which eat fish). In addition there may

be top carnivores which are not further preyed upon (e.g., Falcon,

Lion etc.)

Decomposers : (Osmotrophs = Saprotrophs = (Sapros = to

decompose) (also called micro-consumers). They include

fungi and bacteria which attack the dead bodies of producers

and consumers and break down the complex compounds of

dead protoplasm, absorb some of the decomposition products and

release inorganic nutrients to the environment for reuse by the

producers.

Thus there is a cyclic exchange of materials between living

community and the abiotic environment of an ecosystem.

Basic System 5

Abiotic Components

The non-living factors prevailing in an ecosystem form the

abiotic components. These are further divided into following three

parts:

(i) Climatic: includes light, temperature, wind, water etc.

(ii) Inorganic substances: nitrogen, calcium, sulphur,

phosphorus etc.

(iii) Organic compounds: protein, carbohydrates and lipids

which are linked between abiotic and biotic components.

The various steps through which food energy passes into an

ecosystem are called trophic levels. All green plants or producers

belong to first trophic or T1-level. All the herbivores or primary

consumers derive their energy from the producers belong to second

trophic or T2

-level, where as all the primary carnivores or secondary

consumers belong to third trophic level or T3

and the secondary

carnivores or tertiary consumers belong to fourth trophic level or

T4

. Quartenary consumers (Top carnivores) generally belong to

T5

trophic level. Decomposers form the last or detritus trophic

level (T6

).

Chain of Food

A food chain is a series of populations through which food

energy moves in an ecosystem. A food chain is simple if it has

only one trophic level besides the decomposers. A complex food

chain has both producers and consumer trophic level. The idea of

food chain was introduced by C. Elton. This idea describes the

linear series of species, generally involving plants (autotrophs),

herbivors and one or two successive sets of predators (a predator

chain) or alternatively, the series of parasites and hyperparasites

exploiting a host (a parasitic chain), saprophytic chains exploiting

dead tissues are now known to be very important.

Web of Food

It is a network of food chains which become interconnected

at various trophic levels so as to form at number of feeding

connections amongst different organisms of a biotic community. An

6 Environmental Science

organism can operate at more than one trophic level and obtains

its requirement of food from different sources. Similarly an organism

may be eaten by a number of different-organisms. Therefore, in

nature linear and independent food chains are very rare. Instead

several food chains are linked together. A food web opens several

alternate pathways for the flow of food energy. It also allows an

organism to obtain its food from two or more types of organisms

of the lower trophic level. Thus a field mouse may be eaten by a

wild cat, a snake or an owl. Similarly wild cats eat a number of

herbivores like squirrel, birds, mice etc. A wolf or jackal can eat

both rabbit and deer. The food web helps in maintaining the stability

of the ecosystem by keeping the different species under check and

maintain a state of equilibrium called homoeostasis.

Flow of Energy

Biological activity needs utilization of energy. Solar energy is

transformed from radiant to the chemical form in photosynthesis

and from chemical to mechanical and heat form in cellular activities.

Entrance of energy, its retention within the ecosystem and dissipation

into space are governed by laws of thermo dynamics.

(1) Energy can not be destroyed or created but is simply

converted from one form to the other.

(2) Processes involving energy transformation will not occur

spontaneously unless there is degradation of energy from

non random to a random form.

In an ecosystem all energy is provided by the sun of the

sunlight energy only 1% is stored by plants in photosynthesis. This

small amount of energy is sufficient to maintain all life on the

surface of the globe. All of the energy stored by the autotrophs

in the form of the food is available to the herbivores as food.

Herbivores are primary consumers but they can store only 10%

of this energy in their biomass and remaining 90% is used by them

in life activities. In the same way herbivores are eaten by carnivores

e.g. lion eats a deer. Thus only 10% of energy of lower trophic level

can be captured by the organisms of next higher trophic level. This

is known as Ten percent law.

Basic System 7

Pyramid of Ecology

An ecological pyramid is graphic representation of a parameter

like number, biomass or energy in a food chain at successive

trophic levels with producers at the base, top carnivores at the top

and other consumers forming intermediate tiers. The ecological

pyramids are of the following types.

Number Pyramid

In this type of pyramid the number of individual organisms at

each trophic level is shown. The pyramid may be upright or inverted.

In grassland and crop ecosystems the pyramid may be upright

where the producers are maximum in number and primary,

secondary and tertiary consumers constitute the successive tiers,

last tier makes the apex. In a tree ecosystem the pyramid is

inverted i.e., one single tree which is primary producer has got

large number of birds on it (Primary consumers) which have large

number of insects outside their body (Secondary consumers).

Biomass Pyramid

The total fresh or dry weight of all living organisms in a certain

unit area is called biomass. The amount of new biomass produced

in a single growing season is called yield. The pyramid of biomass

may be upright (terrestrial ecosystem) or inverted (aquatic

ecosystem). In terrestrial ecosystem (Forest) the biomass of primary

producers is maximum and biomass of top carnivores is minimum.

In aquatic ecosystem the biomass of consumers is more than that

of primary producers.

Energy Pyramid

The type of pyramid shows energy accumulation pattern at

different trophic levels. Such a pyramid of all ecosystem is upright.

Primary producers are characterised by maximum value and at

each successive tiers of consumers the energy value per square

meter per year is decreased by approximately 1/10. Thus there is

noted a gradual decrease in the energy content at successive

trophic level from producers to consumers.

8 Environmental Science

Significant Ecosystems

In nature ecological grouping of plants and animals extends

over large areas. Two major types of ecosystems are recognised

in nature. These are:

1. Aquatic ecosystem: Further divided into

(a) Fresh water ecosystem

(b) Marine ecosystem

2. Terrestrial ecosystem. The major terrestrial ecosystem of

the world are of four types

(a) deserts

(b) grasslands

(c) tundra

(d) forests

Pond of Fresh Water

It has a structure having the abiotic and biotic components.

Location, size, depth and substrates of a pond influence the biology

of pond ecosystem. A pond ecosystem is a self-sufficient, self￾regulating system.

Abiotic Components

Temperature, light, pH of water and several basic inorganic

and organic substances like H2

O, Co2

,O2

, N2

, PO4

, Ca, S and

carbohydrates, proteins, lipids etc., make the abiotic components.

Biotic Components

Producers: This category includes green plants which may be

submerged, free-floating or amphibious e.g., Hydrilla,

Ceratophyllum, Utricularia, Vallisnaria, Jussiaea, Wolffia, Lemna,

Eichornia, Azoll, Salvinia, Trapa: They are minute floating and

suspended algal phytoplanktons like Ulothrix, Spirogyra,

Oedogonium, Chlamydomonas, Volvox, Pandorina, Eudorina,

Anabaena.

Consumers: These include

(i) Primary Consumers: Herbivores

Basic System 9

(a) Zooplanktons: Some protozoans : Dileptus, Coleps,

Euglena etc. rotifiers, Lecane, Asplanchana etc.,

Crustaceans, Cyclops, Stenocrypis etc., feeding upon

phytoplanktons.

(b) Benthos : Larvae of insects, beetles, fishes, mites,

molluscs, crustaceans. Their biomass is determined.

(ii) Secondary consumers : Insects, water beetles, frogs, fishes

etc. feeding upon primary consumers are included under

this group.

(iii) Tertiary Consumers : Big fishes eating small fishes belong

to this group.

(c) Decomposers : Several bacteria, fungi and actino￾mycetes represent this group e.g., Aspergillus,

Saprolegnia, Fusarium, Rhizopus.

Terrestrial Ecosystem : Forest Ecosystem is considered as

an example here. Forests are natural plant communities with

dominance of phanerogams. In India forests occupy approx. 1/10

of the land area. Forests can be divided into the 4 broad categories.

1. Tropical (wet evergreen, semi evergreen, moist deciduous

and dry deciduous)

2. Sub-tropical

3. Temperate

4. Alpine

Abiotic Components

This includes inorganic and organic substances present in the

atmosphere and soil. The climate (temperature, light, rain fall etc.)

and soil (minerals) vary from forest to forest. In addition to minerals

the occurrence of litter is the characteristic feature of majority of

forests. Through litter decomposition approx. 90% energy trapped

in the ecosystem by autotrophs dissipates into space as heat

energy. The litter fall increases with decreasing latitudes.

Biotic Components

(A) Producers: They are mainly represented by trees but shrubs

10 Environmental Science

and ground flora are also found. Depending upon the kinds

of the forests the flora varies.

(B) Consumers:

(i) Primary Consumers are small animals feeding on tree

leaves include ants, beetles, flies, bugs, spiders, leaf

hoppers etc. neelgai, deer, elephants, moles, squirrels

and fruit bats are large animals which feed upon shoots

and/or fruits.

(ii) Secondary consumers are different kind of birds

snakes, lizards, feeding on primary consumers.

(iii) Tertiary Consumers are tigers and lions are top

carnivores.

(C) Decomposers : Streptomyces (Bacteria) and Fungi (Asper￾gillus. Alternaria, Fusarium) are helpful in decomposing

the litter.

Evolution and Development 11

2

Evolution and Development

In our country Science is witnessed to be taught from very

early days. If we look at the development of science in India, we

find that very early in her civilisation India developed a great

interest in mathematics and Ayurveda. During British Empire

introduction of modern science in India was extremely slow, and

the development of science in India was greatly accelerated after

independence.

Culture and Tradition

Before the rise of modern science in Europe, around the 17th

century, the level of advancement in sciences (astronomy,

mathematics, medicine, biology, metaphysics, etc) achieved by

ancient and medieval societies in the old world did not differ

appreciably from one cultural area to another. In India the

development of sciences is as old as her civilisation itself. Her

peculiar geographical position enabled her to become the natural

meeting ground of many nations and cultures and, in consequence,

played an important role in the transmission and diffusion of ideas

very early in her civilisation, India developed medical and alchemical

practices of the Ayurveda. In mathematics, India developed a great

interest and aptitude and made notable contributions to the number

theory, the decimal place value, algorism, trigonometry and algebra.

12 Environmental Science

Origin and Growth

In the beginning of the nineteenth century people with varying

degrees of scientific background (medical men, naturalists and

engineers) started coming to India from Europe, at first in search

of services under local princes and chieftains and later on to man

the scientific surveys and establishments set up by the government.

These men framed in European institutions and laboratories, spent

the best part of their lives in India and left an excellent record of

their work in various branches of science.

Despite such long contacts, introduction of modern science in

India was extremely slow. There were many causes of this delayed

reaction. The European scientific world in India was limited to field

sciences and not to basic sciences that depended on mathematics

and laboratory work. Indian fauna and flora attracted the attention

of European naturalists from the seventeenth century. Modern

zoological researchers in India had their beginnings in random and

scattered observations by the naturalists on elephants, fishes,

serpents, molluscs, birds and mammals.

The Colonial Government adopted from the beginning a policy

of secrecy and exclusion of Indians from Government scientific

work. For technological jobs not considered of military importance,

restrictions against the employment of Indians were relaxed as

they could be employed very cheaply. As an example of the low

salaries to trained and qualified Indians/ the order of the Governor￾General dated 28th January 1835, establishing the Calcutta Medical

College, regulated that “as inducement for pupils of a respectable

class to enter the Institution, the pay of the Native Doctors, who

shall have been educated at the College, and have received the

certificates of qualifications, shall be Rs. 30.00 p.m. rising to

Rs. 50.00 p.m. after 14 years of service, whereas an European

Assistant to the Superintendent of the college shall draw a staff

salary of Rs. 600.00 p.m. in addition to his registered pay and

allowances.” Calcutta Medical College established in 1835 under

a number of capable teachers, became an important institution,

for the study of anatomy, physiology and medicine (along with

surgery), as well as of chemistry, botany and natural philosophy.