Ecology and Environment: Introduction, Definition


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● Ecology is a science, in which study of

organism is undertaken in relation to

their environment. This science

developed in response to the increasing

awareness of inter- relationships

between plants, animals and their

physical habitats.

● The term ecosystem was first used by

AG Tansley in 1935, who defined

ecosystem as a particular category of

physical system, consisting of organisms

and inorganic components in a relatively

stable equilibrium which is open and of

various sizes and kinds.

Components of Ecosystem

● Abiotic Components are the non-living

components, e.g. air, water, soil,

suspended particulate matter etc.

● Biotic Components includes plants,

animals and micro-organism.

● The living organism in an ecosystem

can be divided into three categories


● Producers are organisms that can make

organic energy resources from abiotic

components of the environment. They

produce their food themselves.


● Consumers are those organisms that

gather energy by consuming organic

material from other organisms. Primary

consumers are those organisms, who

consume mainly producers. Primary

consumers are also known as Herbivores.

● Secondary consumers are those

organisms, who consume mainly

primary consumers. Tertiary consumers

are organisms that consume secondary

consumers. Tertiary consumers are

carnivores. Omnivores feed on both

producers and other consumers.

● Detritovores consume detritus

(dead material of plants and animals).


● Decomposers are organisms that break

down dead or decaying organisms.

Decomposers are heterotrophic which

means that they use organic substrates to

get their energy and carbon and

nutrients for their growth and

development e.g. bacteria and fungi.

Functions of Ecosystem

The main functions of an ecosystem are as


(i) Materials or nutrient cycle

(ii) Biological or ecological regulation

● Foodchain The flow of energy from of

one organism to another in a sequence of

food transfer is known as a foodchain. A

simple foodchain is like the following

Grass→ Insect→ Frogs→ Snake→ Hawk

● Food Web A network of foodchains or

feeding relationships, by which energy and

nutrients are passed on from one specie of

living organism to another is called food


● Trophic Levels Trophic levels are the

feeding position in a foodchain such as

primary producers, herbivore, primary

carnivore etc. Generally, green plants

form the first trophic level, the

producers, herbivores form the second

trophic level, while carnivores and

omnivores form the third and even the

fourth trophic levels.

● Ecological Pyramid An ecological

pyramid is a graphical representation

designed to show the number of

organisms, energy relationships and

biomass of an ecosystem. They are also

called Eltonian Pyramids after Charles

Elton, who developed the concept of

ecological pyramids. Producer organisms

(usually green plants) from the base of

the pyramid, with succeeding levels

above representing the different tropic


● Succeeding levels in the pyramid

represent the dependence of the

organisms at a given level on the

organisms at lower level.

● Pyramid of Biomass Biomass is

renewable organic (living) material. A

pyramid of biomass is a representation of

the amount of energy contained in

biomass at different trophic levels for a

particular time.

● It is measured in grams per meter or

calories per meter. This demonstrates the

amount of matter lost between trophic


● Pyramid of Energy The pyramid of

energy represents the total amount of

energy consumed at each trophic level.


Environmental pollution is the effect of

undesirable changes in our surroundings

that have harmful effects on plants, animals

and human beings.

Pollutants Pollutants are substances which

cause pollution. They could be in any from

solid, liquid or gaseous.

● A primary pollutant is substance emitted

directly from a source.

● A secondary pollution is not directly

emitted as such, but forms, when other

pollutants (primary pollutants) react in

the atmosphere.

Primary pollutants

● Sulphur dioxide (SO )2

, nitrogen oxides

(NO )2

, carbon monoxide (CO), chloro-

fluoro carbons (CFCs), carbon dioxide

(CO )2

, Suspended Particulate Matter

(SPM) and Ammonia (NH )3


organic compounds, toxic metals etc.

Secondary pollutants

1. Particulate matter formed from

gaseous primary pollutants and

compounds in photochemical smog,

such as nitrogen dioxide.

2. Ground level ozone (O )3

formed from


and Volatile Organic Compounds


3. Peroxyacety l Nitrate (PAN) similarly

formed from NO2

and VOCs.

Air Pollution

It is the contamination of air by a variety of

substances causing health problems and

damaging our environment.

Air Pollutants

Some of the most common air pollutants are

as follows.

● Carbon Monoxide (CO) is produced from

incomplete combustion of fuel such as

natural gas, coal and wood.

● It is also produced in tobacco smoke. It

slows our reflexes and makes us feel


● Carbon Dioxide ( ) CO2

is the principal

greenhouse gas and is primarily

responsible for the greenhouse effect. It

can be formed from all types of common

human activities, such as burning fuels

and even breathing.

● Chlorofluorocarbons (CFCs) were

generally used in great quantities in

industry, for refrigeration and

air-conditioning and in consumer


● Ozone ( )O3

gas occurs naturally in the

upper atmosphere where it shields the

Earth from the Sun’s dangerous

ultraviolet rays. When found at ground

level, it’s a pollutant.

● Nitrogen Oxide and Sulphur Dioxide

are major contributors to smog and acid

rain. These gases both react with

volatile organic compounds to form

smog, which can cause respiratory

problems in humans. Acid rain can

harm vegetation, change the chemistry

of river and lake water by lowering the

pH which is harmful to animal life and

react with the marble statues and

buildings to decompose them.

Controls/Measures of Air


● Suitable fuel selection

● Modification in industrial processes

● Correct selection of manufacturing sites

● More efficient engines

● Awareness for using public transport so

that air pollution is minimised

Water Pollution

● It is the contamination of water bodies

(e.g. lakes, rivers, oceans, aquifers and

groundwater). Water pollution occurs

when pollutants are discharged directly

or indirectly into water bodies without

adequate treatment to remove harmful


● Biological Oxygen Demond (BOD) It

is a measurement of amount of

dissolved oxygen that is used by aerobic

micro-organisms when decomposing

organic matter in water. It is an

important water quality parameter and

is an indicator of organic pollution.

Control/Measures of Water


● Mass social awareness should be


● Ground water pollution can be

eliminated by maintaining strict

restrictions regarding waste disposal.

● Industrial effluents should be effectively

recycled, before releasing in water.

● Biodiversity is often seen in the terms of

three fundamental and hierarchically

related levels of biological organisation.

● Genetic diversity represents the

heritable variation within and between

population of organisms.

● Species diversity refers to number of

species in a site or habitat.

● Ecosystem diversity refers to diversity

of different organisms at the ecosystem,

habitat or community level.

Biodiversity Hotspots

● A biodiversity hotspot is a bio-geographic

region with a significant reservoir of

biodiversity that is under threat from

humans. The concept of biodiversity

hotspots was given by Norman Myers.

● To qualify as a biodiversity hotspot a

region must meet two strict criterias. It

must contain at least 0.5% or 1500

species of vascular plants as endemics

and it has to have lost at least 70% of its

primary vegetation. India has two

biodiversity hotspots—Western Ghats

and Eastern Himalayas. Indo-Burma

Region and Sundaland (including

Nicobar group of Islands).

Biodiversity Conservation

Conservation is planned management of

natural resources to retain the balance in

nature and retain the diversity. It

emphasises on the wise use of natural

resources by accepting the idea of

sustainable development. Conservation of

biodiversity is carried out in the following


Method of Conservation

The method of conservation of biodiversity

can be classified into two groups.

In-Situ (On Site)

Conservation include protection of plants

and animals within their natural habitats

or in protected areas. Protected areas are

land or sea dedicated to protect and

maintain biodiversity. Examples are

Biosphere Reserves, National Parks,

Wildlife Sanctuaries, etc.

Ex-Situ (Off Site)

Conservation of plants and animals outside

their natural habitats. These include

botanical gardens, zoos, gene banks of seed,

tissue culture and cryopreservation.

Threatened Species

Threatened species are any species

(including animals, plants, fungi, etc.)

which are vulnerable to endangering in the

near future. Species that are threatened

are sometimes characterised by the

population dynamics measure of critical

depensation, a mathematical measure of

biomass related to population growth rate.

This quantitative metric is one method of

evaluating the degree of danger.


The International Union for Conservation

of Nature (IUCN) is the foremost authority

on threatened species, and treats

threatened species not as a single category,

but as a group of three categories,

depending on the degree to which they are

threatened :

● Vulnerable species : A vulnerable species

is one which has been categorised by the

International Union for Conservation of

Nature as likely to become endangered

unless the circumstances threating its

survival and reproduction improve.

● Endangered species : An endangered

species is a species which has been

categorised as indanger and is likely to

become extinct.

● Critically endangered species :

A critically endangered (CR) species is

one which has been categorised by the

International Union for Conservation of

Nature (IUCN) as facing a very high risk

of extinction in the wild. It is the highest

risk category assigned by the IUCN Red

List for wild species.

IUCN Red List

The IUCN Red List of Threatened Species

(also known as the IUCN Red List or Red

Data List), founded in 1964, is the world’s

most comprehensive inventory of the global

conservation status of biological species.

Climate Change

Climate change refers to long-term change

in the earth’s climate, especially a change

due to an increase in average atmospheric

temperature. In the past, Earth’s climate has

gone through warmer and cooler periods,

each lasting thousands of years.

Greenhouse Effect and Global


● The greenhouse gases (sometimes

abbreviated as GHG) in the atmosphere

absorbs and emits radiation within the

thermal infrared range. The process is the

fundamental cause of the greenhouse

effect. The primary greenhouse gases in

the Earth’s atmosphere are water vapour,

carbon dioxide, methane, nitrous oxide

and ozone. In the Solar System, the

atmosphere of Venus, Mars and Titan also

contain gases that cause greenhouse effects.

● Global Warming is the increase of Earth’s

average surface temperatue due to effect

of greenhouse gases, such as carbon

dioxide emissions from burning fossil fuels

or from deforestation.

Kyoto Protocol

● The Kyoto Protocol is a protocol to the

United Nations Framework Convention

on Climate Change (UNFCCC), aimed at

fighting global warming. The UNFCCC

is an international environmental

treaty with the goal of achieving the

‘‘stabilisation of greehouse gas

concentration in the atmosphere at a

level that would prevent dangerous

anthropogenic interference with the

climate system’’. The protocol was

initially adopted on 11th December,

1997 in Kyoto, Japan and entered into

force on 16th February, 2005. Second

commitment period of this protocol

started in 2013 and will end in 2020.

● The Intergovernmental Panel on

Climate Change (IPCC) has predicted

an average global rise in temperature of

1.4°C to 5.8°C between 1990 and 2100.

If successfully and completely imple-

mented, the Kyoto Protocol will reduce

that increase by somewhere between

0.02°C and 0.28°C by the year 2050.

Mission Included in Prime

Minister’s National Action Plan

for Climate Change (NAPCC)

● National solar mission

● National mission for enhanced energy


● National mission on sustainable habitat

● National water mission

● National mission for sustaining the

Himalayan ecosystem

● National mission for Green India

● National mission for sustainable


● National mission on strategic

knowledge for climate change


● Reducing Emissions from

Deforestation and Forest

Degradation (REDD) is an effort to

create a financial value for the

carbon stored in forests, offering

incentives to developing countries to

reduce emissions from forested lands

and invest in low carbon paths to

sustainable development.

● ‘REDD+’ goes beyond deforestation

and forest degradation and includes

the role of conservation, sustainable

management of forests and

enhancement of forest carbon


● The proper implementation of

REDD+ will contribute to protection

of biodiversity, resilience of forest

ecosystems and poverty reduction.

Ozone Layer Depletion

● The ozone layer is located within the

Stratosphere, about 24 km above the Earth’s


● The layer consist of ozone gas molecules that

are formed as the sunlight reacts with oxygen.

● The ozone layer is very important as it

protects life on Earth by filtering the Sun’s

dangerous ultraviolet radiation.

● Due to increased pollution on Earth,

chemicals such as Chloro Fluro Carbons

(CFCs) are destroying this protective ozone

layer, which could lead to increased health

risks and damage agricultural and acquatic


Montreal Protocol on Substances

that Deplete the Ozone Layer

● It is an international treaty designed to

protect the ozone layer from Chloro Fluoro

Carbons (CFCs).

● The treaty was opened for signature on 16th

September, 1987 and entered into force on

1st January, 1989, followed by a first meeting in May 1989

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