Filetype PDF | Posted on 22 Jan 2023 | 3 years ago
Authentication
digital resources
190x Filetype PDF File size 1.22 MB Source: www.ugc.ac.in
UNIT 3:
Ecosystems
3.13.1 CONCEPT OF AN ECOSYSTEMCONCEPT OF AN ECOSYSTEM 5454
3.1 CONCEPT OF AN ECOSYSTEM 54
3.13.1 CONCEPT OF AN ECOSYSTEMCONCEPT OF AN ECOSYSTEM 5454
3.1.1 Understanding ecosystems 55
3.1.2 Ecosystem degradation 55
3.1.3 Resource utilisation 56
3.2 3.2 STRUCTURE AND FUNCTIONS OF AN ECOSYSTEMSTRUCTURE AND FUNCTIONS OF AN ECOSYSTEM 5656
3.2 STRUCTURE AND FUNCTIONS OF AN ECOSYSTEM 56
3.2 3.2 STRUCTURE AND FUNCTIONS OF AN ECOSYSTEMSTRUCTURE AND FUNCTIONS OF AN ECOSYSTEM 5656
3.3 3.3 PRODUCERS, CONSUMERS AND DECOMPOSERSPRODUCERS, CONSUMERS AND DECOMPOSERS 5757
3.3 PRODUCERS, CONSUMERS AND DECOMPOSERS 57
3.3 3.3 PRODUCERS, CONSUMERS AND DECOMPOSERSPRODUCERS, CONSUMERS AND DECOMPOSERS 5757
3.4 3.4 ENERGY FLOW IN THE ECOSYSTEMENERGY FLOW IN THE ECOSYSTEM 5858
3.4 ENERGY FLOW IN THE ECOSYSTEM 58
3.4 3.4 ENERGY FLOW IN THE ECOSYSTEMENERGY FLOW IN THE ECOSYSTEM 5858
3.4.1 The water cycle 58
3.4.2 The Carbon cycle 59
3.4.3 The Oxygen cycle 60
3.4.4 The Nitrogen cycle 60
3.4.5 The energy cycle 61
3.4.6 Integration of cycles in nature 62
3.53.5 ECOLOGICAL SUCCESSIONECOLOGICAL SUCCESSION 6262
3.5 ECOLOGICAL SUCCESSION 62
3.53.5 ECOLOGICAL SUCCESSIONECOLOGICAL SUCCESSION 6262
3.63.6 FOOD CHAINS, FOOD WEBS AND ECOLOGICAL PYRAMIDSFOOD CHAINS, FOOD WEBS AND ECOLOGICAL PYRAMIDS 6262
3.6 FOOD CHAINS, FOOD WEBS AND ECOLOGICAL PYRAMIDS 62
3.63.6 FOOD CHAINS, FOOD WEBS AND ECOLOGICAL PYRAMIDSFOOD CHAINS, FOOD WEBS AND ECOLOGICAL PYRAMIDS 6262
3.6.1 The food chains 62
3.6.2 The food webs 63
3.6.3 The ecological pyramids 63
3.73.7 INTRODUCTION, TYPES, CHARACTERISTIC FEATURES, STRUCTURE AND FUNCTIONSINTRODUCTION, TYPES, CHARACTERISTIC FEATURES, STRUCTURE AND FUNCTIONS 6363
3.7 INTRODUCTION, TYPES, CHARACTERISTIC FEATURES, STRUCTURE AND FUNCTIONS 63
3.73.7 INTRODUCTION, TYPES, CHARACTERISTIC FEATURES, STRUCTURE AND FUNCTIONSINTRODUCTION, TYPES, CHARACTERISTIC FEATURES, STRUCTURE AND FUNCTIONS 6363
3.7.1 Forest ecosystem 65
3.7.2 Grassland ecosystem 70
3.7.3 Desert ecosystem 74
3.7.4 Aquatic ecosystems (ponds, lakes, streams, rivers, estuaries, oceans) 75
Ecosystems
53
Chapter3.p65 53 4/9/2004, 5:08 PM
3.1 CONCEPT OF AN ECOSYSTEM3.1 CONCEPT OF AN ECOSYSTEM the Western and Eastern Ghats, the semi-arid
3.1 CONCEPT OF AN ECOSYSTEM
3.1 CONCEPT OF AN ECOSYSTEM3.1 CONCEPT OF AN ECOSYSTEM
desert in the West, the Deccan Plateau, the
An Ecosystem is a region with a specific and Coastal Belts, and the Andaman and Nicobar
recognizable landscape form such as forest, Islands. These geographically distinctive areas
grassland, desert, wetland or coastal area. The have plants and animals that have been adapted
nature of the ecosystem is based on its geo- to live in each of these regions.
graphical features such as hills, mountains,
plains, rivers, lakes, coastal areas or islands. It is At an even more local level, each area has sev-
eco-eco-
also controlled by climatic conditions such as the eral structurally and functionally identifiable eco-
eco-eco-
systemssystems
amount of sunlight, the temperature and the systems such as different types of forests, grass-
systemssystems
rainfall in the region. The geographical, climatic lands, river catchments, mangrove swamps in
and soil characteristics form its non-living (abi- deltas, seashores, islands, etc. to give only a few
otic) component. These features create condi- examples. Here too each of these forms a habi-
tions that support a community of plants and tat for specific plants and animals.
animals that evolution has produced to live in
these specific conditions. The living part of the Ecosystems have been formed on land and in
ecosystem is referred to as its biotic component. the sea by evolution that has created species to
live together in a specific region. Thus ecosys-
Ecosystems are divided into terrestrial or land- tems have both non-living and living compo-
based ecosystems, and aquatic ecosystems in nents that are typical to an area giving it its own
water. These form the two major habitat condi- special characteristics that are easily observed.
tions for the Earths living organisms.
Definition:Definition:
Definition: The living community of plants and
Definition:Definition:
All the living organisms in an area live in com- animals in any area together with the non-liv-
munities of plants and animals. They interact ing components of the environment such as soil,
with their non-living environment, and with each air and water, constitute the ecosystem.
other at different points in time for a large num-
ber of reasons. Life can exist only in a small pro- Some ecosystems are fairly robust and are less
portion of the earths land, water and its atmo- affected by a certain level of human disturbance.
sphere. At a Others are highly fragile and are quickly de-
global level the thin skin of the earth
on the land, the sea and the air, forms the bio- stroyed by human activities. Mountain ecosys-
sphere. tems are extremely fragile as degradation of
forest cover leads to severe erosion of soil and
bio-bio- changes in river courses. Island ecosystems are
At a sub-global level, this is divided into bio-
bio-bio-
geographical realms, geographical realms, easily affected by any form of human activity
geographical realms, eg. Eurasia called the
geographical realms, geographical realms,
palaeartic realm; South and South-East Asia (of which can lead to the rapid extinction of sev-
which India forms a major part) is the Oriental eral of their unique species of plants and ani-
realm; North America is the Nearctic realm; mals. Evergreen forests and coral reefs are also
South America forms the Neotropical realm; examples of species rich fragile ecosystems
Africa the Ethiopian realm; and Australia the which must be protected against a variety of
Australian realm. human activities that lead to their degradation.
River and wetland ecosystems can be seriously
biogeo-biogeo- affected by pollution and changes in surround-
At a national or state level, this forms biogeo-
biogeo-biogeo-
graphic regions. graphic regions. ing landuse.
graphic regions. There are several distinctive
graphic regions. graphic regions.
geographical regions in India- the Himalayas, the
Gangetic Plains, the Highlands of Central India,
Environmental Studies for Undergraduate Courses
54
Chapter3.p65 54 4/9/2004, 5:08 PM
3.1.1 Understanding ecosystems3.1.1 Understanding ecosystems • How does the ecosystem work?
3.1.1 Understanding ecosystems
3.1.1 Understanding ecosystems3.1.1 Understanding ecosystems
The ecosystem functions through several
Natural ecosystems include the forests, grass- biogeochemical cycles and energy transfer
lands, deserts, and aquatic ecosystems such as mechanisms. Observe and document the
ponds, rivers, lakes, and the sea. Man modified components of the ecosystem which con-
ecosystems include agricultural land and urban sists of its non-living or abiotic features such
or industrial land use patterns. as air, water, climate and soil. Its biotic com-
ponents, the various plants and animals.
Each ecosystem has a set of common features Both these aspects of the ecosystem inter-
that can be observed in the field: act with each other through several func-
tional aspects to form Natures ecosystems.
• What does the ecosystem look like? Plants, herbivores and carnivores can be
One should be able to describe specific fea- seen to form food chains. All these chains
tures of the different ecosystems in ones are joined together to form a web of life
own surroundings. Field observations must on which man depends. Each of these use
be made in both urban and natural sur- energy that comes from the sun and pow-
roundings. ers the ecosystem.
• What is its structure?
3.1.2 Ecosystem degradation3.1.2 Ecosystem degradation
Is it a forest, a grassland, a water body, an 3.1.2 Ecosystem degradation
3.1.2 Ecosystem degradation3.1.2 Ecosystem degradation
agricultural area, a grazing area, an urban
area, an industrial area, etc.? Ecosystems are the basis of life itself! The natu-
ral ecosystems in the wilderness provide a vari-
What you should see are its different char- ety of products and are regions in which a num-
acteristics. A forest has layers from the ber of vital ecological processes are present,
ground to the canopy. A pond has differ- without which human civilization would not be
ent types of vegetation from the periphery able to exist.
to its center. The vegetation on a mountain
changes from its base to its summit. Ecosystems are however frequently disrupted by
human actions which lead to the extinction of
• What is the composition of its plant and species of plants and animals that can live only
animal species? in the different natural ecosystems. Some spe-
List the well-known plants and animals you cies if eliminated seriously affect the ecosystem.
can see. Document their abundance and These are called keystone species. Extinction
numbers in nature: very common, common, occurs due to changes in land use. Forests are
uncommon, rare. Wild mammals will not deforested for timber, wetlands are drained to
be seen in large numbers, cattle would be create more agricultural land and semi arid
common. Some birds are common – which grasslands that are used as pastures are changed
are the most common species? Insect spe- into irrigated fields. Pollution from industry and
cies are very common and most abundant. waste from urban settings can also lead to ex-
In fact there are so many that they cannot tinction of several species.
be easily counted.
The reason for the depletion of natural resources
is twofold – our rapidly exploding population
that needs to sustain itself on resources, and
the growth of affluent societies, which consume
Ecosystems
55
Chapter3.p65 55 4/9/2004, 5:08 PM
and waste a very large proportion of resources The key to this issue is the need for an equi-
and energy. Increasing extraction of resources table distribution of all types of natural re-
is at the cost of natural ecosystems, leading to a sources. A more even sharing of resources within
derangement of their important functions. Each the community can reduce these pressures on
of us in our daily lives use a variety of resources. the natural ecosystems.
If tracked back to their source, one finds that
the resources were originally obtained from
3.2 STRUCTURE AND FUNCTIONS OF AN3.2 STRUCTURE AND FUNCTIONS OF AN
nature and natural ecosystems. Our insensitiv- 3.2 STRUCTURE AND FUNCTIONS OF AN
3.2 STRUCTURE AND FUNCTIONS OF AN3.2 STRUCTURE AND FUNCTIONS OF AN
ECOSYSTEMECOSYSTEM
ity to using resources carefully has produced ECOSYSTEM
ECOSYSTEMECOSYSTEM
societies that nature can no longer sustain. If
Structural aspectsStructural aspects
one thinks before wasting resources such as wa- Structural aspects
Structural aspectsStructural aspects
ter, reusing and recycling paper, using less plas-
tics that are non-degradable, culminatively this Components that make up the structural as-
can have positive implications on the integrity pects of an ecosystem include:
of our natural resource base and conserve the
resources that nature provides. 1) Inorganic aspects – C, N, CO , H O.
2 2
Ecosystems and man: Every region of our earth 2) Organic compounds – Protein, Carbo-
has different ecosystems based on its climatic hydrates, Lipids – link abiotic to biotic
conditions and geographical feature. There are aspects.
terrestrial ecosystems on land and aquatic eco-
systems in water. 3) Climatic regimes – Temperature, Mois-
ture, Light & Topography.
3.1.3 Resource utilisation3.1.3 Resource utilisation
3.1.3 Resource utilisation 4) Producers – Plants.
3.1.3 Resource utilisation3.1.3 Resource utilisation
Most traditional societies used their environment 5) Macro consumers – Phagotrophs – Large
sustainably. Though inequality in resource utili- animals.
zation has existed in every society, the number
of individuals that used a large proportion of 6) Micro consumers – Saprotrophs, absorb-
resources was extremely limited. In recent times ers – fungi.
the proportion of rich people in affluent soci-
eties, grew rapidly. Inequality thus became a se-
rious problem. Whereas in the past many re- Functional aspectsFunctional aspects
Functional aspects
Functional aspectsFunctional aspects
sources such as timber and fuel wood from the
forest were extracted sustainably, this pattern 1) Energy cycles.
has drastically changed during the last century.
The economically better off sections began to 2) Food chains.
use greater amounts of forest products, while
those people who lived in the forest became 3) Diversity-interlinkages between organ-
increasingly poor. Similarly the building of large isms.
irrigation projects led to wealth in those areas
that had canals, while those who hand to re- 4) Nutrient cycles-biogeochemical cycles.
main dependent on a constant supply of water
from the river itself, found it difficult to survive. 5) Evolution.
Environmental Studies for Undergraduate Courses
56
Chapter3.p65 56 4/9/2004, 5:08 PM
no reviews yet
Please Login to review.
