Module – III

Environment and Eco System

CONTENT
Environment:
 Introduction,
 Multidisciplinary nature of environmental studies-
Definition, scope and importance,
 Need for public awareness.
Ecosystem:
 Concept,
 Energy flow, Structure and function of an ecosystem.
 Food chains,
 Food webs and ecological pyramids,
 Forest ecosystem,
 Grassland ecosystem,
 Desert ecosystem and Aquatic ecosystems,
 Ecological succession.
ENVIRONMENT
 The word environment is derived from the French word
environner' meaning surroundings. Hence, everything
surrounding us is called "ENVIRONMENT".
 Environment literally means Surrounding in which we are
living.
 Environment includes all those things on which we are
directly or indirectly dependent for our survival, whether it
is living component like animals, plants or non living
component like soil, air water.
 Environmental Protection Act (1986) defined “Environment
as the sum total of water, air and land, their
interrelationship among themselves and with the human
beings, other living beings and property.”
 ENVIRONMENTAL STUDIES
 Environmental studies is a multidisciplinary academic
field which systematically studies human interaction with
the environment in the interests of solving complex
problems.
 Environmental studies brings together the principles of
the physical sciences, commerce/economics and social
sciences so as to solve contemporary environmental
problems.
SCOPE
The scope of environmental studies include:
1. Developing an awareness and sensitivity to the total
environment and its related problems
2. Motivating people for active participation in
environmental protection and improvement
3. Developing skills for active identification and
development of solutions to environmental problems
4. Imbibe and inculcate the necessity for conservation of
natural resources
5. Evaluation of environmental programs in terms of
social, economic, ecological and aesthetic factors.
IMPORTANCE OF ENVIRONMENTAL STUDIES:
Seven objectives have been identified:
 Daily Activities: It guides us to know how our developmental and day-
to-day activities affect environment and how we are affected by changes
in the environmental conditions.
 Decrease pollution: It guides us to create a pollution-free environment
(that is, clean air, water, land, and food) by adopting different methods of
preventing and controlling pollution.
 Utilization of Natural resource: It guides us to utilize our natural
resources such as water, forest, minerals, and fossil fuels in an efficient
manner, that is, with maximum utility and minimum wastage, by
adopting conservation and recycling strategies.
 Public awareness: It guides common public to live an eco-friendly
lifestyle by adopting the above three features, that is, knowing
environmental implications of one’s activities, preventing and controlling
pollution, and utilizing the resources efficiently in day-to-day activities.
 Industry: It guides industries to operate in an eco-friendly mode by
adopting clean and efficient technologies and installing pollution control
systems.
 Global Environmental Problem: It guides us to solve complex global
environmental problems such as climate change, ozone-layer depletion,
desertification, and energy crisis by using different interdisciplinary tools
and approaches.
NEED FOR PUBLIC AWARENESS:
 PREVENT THE ENVIRONMENT FROM FURTHER DEGRADATION: Increasing
population, Urbanization and poverty have generated pressure on the natural resources and
lead to a degradation of the environment. TO PREVENT THE ENVIRONMENT FROM
FURTHER DEGRADATION, the supreme court has ordered and initiated environmental
protection awareness through government and non-government agencies to take part in
protecting our environment.
 Public participation: Environmental pollution cannot prevented by laws alone. Public
participation is equally important with regard to environmental protection.
 Awareness: Environmental Education (EE) is a process of learning by giving an overall
perspective of knowledge and awareness of the environment.
 Skill Development: It sensitizes the society about environmental issues and challenges
interested individuals to develop skills and expertise thereby providing appropriate
solutions.
 Climate change, loss of biodiversity, declining fisheries, ozone layer depletion, illegal trade of
endangered species, destruction of habitats, land degradation, depleting ground water
supplies, introduction of alien species, environmental pollution, solid waste disposal, storm
water and sewage disposal pose a serious threat to ecosystems in forest, rural, urban and
marine ecosystems.
 Both formal and informal education on the environment will give the interested individual
the knowledge, values, skills and tools needed to face the environmental challenges on a local
and global level.
 As the earth’s natural resources are dwindling and our environment is being increasingly
degraded by human activities, it is evident that something needs to be done.
 Individually we can play a major role in environment management. We can reduce wasting
natural resources and we can act as watchdogs that inform the Government about sources
that lead to pollution and degradation of our environment. This can only be made possible
through mass public awareness. Mass media such as newspapers, radio, television, strongly
influence public opinion. However, someone has to bring this about.
ECO SYSTEM
An ‘Ecosystem’ is a region with a specific and recognizable landscape form
such as forest, grassland, desert, wetland or coastal area.
Ecosystems are divided into terrestrial or land based ecosystems, and
aquatic ecosystems in water. These form the two major habitat conditions
for the Earth’s living organisms.

Ecosystems have been formed on land and in the sea by evolution that has
created species to live together in a specific region. Thus ecosystems have both
non-living and living components that are typical to an area giving it its own
special characteristics that are easily observed.
 COMPONENTS OF ECOSYSTEM
Each ecosystem has two main components:
(1) Abiotic
(2) Biotic
(1) Abiotic Components:
 The abiotic components of an ecosystem are all of the
nonliving elements. They include the water, the air, the
temperature and the rocks and minerals that make up the
soil.
 Abiotic components of an ecosystem might include how much
rain falls on it, whether it is fresh water or salt water, how
much sun it gets or how often it freezes and thaws.
Abiotic components are mainly of two types:
(a) Climatic Factors:
Which include rain, temperature, light, wind, humidity etc.
(b) Edaphic Factors:
 Which include soil, pH, topography minerals etc.
(2) Biotic Components:
 The living organisms including plants, animals and micro-
organisms (Bacteria and Fungi) that are present in an
ecosystem form the biotic components. The biotic components
of the ecosystem both live on and interact with the abiotic
components.
On the basis of their role in the ecosystem the biotic
components can be classified into three main groups:
(A) Producers
(B) Consumers
(C) Decomposers or Reducers.
(A) Producers:
 Producers are the living organisms in the ecosystem that take
in energy from sunlight and use it to transform carbon dioxide
and oxygen into sugars.
 Plants, algae and photosynthetic bacteria are all examples of
producers. As the green plants manufacture their own food
they are known as Autotrophs (i.e. auto = self, trophos =
feeder).
 Producers form the base of the food web and are generally the
largest group in the ecosystem by weight, or biomass.
 They also act as an interface with the abiotic components of
the ecosystem during nutrient cycles as they incorporate
inorganic carbon and nitrogen from the atmosphere.
 The chemical energy stored by the producers is utilized partly
by the producers for their own growth and survival and the
remaining is stored in the plant parts for their future use.
(B) Consumers:
 Consumers are living organisms in the ecosystem that get
their energy from consuming other organisms.
Conceptually, consumers are further subdivided by what
they eat.
 Herbivores eat producers, carnivores eat other animals and
omnivores eat both.
 Along with producers and decomposers, consumers are part
of what is known as food chains and webs, where energy
and nutrient transfer can be mapped out.
(C) Decomposers or Reducers or detrivores:
 Decomposers are the living component of the ecosystem
that breaks down waste material and dead organisms.
Examples of decomposers include earthworms, dung
beetles and many species of fungi and bacteria.
 The decomposers are known as Saprotrophs (i.e., sapros
= rotten, trophos = feeder).
 They perform a vital recycling function, returning
nutrients incorporated into dead organisms to the soil
where plants can take them up again.
 In this process, they also harvest the last of the sunlight
energy initially absorbed by producers. Decomposers
represent the final step in many of the cyclical ecosystem
processes.
ENERGY FLOW IN ECOSYSTEM
 Every ecosystem has several interrelated mechanisms
that affect human life.
 These are the water cycle, the carbon cycle, the oxygen
cycle, the nitrogen cycle and the energy cycle.
 While every ecosystem is controlled by these cycles, in
each ecosystem its abiotic and biotic features are distinct
from each other.
WATER CYCLE
 Water cycle, also called hydrologic cycle, cycle that
involves the continuous circulation of water in the
Earth-atmosphere system.
 Processes involved in the water cycle, the most
important are:
 Evaporation,

 Transpiration or Condensation,

 Precipitation, and runoff.

 Although the total amount of water within the cycle

remains essentially constant, its distribution among the
various processes is continually changing.
 When it rains, the water runs along the ground and flows into
rivers or falls directly into the sea. A part of the rainwater
that falls on land percolates into the ground. This is stored
underground throughout the rest of the year.
 Water is drawn up from the ground by plants along with the
nutrients from the soil. The water is transpired from the
leaves as water vapour and returned to the atmosphere.
 As it is lighter than air, water vapour rises and forms clouds.
Winds blow the clouds for long distances and when the clouds
rise higher, the vapour condenses and changes into droplets,
which fall on the land as rain.
 Though this is an endless cycle on which life depends, man’s
activities are making drastic changes in the atmosphere
through pollution which is altering rainfall patterns.
 This is leading to prolonged drought periods extending over
years in countries such as Africa, while causing floods in
countries such as the US. El Nino storms due to these effects
have devastated many places in the last few years
CARBON CYCLE
NITROGEN CYCLE
OXYGEN CYCLE
FOOD CHAIN
 The food chain is a straight chain or model that shows the
simple flow of food from one organism to another.
 It starts from a very first producer that are mostly plants and
it flow from one consumer to another and finally ends at the
apex consumer or top predator.
 This predator is not commonly eaten by someone when it dies; it
is decomposed by the decomposers in soil or environment.
 In this way, energy is given back to the environment and its
may be reused by the producers as nutrient or minerals.
 The first organism from which the food chain starts is known as
a producer because it produces its food by itself: like plants
produce food by photosynthesis rather than eating anything
and further organism are named the primary consumers,
secondary consumers, etc. according to their number.
 The length of food chain depends on the number of organisms
involved in it.
 An example of the food chain is as: hawk eats a snake while
snake eats grasshopper which has eaten grass (producer).
FOOD WEB
 A food web is a natural interconnection of food chains and a
graphical representation (usually an image) of what-eats-what in
an ecological community.
 A food web is a system of food chains that are interconnected to
each other at many levels.
 A food web is much larger than the food chain, and it’s not
straight like a food chain. The A food web is also called food cycle.
 Food web includes many populations of producers that are further
eaten by the number of consumers of different communities.
 There are so many consumers eating others at different tropical
level. This food web does not end at a single predator; it has many
top predators in it.
 An example of the food web is as the grass is not only eaten by
grasshopper, it is also eaten by a rabbit or squirrel. Now snake
eats rabbit, squirrel, and the grasshopper, Hawk also eats rabbit
and snake as well. By another side, rabbit and squirrel are also
eaten by a fox, bear, dog, and many other consumers.
 In this way these all food chains interconnected with each other
makes a big food web.
 Food Chain Food Web

A food web is like a

The food chain is network in which many
Definition straight and is small organisms are involved.
and less complex. It is comparatively very
large.

Food chain includes and Food web has many

Producers,
starts from one producer producers, consumers,
Consumers &
and ends at one top and numerous top
Predators
predator. predators.

In the food chain, food In a food web, food flows

Flow flows in a linear in different ways at
pathway. different levels.

A single or separate food

Food web stabilizes the
Stability chain creates instability
ecosystem.
in our ecosystem
ENERGY CYCLE
Tertiary
Consumer

Secondary
Consumer

Primary
Consumer
Primary Producers
FOREST ECOSYSTEM

A forest ecosystem is a community of organisms that lives within a forest.

A forest is usually defined as a large group of trees. However, other
important aspects of a forest are the shrubs, the leaf mulch on the floor
and the plants that live in tandem with the trees.
COMPONENTS OF FOREST ECOSYSTEM:
 Abiotic components: Soil, moisture, air and sunlight.
 Biotic components: Mainly of three types Producers, Consumers, and Decomposers and
transformers.
 Producers: Producers are the green plants of the forest.
They are the main sources of food for all the animals. There are several layers or strata of
vegetation in the forest, namely
1. upper tree stratum,
2. middle tree stratum,
3. lower tree stratum,
4. shrub stratum, and
5. herb and ground stratum. Trees of upper most stratum receive and utilize greater amount
of radiant energy of the sun that those of lower strata. The lower stratum consisting of
herbs, lichens and grasses also manufacture food receiving least amount of light.
 Consumers:
1. Consumer of first order in the forest are grasshoppers, rabbits, deer, monkeys, birds and
many other wild herbivores which take their food directly from plants.
2. Consumer of 2nd order are wolves, jackals etc. which consume the flesh of herbivores.
3. Lions, tigers, hawks are the consumer of top level.

 Decomposer and transformer: They are the micro-organisms living in the forest floor
such as fungi and bacteria which attack the dead bodies of producers and consumers. The
decomposers convert the complex organic materials into simple organic compounds. The
transformers convert the simple organic compounds to simple inorganic forms. Thus, these
free elements again return to the abiotic component and are reutilized by producers.
a) Coniferous Forests grow in the Himalayan mountain region, where the temperatures
are low. These forests have tall stately trees with needlelike leaves and downward
sloping branches so that the snow can slip off the branches. They have cones instead of
seeds and are called Gymnosperms.
b) Broadleaved Forests have several types, such as evergreen forests, deciduous forests,
thorn forests, and mangrove forests. Broadleaved forests have large leaves of various
shapes.
c) Evergreen Forests grow in the high rainfall areas of the Western Ghats, North
Eastern India and the Andaman and Nicobar Islands. These forests grow in areas
where the monsoon lasts for several months. The trees overlap with each other to form
a continuous canopy. Thus very little light penetrates down to the forest floor. Only a
few shade loving plants can grow in the ground layer in areas where some light filters
down from the closed canopy. The forest is rich in orchids and ferns. The barks of the
trees are covered in moss. The forest abounds in animal life and is most rich in insect
life.
d) Wet Evergreen
Wet evergreen forests are found in the south along the Western Ghats and the Nicobar
and Andaman Islands and all along the north-eastern region. It is characterized by
tall, straight evergreen trees that have a buttressed trunk or root on three sides like a
tripod that helps to keep a tree upright during a storm. These trees often rise to a
great height before they open out like a cauliflower. The more common trees that are
found here are the jackfruit, betel nut palm, Jamun, Mango, and Hollock. The trees in
this forest form a tier pattern: shrubs cover the layer closer to the ground, followed by
the short structured trees and then the tall variety. Beautiful fern of various colours
and different varieties of orchids grow on the trunks of the trees.
e) Semi-Evergreen
Semi-evergreen forests are found in the Western Ghats, Andaman and
Nicobar Islands, and the Eastern Himalayas. Such forests have a mixture of the wet
evergreen trees and the moist deciduous trees. The forest is dense and is filled with a
large variety of trees of both types.
f) Deciduous Forests are found in regions with a moderate amount of seasonal
rainfall that lasts for only a few months. Most of the forests in which Teak trees grow
are of this type. The deciduous trees shed their leaves during the winter and hot
summer months. In March or April they regain their fresh leaves just before the
monsoon, when they grow vigorously in response to the rains. Thus there are periods of
leaf fall and canopy re-growth. The forest frequently has thick undergrowth as light can
penetrate easily onto the forest floor.
g) Thorn Forests are found in the semi- arid regions of India. The trees, which are
sparsely distributed, are surrounded by open grassy areas. Thorny plants are called
Xerophytes species and are able to conserve water. Some of these trees have small
leaves, while other species have thick, waxy leaves to reduce water losses during
transpiration. Thorn forest trees have long or fibrous roots to reach water at great
depths. Many of these plants have thorns, which reduce water loss and protect them
from herbivores.
h) Mangrove Forests grow along the coast especially in the river deltas. These plants
are able to grow in a mix of saline and fresh water. They grow luxuriantly in muddy
areas covered with silt that the rivers have brought down. The mangrove trees have
breathing roots that emerge from the mud banks