Download Today we are going to discuss a very important topic namely

Ecosystem
Dr. G. Selva Mangai
Today we are going to discuss a very important topic namely ecosystem and its
components. The term ecosystem we have been hearing since our childhood days but
today we are going to discuss in detail, what are its structural and functional components
of an ecosystem and how are we going to study about the ecosystem and its significance.
Well when we speak about ecosystem it comprises of both the living and the non living
components. How do we define an ecosystem? It is a community of Living and Non
living things together in a specific location. When we speak about Living (Biotic)-Plants,
it includes animals, fungi and bacteria are all biotic or living factors. Non-living
Components (Abiotic) - Abiotic, meaning not alive, are nonliving factors that affect
living organisms. Environmental factors such habitat (pond, lake, ocean, desert, and
mountain) or weather such as temperature, cloud cover, rain, is abiotic factors. So in
detail we are going to study the interaction between the biotic and abiotic components
and what is its significance in its day to day life. So ecology is nothing but the study
about the interaction of organisms with one another and with the environment in which
they occur.
Ecosystem was coined in 1930 by Roy Clapham, to denote the physical and biological
components of an environment considered in relation to each other as a unit.
British ecologist Arthur Tansley later refined the term, describing it as the interactive
system established between biocoenosis (a group of living creatures) and their biotope
(the environment in which they live). We can study the ecology in Individuals,
Population and Community. We will look into each of these in detail.
First when we speak about individual ecosystem, let’s look at this picture. It denotes a
banyan tree. Here we see an individual banyan tree. So if you’re going to study about the
individual banyan tree’s relationship with the surroundings then we call it individual
ecosystem. Individual ecosystem is also called Organismal Ecology (autecology). It is the
study of the life history of an individual (i.e., species) & its response to its environment.
So here in ecosystem there are Species that are all individuals that can potentially breed
with one another and produce viable offspring. Individuals are concerned mostly about
physiology, reproduction, development or behavior. And next we are going to discuss
about population ecology. In the individual ecology we studied about a single banyan tree
and its relationship with the surroundings. Here in population ecology we see a group of
banyan trees. So here in population ecology we are going to study about this group of
banyan trees interactions with the environment. In detail, Population ecology is the study
of the abundance, distribution, productivity, & dynamics of a group of individuals of the
same species. Population is a group of potentially interbreeding & interacting individuals
of the same species living in the same place & time. Populations usually focus on the
habitat and resource needs of individual species, their group behaviors, population
growth, and what limits their abundance or causes extinction. Well now we have seen
about individual ecology and population ecology. Individual ecology deals with a single
species and their interaction with their surroundings and population ecology deals with
the group of the same species belonging to the same community and their interactions
with their surroundings. Well the last one we are going to see now is the community
ecology. What is community ecology? Community ecology is the description &
quantification of natural assemblages of different species/populations. Community is a
collection of species/populations interacting directly and indirectly in the same place &
time. So now we have seen what ecology is. Ecology is nothing but the study of biotic
and abiotic factors in a given surrounding. And we saw who coined the term ecology, and
we have also seen what the three levels are of study in ecology namely individual
ecology, population ecology and community ecology.
Now to study this ecosystem itself there are different levels. We are going to discuss each
one in detail. Now ecosystems are divided into two basic categories.
(i) Terrestrial or land based ecosystems.
(ii) Aquatic ecosystems in water.
If you’re going to study about the components included in the land or the terrestrial
regions and their interactions with the surroundings, we call them as terrestrial or land
based ecosystems. And if you’re going to study about aquatic organisms and their
interactions with the surroundings then it is called aquatic ecosystems in water.
Now what is a very important component about studying this ecosystem is, first of all as
an individual we have to have knowledge of the ecosystem, so as to design an ecosystem
study. So what we have to understand is there are different levels of study and for these
different levels of study we have to have a thorough knowledge of the ecosystem and
their interactions. So we are going to discuss what different levels in understanding the
ecosystem are. Before that we will have to understand that there are two kinds of
ecosystem.
o Natural ecosystems that is already formed on land
o Man modified ecosystems include agricultural land and urban or industrial land
use patterns.
So if we have to understand about ecosystem there are different levels of study. We have
already discussed there are two kinds of ecosystem namely the man made ecosystem and
natural ecosystem.
To study about the understanding of the ecosystem, first of all we will have to have
knowledge about
 What does the ecosystem look like?’
 What is its structure?
 What you should see are its different characteristics.
 What is the composition of its plant and animal species?
 How does the ecosystem work’?
Now we will discuss each of this is detail. First of all look at this picture. You see soil
water, rainfall, distance to permanent water, hydrology, grass nutrients around a
particular area. Now before we go about studying the ecosystem we have to have
knowledge of the soil, water in that particular area, the grass biomass in that particular
area, the grazing angulates in that particular area, the hydrology, soil fertility, everything.
So you have thorough knowledge of their particular area, it will be very easy for us to
study the ecosystem in one particular area. So ecosystem we can study in one particular
area or we can study in different areas too. But having knowledge in that particular area
is important to help us to design that ecosystem. We are going to discuss each thing in
detail. What does the ecosystem look like? One should be able to describe specific
features of the different ecosystems in ones own surroundings. A Field observation is
very important. Take for example, you are residing in an apartment you have to have
knowledge about your car parking area, your roof garden area, etc in your residing place
for you to create an ecosystem in that particular area where you reside. Similarly if we
discuss about the forest area you will have to have the knowledge of grassland, a water
body, an agricultural area, a grazing area, around that particular area. So if you have the
knowledge of that particular area then you will be able to create the structure of an
ecosystem. Well that’s a one point we will have to discuss.
What you should see are its different characteristics. For example, forests, you should
know the kinds of forest, different types of vegetation in pond from periphery to center,
change of vegetation in mountains, etc. What is the composition of its plant and animal
species? For this, you will have to list the well-known plants and animals you can see.
Document their abundance and numbers in nature: very common, uncommon, and rare.
Wild mammals will not be seen in large numbers, cattle would be common. Some birds
are common – which are the most common species? So you should have a thorough
understanding of the ecosystem of that particular area. That is you will have to know
about its structure, its various compositions, various plants and animals in that particular
area.
Next we will see how does the ecosystem work’? The ecosystem functions through
several biogeochemical cycles and energy transfer mechanisms. Once you have
knowledge about this, observe and document the components of the ecosystem which
consists of its biotic and abiotic factors, and then you have to study the interactions
between them. Then we will know how these bio systems works. So all this time in order
to understand the ecosystem we have seen how do we study its different characteristics
and what is its composition of plants and animals in that particular area and how does the
ecosystem look like and what are its structures. Now all this time we have been
discussing on the understanding of the ecosystem. A very important thing we have to
discuss is the degradation of the ecosystem. Now we have seen what is an ecosystem,
how does it interact with each other, what are its different components and how do we go
about finding and understanding ecosystems. A very threatening factor about its
ecosystem is its degradation that results in
 Environmental problem which diminishes the capacity of any species to survive
 Over exploitation of the resources because of rapidly increasing population
 Extinction of plants and animals that can live only in different ecosystem that is
called ’keystone species’
Now because of the increase in population those animals are not able to survive in
that particular ecosystem. So all these are the result of the ecosystem degradation.
Apart from this, degradation also leads to
 Pollution from industry and waste from urban settings
 Forests are deforested for timber, wetlands are drained to create more agricultural
land and semi arid grasslands that are used as pastures are changed into irrigated
fields
What happens is as a result of the ecosystem degradation many of the world’s species
are gravely threatened. Various projections suggest that between 1975 and 2015; from
1 to 11 percent of the world’s species per decade will be committed to extinction. So
it is only in our hands to protect this ecosystem. This is just a pictorial representation
between the ecosystem services and human well being.
So when we speak about ecosystem services to the mankind we see they provide food,
fresh water, wood and fiber and fuel. And regulation of climate regulation, disease
regulation, food regulation, water purifications. Now all these are supporting factors for
mankind. Besides this, when we speak about the constituents of well-being of the
mankind they provide security namely personal safety, secure resource accesses, security
from disasters; basic materials for good life like adequate livelihoods, sufficient nutritious
foods, shelter, access to goods. And with regard to health because of good ecosystem we
have strength, feeling well, access to clean air and water and good social relationships. So
what happens is ultimately when an ecosystem gets affected all these components get
affected. So it is very important that we protect our ecosystem.
This is also the pictorial representation of ecosystem degradation.
So what happened is because of the law of bottomland hard wood forests for example has
affected water quality, increased the risk of floods, and altered the distribution and
abundance of animals that depend on these forests, such as the ivory-billed woodpecker.
So there are series of pictorial representations of the deforestations.
So this is pictorial representation of the Ugly tea shop at Bhojpasa, Garbage strewn in
Gaumukh, Destruction of Juniper, Pilgrims with Birch branches. So what happens as a
result of this degradation? Different problems arise because of the exploitation of natural
resources.
 Deforestation
 Extinction of Species
 Forced Migration
 Soil erosion
 Ozone Depletion
 Water Pollution
 Natural Disaster
This is again an example of the Dead wood of Birch at Bhojapasa, Bhagirathi Peaks.
Well so we have been discussing on the various components of the ecosystem,
understanding of ecosystems, the degradation of the ecosystems. So what is the solution
of all this. Well resource utilization is a very important factor in order to protect these
ecosystems. Now how are we going to protect these resources? Now there are two
models in order to study this resource utilization.
– Exponential Depletion
– Peaked Depletion
Now exponential depletion is the rate of use increases exponentially at a time. That is the
resources used until it is depleted. Take for example, you have a certain important plant
species around your area and until it is completely over we use the resources and after
that we are not able to reproduce it. Next is your peaked depletion. So what do you mean
by peaked depletion. That is the resources increases exponentially for a while in peaks
and again declines. But the resources never get depleted like those of your exponential
depletion. So we have to study the ecosystem resource utilization under these two
categories. One is your exponential depletion and another is your peaked depletion. The
reason for the depletion of natural resources is twofold –
 our rapidly exploding population that needs to sustain itself on
resources
 The growth of affluent societies, which consume
The key to this issue is the need for an ‘equitable’ distribution of all types of natural
resources. A more even sharing of resources within the community can reduce these
pressures on the natural ecosystems.
Fine, now we will have to study about the structure and the functions of the ecosystem in
order to utilize these particular resources. Now how should we study the structure and
function of an ecosystem or what are its different components. By Architecture or
Structure of an Ecosystem, we mean
 The composition of biological community including species, numbers, biomass,
life history and distribution in space, etc.
 The quantity and distribution of non living materials like nutrients, water etc.
 The conditions of existence such as temperature, light etc. An ecosystem
possesses both living components or biotic factors and non living or abiotic
factors.
Components that make up the structural aspects of an ecosystem include:
1) Inorganic aspects – C, N, CO2, H2O.
2) Organic compounds – Protein, Carbohydrates, Lipids – link abiotic to biotic aspects.
3) Climatic regimes – Temperature, Moisture, Light & Topography.
4) Producers – Plants.
5) Macro consumers – Phagotrophs – Large animals.
6) Micro consumers – Saprotrophs, absorbers fungi
Then when we speak about the function of an ecosystem we study them under three
categories namely
 Trophic level interaction
 Ecological succession
 Biogeochemistry
Now what comes under your functional aspects are your
1) Energy cycles.
2) Food chains.
3) Diversity-inter linkages between organisms.
4) Nutrient cycles-biogeochemical cycles.
5) Evolution
Trophic Level Interaction deals with how the members of an ecosystem are connected
based on nutritional needs. Ecological Succession deals with the changes in
features/members of an ecosystem over a period of time. Biogeochemistry is focused on
the cycling of essential materials in eco system. This is an example of your sample food
chains which deals with the trophic level.
It goes like there are primary producers and from the primary producers goes to the
secondary consumers, tertiary consumers and quaternary consumers. So these are
different examples of the grassland biome, ocean biome and the pond biome. When we
speak about grassland biome, first the primary producer here is the grass, the primary
consumer is the grasshopper, it is again consumed by rats, again it’s consumed by the
snakes, again its consumed by the hawks. So this is just a simple example of your trophic
level interactions.
When we speak about energy flow, it is like the energy flows through the ecosystem in
one direction which is called the food chain. It’s like a pyramid. At the bottom you have
the producers and then your consumers. The producers contain the most energy and they
are the autotrophs and manufacture their own food. Next you have the consumers. These
consumers they obtain the energy by eating the producers are heterotrophes. There will
usually be several levels of consumers beginning with herbivores and then to carnivores
and the omnivores. Finally they decompose and they obtain the energy from the waste
and dead organisms. Examples are like those of your bacteria and fungi. So from the
sunlight that is from the producers it goes to the consumers and in consumers there are
many levels. As we move up each level, the energy level also decreases. Take for
example; in grass the producer has 1000 kilo calories. The grass is eaten by the mice or
the rats; the amount of calories gets reduced to 100 kilo calories. So when these mice or a
rat is eaten by the ferrets the energy again gets reduced to 10 kilo calories. The ferrets are
then eaten by owls then and finally the energy gets reduced to 1 kilo calories. So this is
how the energy dissipates in a food chain.
Now apart from food chain the energy flow also constitutes various cycles.
 Carbon cycle
 Nitrogen cycle
 Oxygen cycle
When we speak about nitrogen cycle, mainly the nitrogen is being utilized by the plants
for the fixation of atmospheric nitrogen. This is a pictorial representation of the nitrogen
cycle. Nitrogen in the atmosphere is being fixed by the nitrogen fixing bacteria with the
help of the root nodules in the legumes plants. Now what happens is this nitrogen fixing
soil bacteria converts the ammonium into nitrates. So this process is called as
amonification, conversion of ammonium into nitrates with the help of nitrifying bacteria,
it is called as amonification. Next these nitrates are again converted to nitrites with the
help of nitrifying bacteria and these nitrites are used by the plants in order to fix the
nitrogen. So this entire nitrogen is important for the plants to fix the nitrogen in the
atmosphere.
Next we are going to see about the carbon cycle. This carbon cycle is said to biogeo
chemical process by which carbon undergoes chemical reaction, changes forms and
moves through the different reservoirs including living organisms. Now this is a pictorial
representation of the carbon cycle in different reservoirs like those of soil carbon,
microbial respiration and decomposition in ocean sediments, etc. so carbon is also a very
important component like those of the nitrogen.
Next is the oxygen cycle. The Oxygen cycle is the biogeochemical cycle that describes
the movement of oxygen within its three main reservoirs:
 The atmosphere (air)
 The total content of biological matter within the biosphere (the global sum of all
ecosystems)
 The lithosphere (Earth's crust).
So this is a pictorial representation of the oxygen cycle reservoirs and its flux in
lithosphere, in biosphere which is again used for respiration and in decay, again this
oxygen is used in the photolysis, weathering, etc.
So all this time we have been discussing on the ecosystem, its various components, how
do we understand the ecosystem and how do we construct the ecosystem and we have
been studying about the ecosystem and what are the threatening factors of the ecosystem.
To sum up if you have to really constitute a good ecosystem what is our contribution to
the society. First of all we have to understand
 What is the nature of the ecosystem?
 What is its structure and its functions?
 Who uses the ecosystem and for what purpose?
 How are these ecosystems degraded?
 What can be done to protect it from deteriorating in the long-term?
So as I said in the beginning of my talk one impulse from a vernal wood would may teach
you more of men than all sages can. So it is only in our hands to protect this mother
nature. Each and every individual should take the responsibility that we have to constitute
a good ecosystem for both the abiotic factors and the biotic factors to survive in a
particular surrounding. To conclude we will have to understand what is an ecosystem and
its various components and how do we constitute a very good ecosystem and with this
knowledge how are we going to protect this resource and finally structure and study the
functions of this particular ecosystem for the survival of the mankind. Thank you.