ecosystem by sanket

8/4/2019 Ecosystem by Sanket

1/12

Ecosystems

Sanket Jadhav [T.E. EXTC] 1

Introduction:

An ecosystem can be defined as 'a structural and functional unit of biosphere or segment of

nature consisting of community of living beings and the physical environment, both interacting and

exchanging materials between them'.

Ecosystems are dynamic entities composed of the biological community and the abiotic

environment. An ecosystem's abiotic and biotic composition and structure is determined by the state

of a number of interrelated environmental factors. Changes in any of these factors will result indynamic changes to the nature of these systems. For example, a fire in the temperate deciduous forest

completely changes the structure of that system. There are no longer any large trees, most of the

mosses, herbs, and shrubs that occupy the forest floor are gone, and the nutrients that were stored in

the biomass are quickly released into the soil, atmosphere and hydrologic system. After a short time

of recovery, the community that was once large mature trees now becomes a community of grasses,

herbaceous species, and tree seedlings.

The simplest level of organization in Ecosystem is that of the organism. An organism refers

to a particular organism in an ecosystem, say cat, dog etc. A population includes all the members of

the same organism that live in one place at one time. All the different populations that live in aparticular area make up a community. The physical location of a Community is called the habitat.

Ecosystem is in turn a level of organization and has one higher level of organization called

biosphere. The photograph on the next page derived from a foreign ecology book would clearly

illustrate the various levels of organization.

The diversity of an ecosystem is a measure of the number of different species there, and how

common each species is. Ecosystems are very complex. They can contain hundreds or even

thousands of interacting species. Each organism or species in the community has a role or profession

in that community and in ecology this is the organisms niche.


2/12

Ecosystems


Classification of Ecosystem:

An ecosystem can be classified as below

There are further classifications in the above chart, but for a beginner level, it is enough to

concentrate on these areas. Also the study of artificial ecosystem is not the scope of an

environmental scientist. The environmentalists deal with natural creations and management only.

Moreover the system in artificial ecosystem does not offer much to study. Therefore we are more

interested in natural ecosystem and dont consider artificial ecosystem

Approach to Ecosystem:

With an ecosystem comprising of large number ofspecies, it would seem and is impractical

to study the interaction of each organism with another, it is impossible to approach an ecosystem by

studying the individual organism environment relationship. Therefore we study an ecosystem

following a wholesome approach.

We study the ecosystems by studying the two aspects (attributes) of an ecosystem. They are

Structure or Architectural Process

Function or Working Process

Both processes help to understand the concept of ecosystem in simplified manner.

The architectural process classifies ecosystem into biotic and abiotic components while the

working process help to understand the interaction of ecosystem components at different levels.

Let us understand more about these approaches to understand Ecosystem.

ECOSYSTEM

NATURAL ECOSYSTEM ARTIFICIAL ECOSYSTEM

TERRESTRIAL

ECOSYSTEM

Forests

Grasslands

Deserts

AQUATIC

ECOSYSTEM

Fresh Waters

Marine Waters


3/12

Ecosystems


STRUCTURE OF AN ECOSYSTEM

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 and biotic factors and nonliving or abiotic

factors.

The nonliving factors, called abiotic factors, are physical and chemical characteristics of the

environment. They include solar energy (amount of sun light), oxygen, CO2, water, temperature,

humidity, ph, and availability of nitrogen.

The living components of the environment are called Biotic Factors. They include all the

Living Things that affect an organism. Biotic Components are often categorized as Producers,

Consumers, and Decomposer.

The structure of an ecosystem can be represented as below:

ECOSYSTEM

ABIOTIC COMPONENTS BIOTIC COMPONENTS

CLIMATIC

FACTORS

E.g. Rain

LightWind

Temp.

EDAPHIC

FACTORS

E.g. Soil

MineralsOxygen

Topography

PRODUCERS

also known as

autotrophs,

they produceenergy

CONSUMERS

also known as

heterotrophs,

they consumeand transfer

energy

DECOMPOSERS

better known as

reducers or

saptrotrophsrecycle energy


4/12

Ecosystems


FUNCTION OF AN ECOSYSTEM

The function of an ecosystem is a broad, vast and often confused topic. The function of an

ecosystem can be best studied by understanding the history of ecological studies. The function of an

ecosystem can be studied under the three heads.

1. Trophic Level Interaction

2. Ecological Succession

3. Biogeochemistry

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 upon the cycling of essential materials

in an ecosystem.

Trophic Level Interaction was developed by zoologist Charles Elton. It deals with who eats

who and is eaten by whom in an ecosystem. The study of trophic level interaction in an ecosystem

gives us an idea about the energy flow through the ecosystem.

The trophic level interaction involves three concepts namely

1. Food Chain

2. Food Web

3. Ecological Pyramids

Food Chain:

In an ecosystem one can observe the transfer or flow of energy from one trophic level to other in

succession. A trophic level can be defined as the number of links by which it is separated from the

producer, or as the position of the organism in the food chain. The patterns of eating and being eaten

forms a linear chain called food chain which can always be traced back to the producers. Thus,

primary producers trap radiant energy of sun and transfer that to chemical or potential energy oforganic compounds such as carbohydrates, proteins and fats.

When an herbivore animal eats a plant (or when bacteria decompose it) and these organic

compounds are oxidized, the energy liberated is just equal to the amount of energy used in

synthesizing the substances (first law of thermodynamics), but some of the energy is heat and not

useful energy (second law of thermodynamics). If this animal, in rum, is eaten by another one, along

with transfer of energy from a herbivore to carnivore a further decrease in useful energy occurs as

the second animal (carnivore) oxidizes the organic substances of the first (herbivore or omnivore) to

liberate energy to synthesize its own cellular constituents. Such transfer of energy from organism to

organism sustains the ecosystem and when energy is transferred from individual to individual in a


5/12

Ecosystems


particular community, as in a pond or a lake or a river, we come across the food chains. The number

of steps in a food chain is always restricted to four or five, since the energy available decreases with

each step. Many direct or indirect methods are employed to study food chain relationships in nature.

They include gut content analysis, use of radioactive isotopes, precipitin test, etc.

A food chain always begins with the producer and follows the flow of energy through severallevels of consumers. The first order consumers are herbivores who consume producers.

The second order consumer feed on the first order consumers, etc.

In nature, basically two types of food chains arc recognized grazing food chain and

detritus food chain.

Grazing food chain: This type of food chain starts from the living green plants goes to grazing

herbivores and on to the carnivores. Ecosystems with such type of food chain are directly dependent

on an influx of solar radiation. Most of the ecosystems in nature follow this type of food chain.


6/12

Ecosystems


Detritus food chain: The organic wastes, exudates and dead matter derived from the grazing

food chain are generally termed detritus. The energy contained in this detritus in not lost to the

ecosystem as a whole; rather it serves as the source of energy for a group of organisms (Detritivores)

that are separate from the grazing food chain, and generally termed as the detritus food chain

Significance of food chain: The food chain studies/help under stand the feeding relationships

and the interaction between organisms in any ecosystem. They also help us to appreciate the energy

flow mechanism and matter circulation in ecosystem, and understand the movement of toxic

substances in the eco-system and the problem of biological magnification

Food Web:

In nature simple food chains occur rarely the same organism may operate in the ecosystem at

more than one trophic level i.e it may derive its food from more than one source. Even the sameorganism may be eaten by several organisms of a higher trophic level or an organism may feed upon

several different organisms of a lower trophic level. Usually the kind of food changes with the age of

the organism and the food availability. Thus in a given ecosystem various food chains are linked

together and interested each other to form a complex network called food Web. Generally food webs

are not too complex. Expect in insect communities, omnivores are scare and when they occur they

usually feed on species in adjacent trophic levels. Within habitats, food webs arc rarely broken up

into discrete compartments. The number of species of predators in a food web typically exceeds the

number of species of prey by an average of 1.3 predator species per prey species.

A more complex food web. Notice that all organisms have arrows connecting to the decomposers.


7/12

Ecosystems


Ecological Pyramids:

Another model, of energy flow through an ecosystem is the trophic pyramid. The purpose of

a trophic pyramid is to graphically represent the distribution of biomass or energy among the

different trophic levels of the ecosystem. A trophic level is the position of an organism in an

ecosystem (producer, first order consumer, etc). A pyramid is used as the model because it shows the

decrease in energy available as you go through a food web. The availability of energy decreases as

you travel up the pyramid because only 10% of energy absorbed becomes stored energy (available to

transfer). The other 90% of energy is mostly lost as heat from metabolic processes and maintenance

of daily life functions.

A typical trophic pyramid showing the decrease in energy available as movefrom one level to the next.

In the successive steps of food chain the number and mass of the organisms in each step is

limited by the amount of energy available. Since some energy is lost as heat, in each transformation

the steps become progressively smaller near the top. This relationship is sometimes called ecological

pyramid. The ecological pyramids represent the trophic structure and also trophic function of the

ecosystem. In many ecological pyramids, the producer form the base and the successive trophic

levels make up the apex.


8/12

Ecosystems


Energy Flow in the Ecosystem:

Energy flows through an ecosystem and is ultimately lost to the environment. Matter, on the

other hand, is recycled. Matter is finite. If matter was not cycled through the ecosystem, the supply

would have been exhausted a long time ago. A simple matter cycle consists of an exchange of matterbetween living and non-living components of an ecosystem. Organisms incorporate various elements

(compounds) from the environment into their bodies. When these organisms die, their bodies are

broken down by decomposers and the compounds are released into the environment.

Water Cycle:

The Water Cycle

The water cycle, also called the hydrologic cycle, follows the continuous path of water.

Water enters the vapor phase through evaporation and transpiration (the release of water vapor from

plants and animals). The sun is the main source of energy that allows the water to undergo a phase

change. The water vapor raises, cools, and condenses forming clouds. The water droplets become

heavier and eventually fall as precipitation. A small portion of the precipitation will be taken up by

the plants and animals more will infiltrate the soil, entering the water table, with the largest portion

of the precipitation forming runoff on the surface of the land to drain into streams, rivers, lakes, and

ultimately the ocean. The hydrologic cycle is a continuous process that recycles all the water on the

planet.


9/12

Ecosystems


Carbon Cycle:

The Carbon Cycle

Carbon dioxide makes up only 0.03% of the atmosphere but is the major source of carbon for

additional biomass. Carbon dioxide is converted to organic carbon by photosynthesis in green plants.

Organic carbon is then available to travel through the food web to eventually be released back to the

atmosphere by cellular respiration and decomposition. Fossil Fuels are another link in the carbon

cycle. Organic carbon has been trapped underground for millions of years in the form of coal, oil,

and natural gas. This carbon, in the form of carbon dioxide, is released back to the atmosphere by the

burning of fossil fuels. Carbon dioxide that is dissolved in the ocean can be absorb by animals and

temporarily trapped in their skeletons and shells. It should be noted that humans are altering the

carbon cycle with the increased use of fossil fuels.


10/12

Ecosystems


Nitrogen Cycle:

The Nitrogen Cycle

Nitrogen comprises approximately 80% of the atmosphere but is not accessible to most life

forms. It must be fixed before it can be absorbed. Nitrogen-fixing bacteria are responsible for

converting atmospheric nitrogen into its ionic form, ammonium. Ammonium is converted to nitrites

and nitrates. Plants can access this nitrate. However, animals must get their nitrogen from the food

that they eat. Thus, nitrogen flows through the food web much like carbon. Nitrogen is returned back

to the atmosphere through decomposers and then denitrifying bacteria.


11/12

Ecosystems


Oxygen Cycle:

The Oxygen Cycle

The oxygen cycle is very similar to the carbon cycle, but in reverse. Oxygen comprises

approximately 20% of the atmosphere. Oxygen is removed from the atmosphere through cellular

respiration and returned to the atmosphere by photosynthesis. Large amounts of oxygen are dissolved

in large bodies of water.


12/12

Ecosystems


Ecological Imbalance - Imperiling the Ecosystem:

With the increased industrialization and scientific approach to our life, the natural resources

and rich natural heritage which were being preserved for centuries have begun dwindling greatly.

Any kind of imbalance in nature results into severe danger to our ecosystem.

Its treatment with nature has posed today many serious challenges and problems like climate

change, vector-borne disease, decay in wildlife and its resources and food and water shortage.

Exploitation of natural resources prevalent all over the world has erupted into severe ecological

degradation, which is definitely the biggest threat to proper functioning of our ecosystem.

Biodiversity & Ecosystem Conservation:

Biodiversity and ecosystems sustain each other. They are the living natural capital on which

human beings, as one species among others, depend for existence and well-being. Biodiversity and

ecosystems are the natural basis for the development of sustainable resource uses, including forestry,

farms, renewable energy, urban land use, fisheries and other coastal & marine uses.

Proactive programs to conserve biodiversity include research and management for wild

populations and habitats, protected areas, large ecosystems such as Great Lakes, grasslands, forests,wetlands, deserts, major rivers and estuaries, oceans, and more sustainable resource practices. They

also include planning, monitoring and enforcement related to land, sea and resource uses,

environmental assessment, pollution and species at risk.

The need for conservation action is urgent, nationally and globally. The last two centuries

have seen increasing rates of depletion of natural capital, with resulting changes increasingly evident

even at global levels, such as climate change, large ecosystem fragmentation and degradation, and

species extinctions. There is now a higher level of multilateral and national fora and talk for

conservation, but the negative momentum is as yet only barely affected.

ecosystem by sanket

Documents