Essay on Ecosystem: Top 7 Essays on Ecosystem | Geography

Here is a compilation of essays on ‘Ecosystem’ for class 6, 7, 8, 9, 10, 11 and 12. Find paragraphs, long and short essays on ‘Ecosystem’ especially written for school and college students.

Essay on Ecosystem

Essay Contents:

1. Essay on the Meaning of Ecosystem
2. Essay on the Concept of Ecosystem
3. Essay on the Types of Ecosystem
4. Essay on the Structure of Ecosystem
5. Essay on the Components of Ecosystem
6. Essay on the Properties of Ecosystem
7. Essay o the Functioning of Ecosystems

Essay # 1. Meaning of Ecosystem:

The term ‘ecosystem’ was first used by A.G. Tansley in 1935 who defined ecosystem as ‘a particu­lar category of physical systems, consisting of organ­isms and inorganic components in a relatively stable equilibrium, open and of various sizes and kinds’.

According to Tansley the ecosystem is comprised of two major parts viz., biome (the whole complex of plants and animals of a particular spatial unit) and habitat (physical environment) and thus ‘all parts of such an ecosystem-organic and inorganic, biome and habitat-may be regarded as interacting factors which, in a mature ecosystem, are in approximate equilib­rium, it is through their interactions that the whole system is maintained’. F.R. Fosberg (1963) has defined ecosystem as ‘a function­ing, interacting system composed of one or more living organisms and their effective environment, both physical and biological’.

According to R.L. Linderman (1942) the term ecosystem applies to ‘any system composed of physical-chemical-biological processes, within a space-time unit of any magnitude’. In E.P. Odum’s view (1971)’living organisms and their non-living (aboitic) environment are inseparably interrelated and interact upon each other.

Any unit that includes all of the organisms (i.e., the community) in a given area interacting with the physical environment so that a flow of energy leads to clearly defined trophic struc­ture, biotic diversity and material cycle (i.e., exchange of materials between living and non-living parts) within the system is an ecological system or ecosystem’.

According to A.N. Strahler and A.H. Strahler (1976). “The total assemblage of components interacting with a group of organisms is known as ecological system or more simply, an ecosystem. Ecosystems have inputs of matter and energy, used to build biological structure (the biomass), to produce and to maintain necessary internal energy levels. Matter and energy are also exported from an ecosystem. An ecosystem tends to achieve a balance of the various processes and activi­ties within it”.

Based on the contents of above definitions of ecosystem provided by various scientists it may be pointed out that ‘ecosystems are, therefore, unities of organisms connected to one another and to their envi­ronment’ and the ecosystem is, thus, the sum of all natural organisms and substances within an area, and it can be viewed as a basic example of an open system in physical geogra­phy’. Stressing the importance of ecosystem C. C. Park further says that ‘ecosystems are regarded by many ecologists to be the basic units of ecology because they are complex, interdependent and highly organized systems and because they are the basic building blocks of the biosphere’.

In a more lucid style and simple term an ecosys­tem may be defined as a fundamental functional unit occupying spatial dimension of ‘earth space ship’ characterised by total assemblage of biotic community and abiotic components and their mutual interactions within a given time unit.

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Essay # 2. Concept of Ecosystem:

According to Eugene P. Odum (1983), “any unit (a bio-system) that includes all the organisms that function together (the biotic com­munity) in a given area interacting with the physical environment so that a flow of energy leads to clearly defined biotic structures and cycling of materials between living and non-living parts is an ecological system or ecosystem”. Thus, ecosystem is the basic functional unit in ecology, as it includes both organisms and biotic environment, each influencing the properties of the other and both are neces­sary for the maintenance of life.

Ecosystems have both structure and function.

The structure part comprises of:

(i) The composition of all the biological com­munities,

(ii) The distribution and quantity of all the non-living materials (nutrients, water etc.) and

(iii) The conditions of existence (temperature, light etc.).

The functional part consists of:

(i) The energy flow in the community,

(ii) The nutrient cycles, and

(iii) Ecologi­cal and biological regulations (photoperiodism, nitrogen fixing organisms etc.).

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Essay # 3. Types of Ecosystem:

Ecosystems may be identified and classified on various bases, with different purposes and objectives as outlined below:

(1) On The Basis of Habitats:

The habitats ex­hibit physical environmental conditions of a particular spatial unit of the biosphere. These physical conditions determine the nature and characteristics of biotic communities and therefore there are spatial variations in the biotic communities.

Based on this premise the world ecosystems are divided into two major categories viz.:

(A) Terrestrial ecosystems, and

(B) Aquatic ecosystems.

There are further variations in the terrestrial ecosystems in terms of physical conditions and their responses to biotic communities.

Therefore, the terrestrial ecosys­tems are further divided into sub-categories of:

(i) Upland or mountain ecosystems,

(ii) Lowland ecosystems,

(iii) Warm desert ecosystems, and

(iv) Cold desert ecosys­tems.

These sub-ecosystems may be further divided into descending orders depending on specific purposes and objectives of studies.

(B) The aquatic ecosystems are subdivided into two broad categories:

(i) freshwater (on continents) ecosystems and

(ii) marine ecosystems. Freshwater ecosystems (Bi) are further divided into (Bia) river ecosystems, (Bib) marsh and bog ecosystems while (Bii) marine ecosystems are divided into (Biia) open ocean ecosystems, (Biib) coastal estuarine ecosys­tem, (Biic) coral reef ecosystem, or can be alternatively divided into (Biia) ocean surface ecosystems, (Biib) ocean bottom ecosystems.

(2) On the basis of spatial scales:

Ecosystems are divided into different types of various orders on the basis of spatial dimensions required for specific pur­poses.

The largest ecosystem is the whole biosphere which is subdivided into two major types:

(A) Continen­tal ecosystems, and

(B) Oceanic or marine ecosystems.

The spatial scales may be brought down from a conti­nent to a single biotic life (plant or animal).

(3) On The Basis of Uses:

E.P. Odum (1959) has divided the world ecosystems on the basis of use of harvest methods and net primary production into two broad categories viz.:

(A) cultivated ecosystems and

(B) non-cultivated or natural ecosystems.

Cultivated eco­systems may be further subdivided into several catego­ries on the basis of cultivation of dominant crops e.g., wheat field ecosystem, rice field ecosystem, sugarcane field ecosystem, fodder field ecosystem etc. Similarly, non-cultivated ecosystems can be subdivided into forest ecosystem, tall grass ecosystem, short grass ecosystem, desert ecosystem, see-weeds ecosystem etc.

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Essay # 4. Structure of Ecosystem:

Interaction of biotic and abiotic components results in physical structure that is the characteristic of each type of ecosystem.

The two important structural features of an ecosystem are:

(i) Species composition:

It is the identification and enumeration of plant and animal species of an ecosystem.

(ii) Stratification:

It is the vertical distribution of different species occupying different levels in ecosystem, e.g., trees occupy top vertical strata or layer of the forest, shrubs occupies the second and herbs and grasses occupy the bottom layers.

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Essay # 5. Components of Ecosystem:

Ecosystem has two major components (Table 4.1):

I. Abiotic Component:

The abiotic components of an ecosystem comprises of all the non-living factors. It includes light; temperature; climate; pressure; all the inorganic substances (Phosphorus, Sulfur, Carbon, Nitrogen, Hydrogen etc.) present in water, soil and air involved in mate­rial cycles; organic compounds (proteins, car­bohydrates, lipids etc.) that link the abiotic and biotic components of the ecosystem.

II. Biotic Component:

The biotic factors include the living organisms of the environment. They form the trophic structure (trophe, nourishment) of any ecosystem, where living organisms are dis­tinguished on the basis of their nutritional relationships. From this standpoint, an ecosystem is two-layered:

(a) Autotrophic (self-nourishing) compo­nent:

This is the upper stratum and is often referred to as the “green belt”. It comprises of the chlorophyll-containing plants, photosynthetic bacteria, chemosynthetic microbes, etc. They use simple inorganic substances along with the fixation of light energy, for the buildup of complex organic substances and are thus known as producers.

(b) Heterotrophic (other-nourishing) com­ponent:

This is the lower stratum or ‘brown belt” of soils and sediments, decaying matter, roots etc. Here utilisation, rearrangement and decomposition of complex materials are the main features. As these organisms eat or con­sume other organisms, they are known as consumers.

The consumers are categorized into:

(i) Macro-consumers:

Macro-consumers or phagotrophs (phago, to eat) are chiefly ani­mals that consume other organisms or partic­ulate organic matter. These organisms are further divided into primary, secondary and tertiary consumers. Herbivores that depend upon plant food are known as primary con­sumers. Secondary and tertiary consumers, when present, are either carnivores or omnivores.

(ii) Micro-consumers:

Micro-consumers or saprotrophs (sapro, to decompose) or decomposers or osmotrophs (osmo, to pass through a membrane) are chiefly bacteria and fungi, that obtain their food (energy) either by break-down of dead tissues or by absorbing dissolved organic matter extruded by or extracted from plants or other orga­nisms.

The saprotrophs by their decomposing activity:

1. Release inorganic nutrients that can be used by the producers.

2. Provide food for the macro-consu­mers.

3. Excrete hormone-like substances that inhibit or stimulate other biotic components of the ecosystem.

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Essay # 6. Properties of Ecosystem:

The following are the basic properties of an ecosystem:

(i) Ecosystem of any given space-time-unit rep­resents the sum of all living organisms and physical environment.

(ii) It is composed of three basic components viz., energy, biotic (biome) and abiotic (habitat) com­ponents.

(iii) It occupies certain well defined area on the earth-space ship (spatial dimension).

(iv) It is viewed in terms of time-unit (temporal dimension).

(v) There are complex sets of interactions be­tween biotic and abiotic components (including en­ergy component) on the one hand and between and among the organisms on the other hand.

(vi) It is an open system which is charaterised by continuous input and output of matter and energy.

(vii) It tends to be in relatively stable equilib­rium unless there is disturbance in one or more control­ling factors (limiting factors).

(viii) It is powered by energy of various sorts but the solar energy is the most significant.

(ix) It is a functional unit wherein the biotic components (plants, animals including man and mi­cro-organisms) and abiotic (physical environment) components (including energy component) are inti­mately related to each other through a series of large- scale cyclic mechanisms viz. energy flow, water cycle, biogeochemical cycle, mineral cycle, sediment cycle etc.

(x) Ecosystem has its own productivity which is the process of building organic matter based on the availability and amount of energy passing through the ecosystem. The productivity refers to the rate of growth of organic matter in an areal unit per time-unit.

(xi) Ecosystem has scale dimension i.e., it varies in spatial coverage. It may be as small as a cowshed, a tree or even a part of a tree having certain micro­organisms. The largest unit is the whole biosphere. Thus, the ecosystems may be divided into several orders on the basis of spatial dimension. It is clear that ‘the ecosystem is a convenient scale at which to con­sider plants and animals and their interaction because it is more localised and thus more specific than the biosphere in its entirety, and it includes a sufficient wide range of individual organisms to make regional generalizations feasible and valuable’.

(xii) There are different sequences of ecosystem development. The sequence of ecosystem develop­ment in terms of a particular suite of physical and chemical conditions is called as ‘sere’. A ‘sere’ repre­sents the development of a series of sequential successions starting from primary succession and cul­minating into the last succession in a sere as ‘climax’ or ‘climatic climax’ which is the most stable situation of an ecosystem. Thus, the study of ecosystem devel­opment may help in environmental planning from ecological point of view.

(xiii) Ecosystems are natural resource systems.

(xiv) Ecosystem concept is monistic in that envi­ronment (abiotic component), man, animals, plants and micro-organisms (biotic component) are put together in a single formwork so that it becomes easy to study the patterns of interactions among these components.

(xv) It is structured and well organised system.

(xvi) Ecosystem, for convenience, may be stud­ied as a ‘black box model’ by concentrating on the study of input variables and related output variables while the internal variables may be-ignored to reduce the complexity.

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Essay # 7. Functioning of Ecosystems:

The functioning of an ecosystem depends on the pattern of energy flow because all aspects of living components of an ecosystem depend on energy flow which also helps in the distribution and circulation of organic and inorganic matter within the ecosystem. While the energy flow follows unidirectional path, the circulation of matter follows cyclic paths.

Here, only a brief discussion is presented so as to have a general idea of the functioning of ecosystem.

The energy pattern and flow are governed by first and second laws of thermodynamics. The first law states that in any system of constant mass, energy is neither created nor destroyed but it can be transformed from one type to another type (example, electrical energy can be converted into mechanical energy). In terms of ecosystem energy inflow or energy input into the system will be balanced by energy outflow from the system.

The second law of thermodynamics states that when work is done, energy is dissipated and the work is done when one form of energy is transformed into another form. In the context of ecosystem there is dissipation of energy from each transfer point (trophic level) and thus the dissipated or lost energy is not again available to the ecosystem.

Solar radiation is the basic input of energy entering the ecosystem. The radiant solar energy is received by the green plants. Most of the received solar energy is converted into heat energy and is lost from the ecosystem to the atmosphere through plant com­munities. Only a small proportion of radiant solar energy is used by plants to make food through the process of photosynthesis.

Thus, green plants trans­form a part of solar energy into food energy or chemi­cal energy which is used by the green plants to develop their tissues and thus is stored in the primary producers or autotrophs at the bottom of trophic levels. The chemical energy stored at trophic level one becomes the source of energy to the herbivorous animals at trophic level two of the food chain.

Some portion of energy is lost from trophic level one through respira­tion and some portion is transferred to plant-eating animals (herbivores) at trophic level two. The transfer of energy from trophic level one (green plants) to trophic level two (herbivores) is performed through the intake of organic tissues (which contain potential chemical energy) of green plants by the herbivores.

Thus, the chemical energy consumed by herbivores helps in the building of their own tissues and is stored at trophic level two and becomes the source of energy for carnivores at trophic level three. A substantial portion of chemical energy is released by carnivores at trophic level three through respiration because more energy is required for the work to be done by carni­vores at trophic level three (building of tissues, grow­ing, movement for grazing, catching prey, reproduc­tion of their off-springs etc.).

Some portion of potential chemical energy is transferred from trophic level three to trophic level four or top trophic level represented by omnivores (those animals which eat both plants and animals, man is the most important example of omni­vores). The animals at trophic level four mainly man also take energy from trophic levels one and two. Again some portion of energy is released by omnivores through respiration.

The remaining stored chemical energy in the plants and animals is transferred to decomposers when they (plants and animals) become dead. The decomposers release substantial amount of energy through respiration to the atmosphere. It may be pointed out that at each trophic level the available potential chemical energy to be transferred to the next higher trophic level decreases as more energy is re­leased through respiration to the atmosphere from each trophic level.

Respiration means chemical breakdown of food in the body and thus respiration releases heat which is transferred to the atmosphere. Based on above statement it may be summarized that apart from the energy released to the atmosphere through respiration, the remaining energy is transferred in successive con­sumer stages known as trophic (literally nourishment) levels from autotrophs to heterotrophs (meaning that they derive their nourishment from others). Ultimately all the energy is passed on the detrivores, or decomposer organisms’

The circulation of elements or matter or nutri­ents (organic and inorganic both) is made possible through energy flow. In other words, energy flow is the main driving force of nutrient circulation in the various biotic components of the ecosystem.

The organic and inorganic substances are moved reversibly in the bio­sphere, atmosphere, hydrosphere and lithosphere through various closed system of cycles in such a way that total mass of these substances remain almost the same and are always available to biotic communities.

‘In other words, the materials that make up the biosphere are distributed and redistributed by means of an infinite series of cyclic pathways motored by the continuous input of energy’ .

The materials or nutrients involved in the circulation within an ecosystem are grouped into three categories viz.:

(i) Macro-elements (which are required in large quantity by plants, e.g., oxygen, car­bon and hydrogen),

(ii) Minor or micro- elements (which are required by plants in relatively large amounts e.g., nitrogen, phosphorous, potassium, calcium, mag­nesium and sulphur) and

(iii) Trace elements (plants require very small amounts of about 100 elements, important being iron, zinc, manganese and cobalt).

Besides these inorganic chemical elements, there are organic materials as well which comprise:

(i) Decom­posed parts of either alive or dead plants and animals, and

(ii) Waste materials released by animals.

A few of the chemical elements act as organic catalysts or en­zymes because they help chemical reactions but sel­dom undergo chemical change themselves.

Such chemi­cal elements are hydrogen, oxygen and nitrogen which belong to gaseous phase (that is they are found in the atmosphere in gaseous state-atmospheric reservoir or pool) and phosphate, calcium or sulphur which belong to sedimentary phase (that is they are found in weath­ered rocks and soils-sedimentary reservoirs or pool).

Thus, these elements, derived from atmospheric and sedimentary reservoirs, are pooled into soils from where these are taken by plants in solution form though the process of root osmosis. The plants then convert these elements into such forms which are easily used in the development of plant tissues and plant growth by biochemical processes (generally photosynthesis). Thus, the nutrients driven by energy flow pass into various components of biotic communities through the process known as ‘biogeochemical cycles’.

In a generalised form the biogeochemical cycles include the uptake of nutrients or inorganic elements by the plants through their roots in solution form from the soils where these inorganic elements, derived from sedimentary phase, are stored. The nutrients are transported to various trophic levels through energy flow. Here, the nutrients become organic matter and are stored in the biotic reservoirs of organic phase.

The organic elements of plants and animals are released in a variety of ways i.e.:

(i) Decomposition of leaf falls from the plants, dead plants and animals by decomposers and their conversion into soluble inor­ganic form.

(ii) Burning of vegetation by lightning, accidental forest fire or deliberate action of man. The portions of organic matter on burning are released to the atmosphere and these again fall down, under the impact of precipitation, on the ground and become soluble inorganic form of element to join soil storage, while some portions in the form of ashes are decom­posed by bacterial activity and join solid storage.

(iii) The waste materials released by animals are decom­posed by bacteria and find their way in soluble inor­ganic form to soil storage. Thus, biogeochemical cy­cles involve the movement and circulation of soluble inorganic substances (nutrients) derived from sedi­mentary and atmospheric phases of inorganic sub­stances (the two basic components of inorganic phase) through biotic phase and finally their return to inor­ganic state.

The study of biogeochemical cycles may be approached on two scales:

(i) The cycling of all the elements together, or

(ii) Cycling of individual elements e.g., carbon cycle, oxygen cycle, nitrogen cycle, phos­phorous cycle, sulphur cycle etc.

Besides, hydrological cycle and mineral cycles are also included in the broader biogeochemical cycles.