Here is a compilation of essays on an ‘Ecosystem’ for class 8, 9, 10, 11 and 12. Find paragraphs, long and short essays on an ‘Ecosystem’ especially written for school and college students.
Essay on an Ecosystem
- Essay on the Definition of Ecosystem
- Essay on the Structure of an Ecosystem
- Essay on the Basic Requirements of an Ecosystem
- Essay on the Pond – An Example of Ecosystem
- Essay on the Kinds of Ecosystem
- Essay on the Decomposition in an Ecosystem
- Essay on the Examples of Ecosystem Services
Essay # 1. Definition of an Ecosystem:
Ecosystem (Gr. eco—environment; system = interacting and interdependent complex) is an integrated system resulting from interaction of living and non-living factors of the environment. In other words, the ecosystem can also be defined as any unit which includes all the organisms (i.e., communities) in a given area, interacts with the physical environment e.g. water, air, soil etc. by means of food chains and chemical cycles resulting in energy-flow, biotic diversity and material cycling. It is also called ecological system.
The ecosystems may be permanent and natural or temporary. Common examples of natural ecosystems are a pond, a lake, a desert, a meadow, a grassland or a forest. A balanced aquarium is also an example of ecosystem. Examples of temporary ecosystems are a protozoan culture medium, a rainfed pond, etc.
Essay # 2. Structure of an Ecosystem:
An ecosystem is composed of the abiotic physico- chemical environment and biotic assemblage of plants, animals and microbes. These components collectively form a natural, stable, self-sufficient and functional ecological unit, called ecosystem.
Odum (1971) described that an ecosystem is formed of two major components:
A. Biotic (living) components
B. Abiotic (non-living) components.
A. Biotic Components:
These include the living elements of the ecosystem and are divided into two categories on the basis of their nutritional relationship:
i. Autotrophic components.
ii. Heterotrophic components.
i. Autotrophic Components (Gr. fluto—self; trophos —feeder):
These include the green plants, photosynthetic bacteria and cyanobacteria which are capable of manufacturing their organic food (e.g. glucose) from simple inorganic substances (e.g. CO2 and H2O) by the process of photosynthesis. Chemosynthetic bacteria (which synthesize their organic food from inorganic materials in the presence of chemical energy) also act as producers though they fix only a very small amount of carbon dioxide.
These include iron bacteria and nitrifying bacteria. The energy trapped in photosynthesis is the radiant energy of sun and is changed into chemical energy. These are also called producers. These may be herbs, shrubs, large sized trees in a terrestrial ecosystem; or microscopic, free-floating phytoplanktons, algae or large sized green plants in an aquatic ecosystem. The glucose is used by the plants to synthesize the complex organic compounds like starch, proteins, lipids, etc.
Importance of Producers:
These form primary basis of life and provide food, shelter and oxygen to the animals. These also maintain CO2/O2balance of nature.
ii. Heterotrophic Components (Gr. heteros—other; trophos—feeder):
These include those organisms which consume either readymade organic food or decompose the complex organic compounds. These are also called consumers. These do not have chlorophyll, so cannot synthesize their own food.
Depending upon their size, heterotrophs are divided into two categories:
(a) Macro Consumers:
These include the animals, which eat or ingest the producers directly or indirectly. These are also called phagotrophs.
On the basis of nature of food, these are divided into four categories:
(i) Primary Consumers or Consumers of First Order:
These include the herbivores which directly eat upon the plants e.g. insects, birds, rabbit, deer, goat, cattle, grasshoppers etc. in a terrestrial ecosystem. Herbivores of aquatic ecosystem include crustaceans, molluscs and protozoans.
(ii) Secondary Consumers or Consumers of Second Order:
These include the primary carnivores which eat upon the herbivorous animals e.g. fox, frog, centipede, predatory birds, fishes, wild cats, snakes etc.
(iii) Tertiary Consumers or Consumers of Third Order:
These include the secondary carnivores which eat upon the secondary consumers (or primary carnivores) e.g. wolf eating upon the fox.
(iv) Quaternary Consumers or Consumers of Fourth Order:
These include the tertiary or top carnivores which eat upon the tertiary consumers (or secondary carnivores) e.g. lion, tiger etc. These are not eaten by other animals.
(b) Micro Consumers:
These are also called decomposers or saprotrophs (Gr. sapros—rotten; trophos = feeder) or reducers which break down the complex organic compounds of dead bodies of both plants and animals, absorb some of the decomposed products while release most of inorganic compounds into the environment from where these are reused by the producers.
So these help in material cycling. These secrete digestive enzymes to digest the organic compounds externally. These include the non-green microscopic organisms like bacteria and fungi (e.g. moulds, mushrooms, etc.).
The producers, phagotrophs and saprotrophs are biotic components of ecosystem and are usually considered as three functional kingdoms of nature.
B. Abiotic Components:
These include the non-living physico-chemical factors of environment. These affect the distribution, structure, behaviour and interrelationship of organisms.
These are divided into the following three categories:
1. Inorganic Materials:
These are involved in the material cycles e.g. Carbon, Nitrogen, Phosphorus, CO2, H2O, etc.
2. Organic Compounds:
These are present in dead organic matter and include carbohydrates, proteins, lipids, humic substances, nucleic acids, etc. These provide a link between living and non-living factors.
3. Climatic and Edaphic Factors:
Climatic factors include physical factors of environment which include light, temperature, humidity wind, etc. The edaphic factors are associated soil factors which include pH, topography, etc. of soil.
Essay # 3. Basic Requirements of an Ecosystem:
Though most of ecosystems have macro consumers or animals as their integral part but basic requirements of self-sustaining ecosystem are:
1. Inorganic nutrients (e.g. CO2 and H2O).
2. Autotrophs or producers (e.g. plants).
3. Micro consumers or decomposers (e.g. bacteria and fungi).
4. A source of continuous supply of energy (e.g. sun).
Biotic communities are generally vertically arranged or stratified. The term stratification refers to the arrangement of different animals and plants in different layers of the substratum. If increases the number of habitats so reduces the interspecific competition. A number of examples can be cited to support the concept of community stratification from different habitats.
(a) Grassland Community:
Three strata, namely subterranean, floor and herbaceous strata can be recognized.
(i) Subterranean Stratum:
It is represented by the organisms embedded in the soil e.g. bacteria, fungi, protozoans, spiders, nematodes, earthworms and other invertebrates.
(ii) Floor Stratum:
It is represented by basal portions of the vegetation including runners, suckers and rhizomes of grass family. Among the animals, insects, spiders, lizards, snakes and rodents are present.
(iii) Herbaceous Stratum:
It is represented by herbs, insects, birds and grazing animals.
(b) Forest Community:
Stratification of land communities reaches the greatest complexity in the forest community. Typically, in a forest, five vertical strata are present.
(i) Overstory stratum represented by trees more than 40 feet in height. These trees form a canopy.
(ii) Understory stratum represented by trees 20-40 feet in height.
(iii) Transgressive stratum represented by plants 4-20 feet in height. It is comprised by shade loving species.
(iv) Seedling Stratum:
It begins at the soil level and extends to the lower limit of transgressive stratum. It is the stratum of great biological activity.
(v) Subterranean Stratum:
It is typically damp and contains large amount of humus. It extends from surface up to depth of 2-3 metres. It is occupied by burrowing animals and bacterial types.
Each stratum has its own group of animals. But for animals the stratification is not so rigid because of their mobility. Often animals move from one stratum to another in search of food or in response to numerous abiotic factors.
(c) Pond or Lake Community:
In ponds, vertical stratification is very little.
However, in deep ponds and lakes, three zones or strata can be recognized:
(i) Littoral zone represented by shallow water having rotten plants. It includes rooted plants.
(ii) Limnetic zone occupies depth up to which light penetrates in water and has planktons, nektons and neustons.
(iii) Profundal zone represented by the area where sunlight cannot penetrate. This zone lacks photosynthetic organisms. The mud contains only anaerobic bacteria, fungi and other micro-organisms.
Stratification increases the number of habitats which reduces the interspecific competition.
Essay # 4. Pond – An Example of Ecosystem:
A small fresh-water pond is a classic example of an ecosystem to explain its structure and function (Fig. 14.5).
Pond represents a self-regulatory and self- sustainable freshwater ecosystem. The salient features of a pond are abundant vegetation, innumerous microorganisms, large number of plants and animals present in relatively quiet, shallow and standing water.
Essay # 5. Kinds of Ecosystem:
Arbitrarily, the various ecosystems in the world can be grouped under two kinds:
1. Natural Ecosystem:
These types of ecosystem operates under natural conditions without much interference of man and can be further divided into the following kinds:
(i) Terrestrial ecosystem:
It comprises of grassland, forest, desert and so on.
(ii) Aquatic ecosystem:
It can be further subdivided into —
(a) Fresh water:
Fresh water comprising of lentic (standing water system such as ponds, lakes, pools, ditches etc.) or lotic (running water system such as rivers, streams, springs etc.) water conditions.
(b) Salt water:
Salt water comprising of sea, deep sea, estuaries, salt water bheries, and salt water lakes etc.
(iii) Wetland ecosystem:
It comprises of marsh, bog, fen, shrubcarr and swamp.
2. Artificial Ecosystem:
Here the natural balance of nature is frequently disturbed by manipulation and addition of energy.
Intensive culture of prawns in an impoundment, artificially maintained pond, croplands like maize, wheat, rice-fields etc.
The study of an ecosystem:
Large, complex ecosystems can be approached in two ways:
1. Holological (holos, whole):
Here the inputs and outputs are measured collectively. The properties that emerges of the whole ecosystem are assessed and then the component parts are investigated as needed.
2. Merological (meros, part):
Here the major components of the ecosystems are studied first and then integrated into a whole system.
Essay # 6. Decomposition in an Ecosystem:
Decomposition is the process by which complex organic compounds are broken into simpler and inorganic substances that can be reutilized by the plants for their growth. It also provides energy and nutrients to the decomposers which include bacteria and fungi.
Rate of Decomposition:
Different organic compounds are decomposed at different rates e.g. compounds like carbohydrates, fats and proteins are decomposed rapidly, while compounds like cellulose, lignin, chitin, hair and bones are decomposed very slowly.
Mechanism of Decomposition:
Decomposition is a complex process of enzymatic reaction and involves the step-wise degradation of detritus (dead organic matter formed of excreta of animals and dead bodies of plants and animals). Detritus acts as raw material for decomposition.
It involves following processes:
i. Fragmentation of detritus by detritivorous organisms like many types of bacteria and fungi, and invertebrates like earthworms. This increases the surface area of detritus particles for the microbial action. These detritivores also add certain growth substances which stimulate the microbial growth.
Some of these detritivores are coprophagic (kopros = dung) and cause breakdown of faecal pellets of animals. It is estimated that one gram of soil may contain one billion bacteria, 5 million members of Actinomycetes, 500,000 protozoans and 200,000 moulds of different types.
It is process by which simple and water soluble compounds like simple sugars and inorganic nutrients move downward along with percolating gravitational water. These inorganic nutrients are precipitated to form non-available salts.
In this, decomposers release extracellular enzyme in their surroundings to breakdown detritus into simple organic compounds and inorganic substances. Specific decomposers perform specific chemical actions on specific complex compounds through specific enzymes e.g. Pseudomonas bacteria decompose the proteins into ammonia and simple nitrogen compounds.
It is process by which simplified detritus is changed into dark coloured amorphous substance called humus. It is highly resistant to microbial action so undergoes decomposition at an extremely slow rate. Humus acts as a reservoir of nutrients.
It involves the release of inorganic substances (e.g. water, CO2, etc.) and other nutrients (NH4+, Ca++, Mg++, K+ etc.) in the soil.
Factors Affecting Decomposition:
Decomposition is affected by two categories of factors:
A. Climatic Factors e.g:
It is most important factor affecting the decomposition rate e.g. in tropical areas with high temperature (> 25°C) and moist conditions, the detritus decomposes very rapidly. Conversely, decomposition rate is very low in regions of high altitude or latitude characterized by low temperature (< 10°C) though has sufficient soil moisture. In these area, decomposition is completed in several years.
(ii) Soil Moisture:
Rate of decomposition is low in soil with low moisture e.g. in tropical deserts, there is low decomposition rate even in high temperature. It is so because these have low soil moisture.
Decomposition is largely an oxygen- requiring process so anaerobiosis inhibits the rate of decomposition which causes accumulation of organic substances.
B. Chemical Quality of Detritus:
It is determined by relative proportions of water-soluble substances like sugars, polyphenols, lignin and nitrogen. Presence of lignin and chitin decrease the decomposition rate while the presence of nitrogen-containing and water- soluble substances increase the rate of decomposition.
Essay # 7. Examples of Ecosystem Services:
i. Services (Benefits) of a Healthy Forest Ecosystem:
(i) The forests provide food in the form of roots, tubers, leaves and fruits especially for the tribals.
(ii) The forests provide fuel in the form of wood for cooking and keeping warm. Over 1000 million tonnes (more than 80% of total fuel) of wood is used as fuel in the world.
(iii) Forests provide timber for building purposes of houses, ships, railway sleepers, sport goods, agricultural tools, toys, etc.
(iv) Forests also provide a number of useful products like camphor, essential oils, tannins, dyes, gums, resins, soap substitutes, drugs, etc.
(v) These keep the environment cool by regulating transpiration and precipitation.
(vi) Plants produce oxygen during photosynthesis for respiration of animals.
(vii) These provide shelters to a variety of animals and plants (e.g. mosses, ferns etc.)
(viii) These prevent soil erosion by binding the soil particles and regulating the floods and wind velocity so help in conservation of soil.
(ix) These also have aesthetic, cultural and spiritual importance.
ii. Services Provided by Watersheds:
A watershed is an area of high land from which water flows under gravity into river or sea. It has a well defined topographic boundary with only one outlet of wafer. The watersheds supply water for irrigation, hydropower generation, transportation, vegetation growth and reducing the chances of floods and droughts. So watersheds improve the economy of the region.
Other sources of ecosystem services are wetlands, wild life, mineral resources, energy services, etc.
Price Tag on Ecosystem Services:
Robert Constanza et.al. have recently put price tags on nature’s life- supporting services. It is proposed an average price tag of US$ 33 trillion a year on these fundamental ecosystem services which is nearly three times the value of the global gross national product (GNP).
Out of the total price tag on various ecosystem services, the soil formation accounts for about 50%; recreation services for about 10%; nutrient cycling for about 10%; 6% for climatic regulation; 6% for wild life management; etc.
But as these ecosystem services are free so these are taken for granted and most of societies believe in anthropogenic world view which states that success and healthy economy of mankind depend upon how nicely man derives benefits from nature.
So the human beings are over-exploiting the natural resources and polluting the environment. It is being further compounded by population explosion. These human acts are very dangerous and may lead to environmental crisis which may threaten even the existence of mankind.
So there is an urgent need of developing the essence of environmental ethics and Eco-centric worldview m the human beings. This view states that the natural resources are limited and the success and healthy economy of mankind depend upon the healthy environment.
The environmental ethics include the human obligations towards the environment and demand that man should learn to live as a part of nature and not as a master of nature. They must make sincere efforts to renew the natural resources so that sustainable development is achieved.