Eco System (Environmental science)

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ECOSYSTEM

INTRODUCTION:

An ecosystem is a biological environment consisting of all the organisms

living in a particular area, as well as all the non-living, physical components of the

environment with which the organisms interact, such as air, soil, water and

sunlight. It is all the organisms in a given area, along with the non-living (abiotic)

factors with which they interact: a biological community and its physical

environment. The entire array of organisms inhabiting a particular ecosystem is

called community. In a typical ecosystem, plants and other photosynthetic

organisms are the producers that provide the food. Ecosystem can be permanent

or temporary.

MEANING AND DEFINITION OF ECOSYSTEM:

The term Ecosystem is derived from the words eco and system. The

term eco refers to environment and system means a complex coordinated

unit (i.e., an interacting and inter-dependent complex). Ecosystem means a

system of organisms interacting with their environment. In other words,

ecosystems are functional units consisting of living things in a given area, non-

living chemical and physical factors of their environment, linked together throughnutrient and energy flow.

Central to the ecosystem concept is the idea that living organisms interact

with every other element in their local environment. EUGENE ODUM, a founder

of ecology, stated: Andy 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 cycles (i.e., exchange of materials between living and non living parts)within the system is an ecosystem.

A.G. Tansley defined the ecosystem as the system resulting from the

integration of all the living and non-living factors of the environment.


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CONCEPT OF ECOSYSTEM - CHARACTERISTICS:

The term ecology was coined by Earnst Haeckel in 1869. It is derived fromthe Greek words OKIOS (meaning HOUSE) and LOGOS (meaning

STUDY). So ecology deals with the study of organisms in their naturalhome interacting with their surroundings.

An ecosystem is a group of biotic communities of species interacting withone another and with their non-living environment exchanging energy and

matter.

Now ecology is often defined as The study of ecosystem.The ecosystem is a unit or a system, which is composed of a number of

subunits that are all directly or indirectly linked with each other.

They may be freely exchanging energy and matter from outside-an openecosystem or may be isolated from outside-a closed ecosystem.

STRUCTURE OF AN ECOSYSTEM:

The structure of an ecosystem is the relationship between the abiotic (non-

living) and the biotic (living) components.

BIOTIC STRUCTURE: The plants, animals and microorganisms present in anecosystem form the biotic component. These organisms have different

nutritional behaviour and status in the ecosystems and are accordingly

known as PRODUCERS or CONSUMERS, based on how they get their

food.

ABIOTIC STRUCTURE: The physical and chemical components of anecosystem constitute its abiotic structure. It includes climatic factors,

edaphic (soil) factors, geographical factors, energy, nutrients and toxic

substances.

COMPONENTS OF ECOSYSTEM - STRUCTURE:

Ecosystem is a defined area in which a community lives with interaction

taking place among the organisms between the community and its non-living


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physical environment. An ecosystem is formed by the interaction between all

living and non-living things.

BIOTIC COMPONENTS:The biotic components can be classified into three components according

to their mode of energy acquisition. They are explained as below:

AUTOTROPHY-PRODUCERS:Organisms that produce their own food from an energy source, such as the

sun and inorganic compounds are known as producers. Producers are able to

capture the suns energy through photosynthesis and absorb nutrients from the

soil, storing them for future use by themselves and by other organisms such asgrasses, shrubs, trees, mosses, lichens and cyanobacteria.

Producers are mainly the green plants, which can synthesize their food

themselves by making use of carbon dioxide present in the air and water in the

presence of sunlight by involving chlorophyll, the green pigment present in the

leaves, through the process of photosynthesis.

They are also known as photo autotrophs (auto=self; troph=food; photo=light).

There are some microorganisms also which can produce organic matter to someextent through oxidation of certain chemicals in the absence of sunlight. They are

known as chemosynthetic organisms or chemo-autotrophs. For instance in the

ocean depths, where there is no sunlight, chemoautotrophic sulphur bacteria

make use of the heat generated by the decay of radioactive elements present in

the earths core and released depths. They use this heat to convert dissolved

hydrogen sulphide (H2S) and carbon dioxide (CO2) into organic compounds. The

following equation explains it.

Energy

6CO2+6H2O 6C6H12O6 + 6O2

Sunlight


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HETEROTROPHS-CONSUMERS:Organisms that consume other organisms as a food source are called

consumers. Consumers are organisms that do not have the ability to capture the

energy produced by the sun, but consume plant and/or animal material to gaintheir energy for growth and activity. Consumers are further divided into four

types based on their ability to digest plant and animal material:

HERBIVORES: Herbivores eat only plants, such as the elk that graze thegrasslands of the Columbia valley, or an insect nibbling on the leaf of a

sticky geranium.

CARNIVORES: Carnivores eat only animals, such as the red-tailed hawk orwestern rattlesnake.

OMNIVORES: Omnivores eat both plants and animals, such as the blackbear, humans, rat, fox and many birds.

DETRIVORES (DETRIUS FEEDERS OR SAPROTROPHYS): They feed on theparts of dead organisms, wastes of living organisms, their castoffs and

partially decomposed matter e.g. beetles, termites, ants, crabs,

earthworms, etc.,

DECOMPOSERS :Decomposers include the insects, fungi, algae and bacteria both on the ground

and in the soil that help to break down the organic layer to provide nutrients for

growing plants. There are many millions of these organisms in each square metre

of grassland. Decomposers derive their nutrition by breaking down the complex

organic molecules to simpler organic compounds and ultimately into inorganic

nutrients.

Various bacteria and fungi are decomposers.In all the ecosystems, this biotic structure prevails.However, in some, it is the primary procedures, which predominate (e.g.

in forests, agro ecosystems) while in others the decomposers

predominate (e.g. deep ocean).


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ABIOTIC COMPONENTS: Physical factors- Solar energy provides practically all the energy for

ecosystems. Chemical factors- Inorganic substances, e.g., sulfur, boron, tend to cycle

through ecosystems.

Organic compounds- Such as proteins, carbohydrates, lipids and othercomplex molecules form a link between biotic and abiotic components of

the system.

The structure of an ecosystem can be represented as shown in Figure.

Classic Factors Edaphic Factors

Climatic Factors Procedures Decomposers

STRUCTURE OF AN ECOSYSTEM

FUNCTIONS 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 be understanding the history of

function studied. The function of an ecosystem can be discussed as shown below:

Tropic structure, food chain, food web and ecological pyramids.

ECOSYSTEM

ABIOTIC

Components

BIOTIC

Components


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The rate of biological energy flow i.e. production and respiration rates ofthe community.

Rate of materials or nutrient cycles.

Biological or ecological regulations, which include regulations on organismsby the environment (photoperiodism) and regulations on environment by

the organism (N2 fixation by organisms).

ECOSYSTEM PROCESS:

The major functional attributes of an ecosystem are as follows:

Energy flow through ecosystem.Trophic level interaction.Food chain.Food web.Ecological pyramids.Ecological succession.Productivity and decomposition.

Energy flow in an ecosystem:Energy is defines as the capacity to do work. For living organisms, it is the

basic force responsible for running all the metabolic activities. The flow of energy

from producer level to top consumer level is called energy flow. The flow of

energy in an ecosystem is unidirectional i.e. on way flow. It flows from producer

level to consumer level. The process of energy flow involves transfer of energy

from autotrophs to various components of heterotrophy and help in maintaining

bio-diversity. The main source of energy in the ecosystem is sunlight. About 80%

of energy is lost during flow of energy from one tropic level (A tropic level is the

position occupied by an organism in a food chain) to the next one. Energy

obtained is used for various body activities and to overcome entropy. Dissipation

energy occurs as heat.


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Trophic level interaction: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 throughthe ecosystem. Trophic level interaction deals with how the members of an

ecosystem are connected based on nutritional needs.

The trophic level interaction involves three concepts namely-

Food chain. Food web and

Ecological pyramids.

Trophic level interaction

Food chain:The sequence of eating and being eaten in an ecosystem is known as food

chain. All organisms, living or dead are potential food for some other organisms

and thus, there is essentially no waste in the functioning of a natural ecosystem.

A caterpillar eats a plant leaf, a sparrow eats the caterpillar, a cat or a hawk eats

the sparrow and when they all die, they are all consumed by microorganism like

bacteria or fungi (decomposers), which breaks down the organic matter and

convert it into simple inorganic substances that can again be used by the plants

the primary producers.


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Some examples of food chain are:

Grass Grasshopper Frog Snake Hawk (GRASSLANDECOSYSTEM).

Lichens Reindeer Man (MAN TUNDRA).

IMPORTANCE OF FOOD CHAIN:

The food chain studies help to understand the feeding relationships and

the interaction between organisms in an 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 ecosystem and the problem

of biological magnification.

Food web:It is a network of food chains where different types of organisms are

connected at different trophic levels, so that there are a number of options of

eating and being eaten at each trophic level.

In nature simple food chains occur rarely. The same organism may operate in

the ecosystem at more than one tropic level i.e. it may derive its food from more

than one source. Even the same organism may be eaten by several organisms of

a higher trophic level or an organism may feed upon several different organism 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 chain

are linked together and intersected each other to form a complex network called

food web.


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Food web

ADVANTAGES OF FOOD WEB:

They have rich species diversity and therefore, the food webs are much more

complex. The various advantages, which the food web possesses, are given

below:

Food webs give greater stability to the ecosystem.In a linear food chain, if one species becomes extinct or one species suffers

them the species in the subsequent trophic levels are also affected. In a

food web, on the other hand, there are a number of options available at

each trophic level.


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SIGNIFICANCE OF FOOD WEB:

The significance of food web can be understood from the following points

to its credit:

Food webs play a very significant role in the ecosystem because it its one ofthe most important functions of energy flow and nutrient cycling takes

place through it.

It helps maintain the ecological balance.

Ecological pyramids:Graphic representation of trophic structure and function of an ecosystem,

starting with producers at the base and successive trophic levels forming the apex

is known as an ecological pyramid.

In the successive steps of grazing food chain-photosynthetic autotroph,

herbivorous heterotrophy, carnivores and decay bacteria 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 pyramid represents the trophic structure

and also trophic function of the ecosystem.

TYPES OF ECOLOGICAL PYRAMID:

It is of three types namely,

Pyramid of numbers,Pyramid of biomass, andPyramid of energy.


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PYRAMID OF NUMBERS:It represents the number of individual organisms at each trophic level. We

may have upright or inverted pyramid of numbers, depending upon the type of

ecosystem and food chain.

Grassland ecosystem i.e. pyramid of number

A grassland ecosystem and a pond ecosystem show an upright pyramid of

numbers. The producers in the grasslands are grasses and that in a pond are

phytoplankton (algae etc.), which are small in size and very large in number. So

the producers form a broad base. The herbivores in grassland are rabbits while

tertiary carnivores are frogs which are gradually less and top carnivores like lion

and tiger are very less in number and hence the pyramid apex becomes gradually

narrower forming an upright pyramid.


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PYRAMID OF BIOMASS:Biomass is the amount of living matter in particular trophic level at any given

time. It is based upon the total biomass can also be upright or inverted. The

pond ecosystem shows an inverted pyramid of biomass. The total biomass ofproducers (phytoplanktons) is much less as compared to herbivores

(zooplanktons, insects), carnivores (Small fish), tertiary carnivores (big fish) and

decomposers (Bacteria). Thus the pyramid takes an inverted shape an inverted

shape with narrow base and broad apex.

Pyramid of biomass


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PYRAMID OF ENERGY:The amount of energy present at each trophic level is considered for this type

of pyramid of energy. There is a sharp decline in energy level of each successivetrophic level as we move from producers to top carnivores. Therefore, the

pyramid of energy is always upright. It gives the best representation of the

trophic relationships and it is always upright.

Pyramid of energy in grassland


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Ecological succession:In a particular area, one community of species may be replaced by another

community: the progressive replacement of one community of one community by

another till the development of stable community in a particular area is called asecological succession.

It is also defined in following three parameters:

It is an orderly process of the community changes or developments thatinvolve changes in species structure and community processes with time

and these changes are directional and predictable.

It results from the modification of physical environment and populationstructure by the community.

It reaches the highest point of establishment as stable an ecosystem as ispossible biologically on that particular site.

TYPES OF SUCCESSION:

Succession is of three types. They are-

Primary succession,Secondary succession, andAutogenic succession.

They are detailed here in below.

PRIMARY SUCCESSION:Primary succession is an initial development of an ecosystem. If an area in

any of the basic environments (such as terrestrial, fresh-water or marine) is

colonized by organisms for the first time, the succession is called primary

succession.

SECONDARY SUCCESSION:Secondary succession refers to re-establishment of an ecosystem. It occurs

when an existing community is disrupted and a new one subsequently


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developed at the site. In other words, if the area under colonization has

been cleared by whatsoever agency (such as burning, grazing, clearing,

falling of trees, sudden change in climate factors, etc.) of the previous

plants, it is called secondary succession.

AUTOGENIC SUCCESSION:After the succession has begun, in most of the cases, it is the community

itself (as a result of its reactions with the environment) modifies its own

environment and, thus, causing its own replacement by new communities.

This course of succession is known as autogenic succession.

CAUSES OF ECOLOGICAL SUCCESSION:

Various causes of ecological succession can be grouped under three headsas shown below:

Initial causes: Climate (wind, fire, soil erosion and deposits). Biotic (activities of the organisms)

Ecesis causes/ Continuous causes: Migration. Aggregation. Competition. Reaction.

Stabilization causes: Climate.

PROCESS OF SUCCESSION:

The process of succession takes place in a systematic order of sequential stepsas follows:

NUDATION: It is the development of a bare area, without any life form.The bare area may be caused due to several anthropogenic activities.


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INVASION: It is the successful establishment of one or more species on abare area through dispersal or migration, followed by ecesis or

establishment.

COMPETITION AND COACTION: as the number of individuals grows, there iscompetition for space, water and nutrition. They influence each other in a

number of ways, known as coaction.

REACTION: The living organisms have a strong influence on theenvironment, which is modified to a large extent and this is known as

reaction.

STABLIZATION (CLIMAX): the succession ultimately culminates in a more orless stable community called climax, which is in equilibrium with the

environment.

Let us consider very briefly two types of succession.

HYDROSERE (HYDRARCH): This type of succession starts in a water bodylike pond. A number of intermediate stages come and ultimately it

culminates in a climax community, which is a forest.

XEROSERE (XERARCH): This type of succession originates on a bare rock,which lack water and organic matter. Interestingly, here also the climax

community is a forest, although the intermediate stages are very

different.

Productivity and decomposition:PRODUCTIVITY:

The rate of production of organic matter or biomass is called productivity. Its

of two types:

PRIMARY PRODUCTIVITY: The rate at which solar energy is observed byplants (producers) for synthesis of organic compounds through

photosynthesis is called primary productivity. Primary productivity is

further divided into two types. They are-


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Gross Primary Productivity (GPP): Rate of total production oforganic matter/ biomass by the producers per unit area and time.

Net Primary Productivity (NPP): Rate at which the energy or organicmatter spared by the producers after respiration and maintenance

per unit area.

NPP = GPP LOSS DUE TO RESPIRATION AND MAINTENANCE

SECONDARY PRODUCTIVITY: Rate of increase in biomass of consumersper unit area and time.

DECOMPOSTION:Decomposition refers to the process by which complex organic materials are

broker into inorganic like carbon dioxide, ware and nutrients by decomposers.

TYPES OF ECOSYSTEM:

In a marvelous way all the living, non-living and climate conditions of a

place are interconnected and a geographical area along with this interconnected

network is termed as an ECOSYSTEM. Ecosystems differ in flora, fauna and

weather but all of them support some kind of life. Therefore, it is very important

to understand the features of the ecosystem before entering it and trying to makechanges. It was lack of this understanding in early days that led to exploitation of

the natural habitats and extinction of many rare species along with destruction of

some beautiful landscapes. There are many important energy and matter

transformation cycles that run through these ecosystems. Human beings are

known to act in manners, which disrupt these cycles and disrupt the natural flow

of things in an ecosystem. This leads to major problems in the ecosystems as links

of cycles get detached and stability of the system is lost. To prevent this from

happening we need to understand what type of ecosystem we are dealing with.This is just a brief introduction to a subject, which requires in depth study.

CLASSIFICATION OF ECOSYSTEM:

We shall now discuss the various types of ecosystem in detail herein below.

Ecosystems are of two types. They are as follows:


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Natural ecosystem.Artificial ecosystem.We shall now detail each one of them as shown below:

NATURAL ECOSYSTEMS:These operate by themselves under natural conditions without any major

interference by man. Based upon the particular kind of habitat, these are further

divided as:

Terrestrial Ecosystem Terrestrial ecosystem is one which encompassesthe activities that takes place on land. E.g. forest, grassland, desert and

mountain ecosystem.

Aquatic Ecosystem exists in water bodies. It is further distinguished as: Freshwater ecosystem, which may be lotic (spring, stream or river) or

lentic (lake, pond, pools, ditch, swamp, etc.,)

Marine ecosystem, e.g. sea or ocean (deep bodies) and estuary(shallow bodies).

We shall now discuss the various types of natural ecosystem in detail here

in below.

TERRESTRIAL ECOSYSTEM:THE FOREST ECOSYSTEM:

These are the ecosystems where abundance of flora (plants) is seen

and they have a large number of organisms living in relatively small areas.

Therefore, the density of life in forest ecosystems is very high. Any small

change in the ecosystem can affect the whole balance and collapse the

ecosystem. You can see wonderful diversity in the fauna of these

ecosystems too. They are again divided into few types.

TROPICAL EVERGREEN FOREST: Tropical forests are those, which receivean average rainfall of 80 to 400 inches in a year. These forests are


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marked by dense vegetation comprising of tall trees with different

levels. Each level gives shelter to different kinds of animals.

TROPICAL DECIDUOUS FOREST: Dense bushes and shrubs rule herealong with broad levels of trees. This type of forests is found in many

parts of the world and large variety of flora and fauna are found here.

TEMPERATE EVERGREEN FOREST: It has very few number of trees butferns and mosses make up for them. Trees have spiked leaves to

minimize transpiration.

TEMPERATE DECIDUOUS FOREST: This forest is found in the moisttemperate regions with sufficient rainfall. Winters and summers are

well defined and with trees shedding their leaves during winter.

TROPICAL SCRUB FOREST: It is found in areas where the day season iseven.

TAIGA: Situated just south of the arctic regions, taiga. Is distinguishedby evergreen confers. While the temperature is subzero for almost six

months, the rest of the year it is buzzing with insects and migratory

birds.

EVERGREEN CONIFEROUS FOREST (BOREAL FORESTS): They are foundjust south of arctic tundra. Here winters are long, cold and dry. Sunlight

is available for a few hours only.

ABIOTIC COMPONENTS IN THE FOREST ECOSYSTEM:

The abiotic environment of forest ecosystem includes the nutrients present

in the soil in forest floor, which is usually rich in dead and decaying organic

matter.

BIOTIC COMPONENTS IN THE FOREST ECOSYSTEM:

The biotic components in the forest ecosystem are as below:

PRODUCERS: Producers are mainly big trees, some shrubs andground vegetation.


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PRIMARY CONSUMERS: Primary consumers are insects like ants,flies, beetles, spiders and big animals like elephants, deer, squirrels,

etc.

SECONDARY CONSUMERS: Secondary consumers are carnivores likesnakes, lizards, foxes, birds, etc.

TERTIARY CONSUMERS: Tertiary consumers are animals like tiger,lion, etc.

DECOMPOSERS: Decomposers are bacteria, fungi, which are found insoil on the forest floor. Rate of decomposition in tropical or sub-

tropical forests is more rapid that that in the temperate zones.

THE DESERT ECOSYSTEM:Desert ecosystems are found in regions receiving an annual rainfall of less

than 25cm. They occupy around 17 percent of all land on the planet. Due to very

high temperature, intense sunlight and low water availability, flora and fauna are

very poorly developed and scarce. Vegetation is mainly bushes, shrubs, few

grasses and rarely trees. Leaves and stems of these plants are modified to

conserve water. The best known desert plants are the succulents like spiny

leaved cacti. Animal life includes insects, reptiles, birds, camels all of whom are

adapted to the xeric (desert) conditions.

Deserts are of three major types, based o climate conditions:

TROPICAL DESERTS: Tropical deserts like Sahara in Africa and TharDesert, Rajasthan, India are the driest of all with only a few species.

TEMPERATURE DESERTS: Temperature deserts like Mojave in SouthernCalifornia where day time temperatures are very hot in summer but cool

in winters.

COLD DESERTS: Gobi desert in China have cold winters and warmsummers.


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BIOTIC COMPONENTS IN THE DESERT ECOSYSTEM:

The biotic components of desert ecosystem are as below:

PRODUCERS: The chief producers are shrubs, bushes and some treeswhose roots are very extensive and stems and leaves are modified to

store water and to reduce loss of water as a result of transpiration. Low

plants such as mosses and blue green algae are minor producers.

PRIMARY CONSUMERS: Primary consumers are animals like rabbits,which get water from succulent plants. They do not drink water even if

it is freely available. Camel is also a primary consumer of the desert.

SECONDAY CONSUMERS: Secondary consumers are carnivores likereptiles having impervious skin, which minimize loss water from thesurface of body.

TERTIARY CONSUMERS: The tertiary consumers are mainly birds, whichconserve water by excreting solid uric acid.

DECOMPOSERS: Decomposers are bacteria and fungi, which can thrivein hot climate conditions. Because of scarcity of flora and fauna, the

dead organic matter available is much less and therefore decomposers

are also less in number.

An example of food chain commonly found in desert ecosystem is given below:

Shrub Rabbits Reptiles Birds

THE GRASSLAND ECOSYSTEM:Grasslands are regions with enough average annual rain precipitation to

allow grass to grow extensively. But drought and fire do not allow trees to grow

taller. Grasslands are rich biological communities of grasses, seasonal floweringplants and open savannas. Great Plains of central North America, Russia and

South America are some of the important grasslands in the world. Grasslands are

found in both temperate and tropical regions of the world but the ecosystem are

slightly varying. This area mainly comprises of grasses with very little amount of

shrubs and trees. Main vegetation is grasses, legumes and plants belonging to


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composite family. Many grazing animals, herbivores and insectivores are found in

grasslands. The main types of grasslands ecosystems are:

Tropical grasslands Temperate grasslands Polar grasslands

TROPICAL GRASSLANDS:Tropical grasslands has warm temperature year around with two prolonged

dry seasons. They are the shelter for animals like zebras, giraffes, black rhino and

African elephant. Savanna grassland in Africa is good example for tropical

grassland.

TEMPERATE GRASSLANDS:In temperate grasslands, winters are too cold, summers are hot and dry,

annual precipitation is less and falls unevenly through the year. Drought, fire and

overgrazing inhibit the growth of trees and bushes in these grasslands. The soil in

temperate grassland is fertile since grass die and decomposes to organic manure.

Prairies in Canada, Pampas in South America and Veldt in Africa are examples for

temperate grasslands.

POLAR GRASSLANDS:Polar grassland is also known as ARCTIC TUNDRA. They occur in arctic polar

icecaps. The land is covered with ice and snow. Winter is very dark, long and

cold. Seasonal cycles of temperature and precipitation contributes to abundant

vegetative growth that enriches and protects the soil of the grasslands. There is

enough water to support small crops to do photosynthesis. Grasslands have few

trees because inadequate rainfall, large daily and seasonal temperature rangesand frequently grass fires kill woody seedlings.

MAJOR IMPACTS ON GRASSLANDS: Major impacts on grassland ecosystem are

as follows:

Conversion of grasslands into cropland.


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Overgrazing of grasslands by livestock. Exploitation of polar grasslands by oil, water and air pollution.

BIOTIC COMPONENTS IN THE GRASSLAND ECOSYSTEM: The biotic components

in the grassland ecosystem are as below:

PRODUCERS: Producers are mainly grass and some herbs, shrubs andfew scattered trees.

PRIMARY CONSUMERS: Primary consumers are grazing animals suchas cow, sheep, deer, house, kangaroo, etc. Some insects and spiders

have also been included as primary consumers.

SECONDARY CONSUMERS: Secondary consumers are animals like fox,jackals, snakes, lizards, frogs, birds, etc.,

THE MOUNTAIN ECOSYSTEM:Mountain lands provide a scattered but diverse array of habitats in which a

large range of plants and animals are found. At higher altitudes harsh

environmental conditions generally prevail and only treeless alpine vegetation is

found. The animals living here have thick fur coats for prevention from cold and

hibernate in winter months. Lower sloped commonly are covered by coniferous

forests.

AQUATIC ECOSYSTEMS:An aquatic ecosystem is an ecosystem located in a body of water. It

comprises aquatic fauna, flora and the properties of water too. There are two

types of aquatic ecosystems namely, Marine and Freshwater.

THE MARINE ECOSYSTEM:Marine ecosystems are the largest ecosystems with coverage of nearly 71%

of the earths surface and containing 97% of the planets water. The water in

marine ecosystems has salts and minerals dissolved in them in high amounts.

DIFFERENT DIVISIONS OF MARINE ECOSYSTEM: Different divisions of marine

ecosystem are given below:


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Oceans:These are gigantic reservoirs of water covering more than 70% of our

earths surface and play a key role in the survival of about 2,50,000 marine

species, serving as food for humans and other organisms, give a huge variety ofsea products and drugs. Oceans provide us iron, phosphorus, magnesium, oil

natural gas, sand and gravel. Oceans are the major sinks of carbon dioxide and

play an important role in regulating many biogeochemical cycles and hydrological

cycle, thereby regulating the earths climate.

TYPES OF LIFE ZONES IN OCEANS:

COASTAL ZONE: It is relatively warm, nutrient rich shallow water. Dueto high nutrients and ample sunlight this is the zone of high primary

productivity.

OPEN SEA ZONE: It is the deeper part of the ocean, away from thecontinental shelf. It is vertically divided into three regions:

EUPHOTIC ZONE: Euphotic zone is one, which receives abundant lightand shows high photosynthetic activity.

BATHYAL ZONE: It receives dim light and is usually geologicallyactive.

ABYSSAL ZONE: It is the dark zone, 2,000 to 5,000 meters deep. Theabyssal zone has no primary source of energy i.e. solar energy. It is

the worlds largest ecological unit but it is an incomplete ecosystem.

ESTUARIES:Estuary is a partially enclosed coastal area at the mouth of a river where

fresh water and salty seawater meet. There are the transition zones, which are

strongly affected by tidal action. Constant mixing of water stirs up organismspresent in estuaries show a wide range of tolerance to temperature and salinity.

Such organisms are known as eurythermal and euryhaline. Coastal and many of

the species are endemic. There are many migratory species of fishes like eels and

salmons in which half of the life is spent in freshwater and half in salty water. For

them estuaries are ideal places for resting during migration, where they also get


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abundant food. Estuaries are highly productive ecosystems. The river flow and

tidal action provide energy for estuary thereby enhancing its productivity.

Estuaries are of much use to human beings due to their high food potential.

However, these ecosystems need to be managed judiciously and protected from-

salt marshes, coral reefs and hydrothermal vents- where chemosynthetic bacteria

form the food base.

Many types of organisms are found in marine ecosystems including brown

algae, dinoflagellates, corals, cephalopods, echinoderms and sharks.

THE FRESHWATER ECOSYSTEM:In contrast to the marine ecosystem freshwater ecosystem only cover 0.8%

of the earths surface and contain 0.009% of its total water. There are three basic

types of freshwater ecosystems:

LENTIC: Still or slow-moving water like pools, ponds and lakes. LOTIC: Fast-moving water like streams and rivers. WETLANDS: Places where the soil is saturated or inundated for at

least some time.

These ecosystems are home to amphibians, reptiles and almost 41% of worlds

fish species. Faster moving turbulent water typically contains greater

concentration of dissolved oxygen, which supports greater bio-diversity than the

slow moving water of pools.

POND ECOSYSTEM:Pond ecosystem is a small freshwater aquatic ecosystem where water is

stagnant. Ponds may be seasonal in nature i.e. receiving enough water during

rainy season. Ponds are usually shallow water bodies, which play a veryimportant role in the villages where most of the activities centre around ponds.

They contain several types of algae, aquatic plants, insects, fishes and birds. The

ponds are however, very often exposed to tremendous anthropogenic pressures.

They are used for washing clothes bathing, swimming, cattle bathing and drinking,

etc. and therefore get polluted.


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POND ECOSYTEM

An example of natural ecosystem can be explained with the help of the

freshwater pond ecosystem. The abiotic factors include water, CO2, O2, organic

and inorganic compounds, light, temperature and pressure. The rooted plants

and submerged plants are the examples for producers in a pond ecosystem. The

consumers include insect larvae and snails. Bacteria are the decomposers, which

are otherwise called reducers.


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LAKE ECOSYSTEMS:Lakes are usually big freshwater bodies with standing water. They have

shallow water zone called littoral zone, an open-water zone called limnetic

zone and deep bottom area where light penetration is negligible, known asprofundal zone.

ORGANISMS FOUND IN LAKES: Lakes have several types of organisms:

PLANKTONS: Planktons float on the surface of waters e.g. phytoplanktonlike algae and zooplanktons like rotifers.

NEKTONS: Nektons swim e.g. fishes. NEUSTONS: Neustons rest or swim on the surface. BENTHOS: Benthos are attached to bottom sediments e.g. snails. PERIPHYTONS: Periphytons are attached or clinging to other plants or

any other surface e.g. crustaceans.

STRATIFICATION IN LAKES:

The lakes show stratification or zonation based on temperature differences.

During summer, the top waters become warmer than the bottom waters.

Therefore, only the warm top layer circulates without mixing with the colderlayer, thus forming a distinct zonation:

EPYILIMNION: Warm, lighter, circulating surface layer.

HYPOLOMNION: Cold, viscous, non-circulating bottom layer.

TYPES OF LAKES: The types of lakes are detailed as shown below:

OLIGOTROPIC LAKES: Oilgotrophic lakes are those, which have lownutrient concentrations.

EUTROPHIC LAKES: Eutrophic lakes are those, which are overnourished by nutrients like nitrogen and phosphorus, usually as a

result of agricultural run-off or municipal sewage discharge. They are

covered with Algae Blooms e.g. Dal lake.


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DYSTROPHIC LAKES: Dystrophic lakes are those that have low pH, highhumic acid content and brown waters e.g. bog lakes.

ENDEMIC LAKES: Endemic lakes are those that are very ancient, deepand have endemic fauna, which are restricted only to that lake e.g. the

lake Baikal in Russia.

ARTIFICIAL LAKES OR IMPOUNDMENTS: Artificial lakes are those lakesthat are created due to construction of dams e.g. Govindsagar Lake at

Bhakra-Nangal.

STREAMS:These are freshwater aquatic ecosystems where water current is a major

controlling factor, oxygen and nutrient in the water is more uniform and land

water exchange is more extensive. Although stream organisms have to face more

extremes of temperature and action of currents as compared to pond or lake

organisms, but they do not have to face oxygen deficiency under natural

conditions. This is because the streams are shallow; have a large surface exposed

to air and constant motion, which churns the water and provides abundant

oxygen. Their dissolved oxygen level is higher than that of ponds even though the

green plants are much less in number. The stream animals usually have a narrow

range of tolerance to oxygen. That is the reason why they are very susceptible to

any organic pollution, which depletes dissolved oxygen in the water. Thus

streams are the worst victims of industrial development.

RIVER ECOSYSTEMS:Rivers are large streams that flow downward from mountain highlands and

flowing through the plains fall into the sea. So the river ecosystems show a series

of different conditions.

THE MOUNTAIN HIGHLAND part has cold, clear waters rushing downas waterfalls with large amounts of dissolved oxygen.

IN THE SECOND PHASEon the gentle slopes, the waters are warmerand support a luxuriant growth of plants and less oxygen requiring

fishes.


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IN THE THIRD PHASE, the river waters are very rich in biotic diversity.Moving down the hill, rivers shape the land. They bring with them

lots of silt rich in nutrients, which are deposited in the plains and in

the delta before reaching the ocean.

WETLANDS:Wetlands are once considered useless and disease ridden places (e.g.,

malaria and yellow fever).

They provide many benefits to society:

Fish and wildlife habitats.

Natural water quality improvement. Flood storage.They also are a source of substantial bio-diversity in supporting major

groups of organisms numerous species from microbes to mammals.

ARTIFICIAL ECOSYSTEMS:They are also called man-made or man-engineered ecosystem. They are

maintained artificially by man where, by addition of energy and plannedmanipulation, natural balance is disturbed regularly, e.g. croplands such as

sugarcane, maize, wheat, rice-fields; orchards, gardens, villages, cities, dams,

aquarium and manned spaceship.

Reference:

ENVIRONMENTAL STUDIES By, Dr. Radha.ECOLOGY By, P.S. Verma & V.K. Agarwal.ENVIRONMENTAL STUDIES By, Arumugam.

Documents

Eco System (Environmental science)