ENVIRONMENTAL SCIENCE

MODULE - 1

ECOSYSTEM

ENVIRONMENT

Nature and human beings are closely related. In fact, the very existence of human life depends on the nature or environment. Environment means all the living and non-living things around us such as Animals, Plants, Forests, Farms, Continents, Oceans, Clouds, Ice caps, Rivers, Structures, Urban centres, Living places, etc. The environment may be defined as an outer physical and biological system in which man and other organisms live with many interacting components. Or in another words

“The sum total of all surroundings of a living organism, including physical, biological and chemical factors, which provide conditions for development and growth of that living organism.”

There is a close interaction among various components which seem to produce some kind of equilibrium in the scheme of nature, what is usually termed as ecological balance. We depend completely on the environment for survival. Natural systems have been degraded by pollution, soil erosion, species extinction etc. by this environmental changes it threaten our long term well-being and survival.

ENVIRONMENTAL SCIENCE

It is the systematic study of how the natural world works, how the environment affects humans and vice versa or the interrelationship or interaction between living beings and environment. Or it can be taken as an integrated approach to addressing environmental problems. We need to understand our interaction or relationship with the environment to creatively solve environmental problems. That’s why environmental science has a prime importance. Identifying a problem is the first step in solving it and environmental science does that.

ECOLOGY

Ecology is the science that deals with the various principles, which govern the relationship and interdependence between the organisms and their environment. The term ecology is derived from two Greek words, Oikos and Logos. Oikos means home or habitation or a place to live in. Logos means study or discourse. Hence, literally speaking, ecology is the study of organisms in their own habitat or the ecology has been defined as the study of structure and functions of nature. Ecology has been broadly divided in to autecology and synecology. Autecology deals with the relationship of one species of organism. An Autecologist studies the life history, population, dynamics, behaviour, home range of a single species. Synecology deals with the ecological studies of communities or an entire ecosystem. It describes the overall energy and material flow through the system.

The main objectives of ecology is to study the relationships between living organism and environment, analyse the interdependence between organisms and environmental components, evolve scientific approaches for controlling and regulating the welfare of living organisms, study the conservation and management of natural resources and environmental pollution. It is the main focus of applied ecology, observe the biological productivity of physical environment or nature and how the products may best serve the mankind or improve the quality of man. It is the main aim of ecosystem ecology.

ECOSYSTEM

No organism or a species live alone and there are associates influencing each other and organizing themselves into communities. The organisms of any community besides interacting among themselves always have functional relationship with the external world or the environment. This “structural and functional system of communities of living organisms and their environment is called ecological system or in short the ecosystem”. The concept of ecosystem was first proposed by A G Tansley (1935). The fundamental principle of ecosystem is that at any place where organisms live, there is a continuous interaction between plants, animals and their environment to produce and exchange materials. OR In other words, an ecosystem can be defined as “The biotic (living) community and its physical (non-living) environment in which matter cycles and energy flows is called ecosystem.” An ecosystem is the smallest unit of biosphere (The regions of the surface and atmosphere of the planet occupied by living organisms). A pond, lake, desert, grassland, forest are common examples of ecosystems.

TYPES OF ECOSYSTEM

The ecosystem is generally divided into, natural ecosystem and artificial ecosystem based on the nature that is the interference of man.

NATURAL ECOSYSTEM

This system function itself under natural conditions without any interference of humans. On the basis of a particular type of habitat (the physical environment in which organism lives), it is further subdivided as terrestrial ecosystem and aquatic ecosystem. Terrestrial ecosystem is often defined by the vegetation type that dominates the community. Terrestrial vegetation has a rapid change of oxygen, water and carbon dioxide. It includes grassland ecosystem, forest ecosystem, desert ecosystem, cropland ecosystem. Aquatic ecosystem includes Fresh Water Ecosystem (Pond ecosystem) and Marine Ecosystem (Deep Seas, Estuaries and Sea shores). Aquatic ecosystem is sub-divided into two, Running Water (Lotic) ecosystem, in this there is a greater horizontal movement of water. These are called channel type habitats. Examples: streams and rivers. Stationary Water (Lentic) ecosystem in these the circulation of water is slow and usually of vertical type. Examples: ponds, lakes, ditch, swamp, etc.

ARTIFICIAL OR MAN ENGINEERED ECOSYSTEM

Artificial ecosystems are maintained by man himself fully or partially through planned manipulations.  For example, man tries to control the biotic community and physic-chemical environment. The examples of such ecosystems are:

  • A pond constructed as a part of waste water treatment plant.
  • Cropland ecosystem such as a field of maize, wheat, rice, etc.
  • Micro ecosystem such as those made in laboratories for a planned study.

STRUCTURE OF AN ECOSYSTEM

The structure of an ecosystem is formed of two components, namely, abiotic factors and biotic factors. Abiotic components constitute the non-living components of the ecosystem and are composed of Physical or Climate factors such as soil, air, water, sunlight, temperature, pressure and humidity, and Chemical factors constituting the inorganic and organic substances. The inorganic substances include Oxygen, Carbon, Hydrogen, Nitrogen Phosphorous, Potassium, Calcium, Sodium, Sulphur etc. that are involved in mineral (nutrients) cycle. The organic substances include carbohydrates and proteins. Biotic components include the living components of the ecosystem and are made of many different populations of species, which are interdependent upon each other in the ecosystem. The biotic factors of an ecosystem are classified into three main groups. They are producers, consumers, and decomposers.

PRODUCERS OR AUTOTROPHS

Producers are the organisms which can prepare their own food from simple inorganic substances like carbon dioxide and water in the presence of sunlight. Terrestrial ecosystems have trees, shrubs, herbs grasses and mosses that contribute within varying degrees to the production. Algae of various types are the most important producers of aquatic ecosystem, although in estuaries and mashes, grasses may be important as producers.  The members of autotrophic (Self Feeding) components are self-nourishing. These are of two types; the first one is Phototrophs, which prepare food through photosynthesis by using solar radiation. e.g. Green plants, Phytoplankton etc. The second one is Chemotrophs, which prepare food through chemosynthesis from inorganic substances by oxidation. e.g. Some Bacteria.

CONSUMERS OR HETEROTROPHS

Consumers are the living members of the ecosystem which consume the food produced by the producers i.e. heterotrophs, means feed on others. They are further divided into three types. Herbivores, they eat the producers like plants and algae. They are also called primary consumers, for e.g. Rabbit, Deer, Elephant, etc., Carnivores, they kill and eat the herbivores. As these carnivores directly depend on herbivores, they are specifically called as primary carnivores or secondary consumers. Fox, wolf, etc., are the secondary consumers in a terrestrial ecosystem. The carnivores which kill and eat the primary carnivores or secondary consumers are called as secondary carnivores or tertiary consumer, for example, lion, tiger, etc., There is an another category called Omnivores:  An animal (Consumer) that eats a variety of food of both plant and animal is known as omnivores. e.g., Humans.

DECOMPOSERS OR SAPROTROPHS

The decomposers are the organisms which decompose the dead bodies of plants, animals and their waste products. They feed on organic compound of dead or living protoplasm of plants and animals for their food and energy. They secrete enzyme which digest the dead organisms and the debris and convert them into smaller molecules. These substances which are released into the environment are consumed by the producers. If there were no decomposers, then the dead bodies of plants and animals would have been kept as it is for ages and the component constituting the bodies of plants and animal would never had returned to their original pools like soil, air and water. e.g. Fungi and certain Bacteria.

PHYTOPLANKTONS

They are the producers present in the aquatic ecosystem. Phytoplankton is the plant like organisms of the water that carry out photosynthesis and float in the upper areas of the world’s ocean. Phytoplankton, also known as microalgae, are similar to terrestrial plants in that they contain chlorophyll to capture sunlight, and they use photosynthesis to turn it into chemical energy in order to live and grow. Phytoplankton is responsible for most of the transfer of carbon in the carbon dioxide from the atmosphere to the ocean. Worldwide, this “biological carbon pump” transfers about 10 gigatonnes of carbon from the atmosphere to the deep ocean each year. Even small changes in the growth of phytoplankton may affect atmospheric carbon dioxide concentrations, which would feed back to global surface temperatures.

A wide variety of adaptations help them stay afloat. Some have their flagellas, fins and spines that act as water wings. Some others store extra food as oil, which buoys them up near the surface. When phytoplankton becomes full of oil, they die and sink to the bottom. They become buried under mud and sand. Over millions of years, heat and pressure within the earth transforms the oil from the algae into crude-oil deposits that can later be used by humans. During normal years, the Earth's oceans go through a process known as upwelling in which the easterly winds blow across the equator and drag the warm surface water with them. Then the denser, colder water from the depths of the ocean rises, restoring oxygen and allowing mineral nutrients to return to the surface where phytoplankton can use them once again.

The two main classes of phytoplankton are Diatoms and Dinoflagellates. When too many nutrients are available, dinoflagellates can bloom or explosively grow to huge numbers and form harmful algal blooms, these blooms can produce extremely powerful bio-toxin compounds that can kill marine life and people who eat contaminated sea food and results in Red tide. Diatoms are dominant members of the phytoplankton, they are especially common in temperate, coastal and polar regions. Dinoflagellates are found throughout the world’s oceans, but tend to prefer warmer areas.

PHOTOSYNTHESIS

No animal can utilize the solar energy directly for its life activities. The green plants can utilize the solar energy to prepare food because they contain chlorophyll which can trap solar energy. During the process of photosynthesis the plants utilize carbon dioxide, water and sunlight, in the presence of chlorophyll to build up complex carbohydrate molecules. In these carbohydrate molecules the solar energy is trapped as potential chemical energy. Thus, solar energy is introduced into the biosphere through photosynthesis. Photosynthesis is one of the most important natural processes, which converts the radian energy into chemical energy and links the non-living world with living world.

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 Fig.3. Photosynthesis.

“Photosynthesis is the phenomenon of synthesis of carbohydrates (mostly glucose) by photoautotrophs (producers - green plants in terrestrial ecosystem and phytoplanktons in aquatic ecosystem), from carbon dioxide (CO2) and water (H2O) using enzymes in presence of sunlight and chlorophyll, and releasing oxygen (O2) as a by-product”. This O2 comes from water and not from CO2.                                                                    

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ECOSYSTEM PRODUCTIVITY

Productivity is the rate of biomass production. It is expressed in terms of g–2yr–1 or (kcal m–2) yr–1 to compare the productivity of different ecosystems. Biomass refers to the total weight of living matter and organic material per unit area. Productivity is the rate at which chemical energy is produced in an ecosystem – expressed as gram of organic matter per square meter per year. In other words, ecosystem productivity represents the total amount of energy (organic matter) fixed or stored by the autotrophs per unit time in the ecosystem. Productivity is divided in to two, primary productivity and secondary productivity.

PRIMARY PRODUCTION

Primary production is defined as the amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis. It is expressed in terms of weight or energy. Or Primary productivity means the rate of food produced by producers (autotrophs) or the rate of solar energy trapped at first trophic level. Primary productivity is again classified in to two, Gross primary productivity and Net primary productivity. Gross Primary Productivity (GPP) means the total amount of energy produced by producers (autotrophs) at trophic level one. Or in another words it is the rate at which an ecosystem’s producers convert solar energy into chemical energy as biomass. This gross productivity depends up on photosynthetic capacity of producers and environmental factors including climatic conditions such as temperature, rainfall and total solar radiation and other nutrient materials of the abiotic environment such as nitrogen, phosphorus and sulphur.

Net Primary Production (NPP) represents the amount of energy or organic matter fixed or stored at trophic level one (Producers) after respiration and which is available to higher trophic levels.

Net Primary Productivity = Gross Primary Productivity – Respiration Rate (Rate at which producers use biomass)

The primary productivity of a natural ecosystem largely depends on the amount of solar radiation; there is positive correlation between primary productivity and solar radiation. Since there is marked decrease in solar radiation received at the earth’s surface from equator towards the poles, primary productivity also, on an average (besides a few intermediate zones of exception), decreases markedly towards the poles. This results in spatial variations in primary productivity at regional and local scales. At a very large scale the primary productivity of the terrestrial ecosystems is far more than the marine ecosystems. E.P Odum (1959) has identified three levels of productivity at world scale as:

  1. The regions of high ecological productivity represented by shallow water areas, moist forest (tropical and temperate), alluvial plains and regions of intensive farming.
  2. The regions of low ecological productivity represented by arctic snow-covered wastelands deserts and deep ocean areas.
  3. Regions of intermediate ecological productivity e.g., grasslands, shallow lakes and farmlands except intensively cultivated areas.

Tropical rainforest have highest primary productivity and is least in desert. In aquatic ecosystem primary productivity is limited by light.

SECONDARY PRODUCTION

The potential energy resulting from primary production furnishes the energy required by other trophic levels in an ecosystem. Some energy in the form of food is consumed by herbivores or omnivores which may be eaten by carnivores which in turn may be eaten by other carnivores. However, much of this ingested food is not assimilated; herbivores may assimilate only 10 per cent of the ingested food, whereas the unassimilated materials leave the animal’s body as waste materials to serve as energy source for other organisms. Assimilated energy is used by the consumers for various metabolic processes like respiration, excretion, reproduction etc. The resultant amount of energy stored in the tissues of heterotrophs is termed as net Secondary Production.

In terrestrial ecosystems the order of productivity in decreasing order is 1. Swamps, marshes, tropical rain forests (most productive), 2.Temperate forest, 3.Northern coniferous forest (taiga), 4. Savanna, 5.Agricultural land, 6.Woodland and shrub land, 7.Temperate grassland, 8.Tundra (arctic and alpine), 9.Desert scrub, 10. Extreme desert (least productive). In Aquatic ecosystems, productivity in decreasing manner is 1.Estuaries (most productive), 2.Lakes and streams, 3.Continental shelf, 4.Open ocean (least productive).

FOOD CHAINS

The biotic factors of the ecosystem are linked together by food. For example, the producers form the food for the herbivores; the herbivores form the food for the carnivores. The sequence of the eaters being eaten is called food chain. “Food chain is the sequence of who eats whom in a biological community (ecosystem) to obtain nutrition” or in another words the transfer of energy in an ecosystem through a series of organisms, by eating and being eaten, constitutes food chains. The position of organisms in the food chain or each step of the food chain is referred as Trophic level. There are two types of food chain.

GRAZING FOOD CHAIN

This food chain starts from producers, passes through herbivores, then to carnivores and decomposers.

  • Grass ° Grass hopper ° Frog ° Snake ° Owl
  • Diatoms ° Crustaceans ° Herrings
  • Phytoplanktons ° Copepod ° Herring

DETRITUS FOOD CHAIN

This chain begins with dead organic matter and ends up with inorganic compounds. There are certain organisms which depend exclusively on the dead bodies of animals and plants. These organisms are called detritivores.

  • Leaf litter ° Earthworm ° Blackbird
  • Dead animal ° Blowfly maggots ° Frog ° Hawk
  • Dead animal ° Earthworm ° Frog ° Snake ° Hawk

FOOD WEB

The various food chains in an ecosystem are interconnected or interlinked with each other to form a network called food web. If the links in the chains that make up the web of life are disrupted due to human activities that lead to the loss or extinction of species, the web breaks down.

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SIGNIFICANCE OF FOOD WEB

Food webs are very important in maintaining the stability of an ecosystem. For example, the deleterious growth of grasses in a grass land is controlled by the herbivores. When one type of herbivore becomes extinct, the other types of herbivores increase in number and control the vegetation. Similarly, when one types of herbivorous animal becomes extinct, the carnivore predating of this type may eat another type of herbivore. Thus, the existence of a food web denotes the self-sustaining capacity of an ecosystem. Some species, if eliminated, seriously affect the ecosystem. These are called keystone species.   

ECOLOGICAL PYRAMIDS

The biotic components of an ecosystem, like the producers, consumers and decomposers have definite relationships with reference to their number, biomass and energy. The graphical representation of the above relationship by pyramids is known as ecological pyramids. Three different types of ecological pyramids that exist among organisms are the pyramid of numbers, the pyramid of biomass and the pyramid of energy.

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THE PYRAMID OF NUMBERS

The number of organisms decreases from producer level to carnivore level. This is called pyramid of number. In most ecosystems the pyramid of number is mostly erect or upright eg. Grass land, but in some cases the pyramid of number is inverted. eg. Numerous insects live on a single huge tree. In this, number of individuals at the trophic level decreases from the producer level to the consumer level.

PYRAMID OF BIOMASS

The biomass generally decreases from producer level to carnivore level. This is called pyramid of biomass. It is mostly upright or erect. eg. Fallow land. In aquatic ecosystem the pyramid of biomass is inverted. eg. The combined weight of phytoplankton in a lake is small as compared to weight of fish.

PYRAMID OF ENERGY

The amount of energy flow decreases from producer level to carnivore level, this is called pyramid of energy. The pyramid of energy is always erect or upright. It indicates the total energy at each trophic level of the food chain. It also exhibits that at each trophic level, loss of energy and material takes place, as the processes of assimilation and growth. Thus, at the producer level, the total energy available is relatively more than at the higher trophic levels.

ECOLOGICAL SUCCESSION

Biological communities in a given landscape have a history of development in that area. The gradual and progressive replacement of one community by another, till the development of a stable community in that area, or a process through which ecosystems tend to change over a period of time is called as ecological succession. Succession can be related to seasonal environmental changes, which create changes in the community of plants and animals living in the ecosystem. The stages in succession - where different communities predominate - are called seres. Theoretically, a community will eventually form which is in complete equilibrium with its physical environment and no further changes will occur to that community - this is then known as the climax community.

The occurrence of ecological succession has following characteristics:

  1. It is systematic process that involves changes in species structure.
  2. The changes are directional and take place as a function of time.
  3. The succession occurs due to changes in physical environment and population of the species.
  4. The changes also occur due to population explosion of the species.
  5. The changes are predictable.

TYPES OF SUCCESSION

PRIMARY SUCCESSION

Primary succession is the simplest type of succession; Primary succession occurs where there was no ecosystem before, beginning with a bare surface with no life or soil present. The bare surface may be rock from a recently erupted volcano or sand dunes or cliffs or even a lake surface. It starts with the arrival of living things such as lichens that do not need soil to survive. The first organisms to colonize the area are known as the pioneer species or community and usually consist of organisms such as cyanophycae, algae and lichens. Pioneer species it is the first organism to colonize any newly available area and begin the process of ecological succession. Over time, the pioneer species makes the area habitable by other species.

SECONDARY SUCCESSION

Secondary succession begins in a place that already has soil and was once the home of living organisms. Occurs faster and has different pioneer species than primary succession. That is, it occurs on a surface where an ecosystem has previously existed and that have been disturbed or disrupted by animals or humans interference such as logging and clear-cutting, or by the result of natural disasters such as fires, floods, storms, earthquakes and volcanoes. Following such destruction, the process of succession will occur again from the new environmental conditions - not from a bare surface and this is known as secondary succession. eg. A natural forest destroyed by fire or clear felling is reoccupied by herbs.

LICHENS

They do not require soil. They are colorful and flaky patches. Lichens composed of two species, algae and fungi. The algae photosynthesize and the fungi absorb nutrients from rocks and holds water, that is they are in symbiotic relationship. Over time, they break down the rock and the forces of weather and erosion help break down rocks into smaller pieces. As the rocks breaks apart, water freezes and thaws on the cracks, this breaks up the rocks further. When the lichens die, they accumulate in cracks. And they decompose, adding small amounts of organic matter to the rock to make soil. Simple plants like mosses and ferns can grow in the new soil. Hence these simple plant die it add more organic material to the soil, which leading to the creation of fertile soil. The fertile soil is made up of the broken rocks, decayed organisms, water, and air. By this the soil layer thickens, and grasses, wildflowers, and other plants begin to take over. These plants die, and they add more nutrients to the soil. Shrubs and trees can survive now. Insects, small birds, and mammals have begun to move in. what was once bare rock now supports a variety of life. Primary succession takes several hundred years to produce fertile soil naturally.

CLIMAX COMMUNITY

A climax community is a mature, stable community that is the final stage of ecological succession. In an ecosystem with a climax community, the conditions continue to be suitable for all the members of the community. Any particular region has its own set of climax species, which are the plants that are best, adapted for the area and will persist after succession has finished, until another disturbance clears the area. eg. Pine trees in forest ecosystem.

ECOLOGICAL BALANCE

Ecological balance is a state of dynamic equilibrium within a community of organisms in which genetic, species and ecosystem diversity remain relatively stable, subject to gradual changes through natural succession. And a stable balance in the numbers of each species. Species in an ecosystem each have a role in keeping the ecosystem running smoothly. For example, predators keep the population of mice under control, insects pollinate flowers, and worms decompose leaf litter. All species are important and help keep the ecosystem balanced. Ecological balance is a term describing how ecosystems are organized in a state of stability where species coexist with other species and with their environment.

Even if an ecosystem is balanced, that does not mean that no changes ever occur. A windstorm might roll through wiping out a swath of trees, a predator might be overhunted, or a drought might reduce the availability of food resources. These ecological changes are called disturbances. A disturbance is any change that causes a disruption in the balance of an ecosystem.

ECOLOGICAL NICHE

An ecological niche is the role and position a species has in its environment (ecosystem); how it meets its needs for food and shelter, how it survives, and how it reproduces. A species niche includes all of its interactions with the biotic and abiotic factors of its environment. The description of a niche may include descriptions of the organism's life history, habitat, and place in the food chain. More formally, the niche includes how a population responds to the abundance of its resources and enemies. The abiotic or physical environment is also part of the niche because it influences how populations affect, and are affected by, resources and enemies.

If you closely look at a typical habitat in the environment, you will see many organisms living and working together, fulfilling their ecological niches. For example, in the forest where there are leaves scattered on the ground and an old rotting log sitting on the forest floor. We can see earthworms just under the soil feeding on decaying organic matter. There could also be centipedes eating small beetles and other organisms as well as a colony of ants that work and feed on dead insects. You may even find a couple of millipedes strolling around feeding on decaying leaves.  In this small section of the vast forest, all of these organisms are filling an individual ecological niche. You could think of each ecological niche as parts of a puzzle that go together to make the environment successful.

FUNCTIONS OF ECOSYSTEM

 An ecosystem performs the following functions:

  •   It allows the flow of biological energy, controls the rate of production, respiration of community.
  •     It controls the rate of nutrient cycle production and consumption of minerals.
  •    It regulates the environment by organism and the organism by environment. For example, Nitrogen fixing by bacteria is the regulation of environment by organism and Photoperiodism (the response of an organism to seasonal changes in day length) is the process of organism regulation by environment.
  •     It allows the circulation of chemical elements from environment to organism and back to the environment. In this way it provides nutrients to the producers, which build-up organic matter.

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ECOLOGICAL FOOTPRINT

The simplest way to define ecological footprint would be to call it the impact of human activities measured in terms of the area of biologically productive land and water required to produce the goods consumed and to assimilate the wastes generated. More simply, it is the amount of the environment necessary to produce the goods and services necessary to support a particular lifestyle. The Ecological Footprint is defined as the area of productive land and water ecosystems required for the production of the resources that the population consumes and assimilate the wastes that the population produces, wherever on Earth the land and water is located. It is the environmental input of a person or population.

BIOMES

Biomes are very large ecological areas on the earth’s surface, with fauna and flora (animals and plants) having similar climate (weather, temperature). In another words biome is defined as the world's major communities, classified according to the predominant vegetation and characterized by adaptations of organisms to that particular environment. There are terrestrial biomes (land) and aquatic biomes, both freshwater and marine. There are five major categories of biomes on earth. In these five, there are many sub-biomes, under which are many more well defined ecosystems.  The major types of biomes are; aquatic, desert, forest, grassland, and tundra.  In these Forests are separated into rainforest, temperate forest, chaparral, and taiga; grasslands are divided into savanna and temperate grasslands; and the aquatic biome is split into freshwater and marine.

ECOTONE

An Ecotone is a transitional area of vegetation between two different ecosystems or plant communities, such as forest and grassland.  In landscape ecology, an ecotone is the border areas where two patches meet that have different ecological composition. The ecotone contains elements of both bordering communities as well as organisms which are characteristic and restricted to the ecotone. Ecotones are not limited to terrestrial communities; for example, the transition from soft bottom to hard bottom marine communities is an aquatic ecotone. Or Ecotones also appear where one body of water meets another (e.g., estuaries and lagoons) or at the boundary between the water and the land (e.g., marshes). Ecotones often have a larger number of species and larger population densities than the communities on either side. This tendency for increased biodiversity within the ecotone is referred to as the "edge effect." Or the influence of the two bordering communities on each other is known as the edge effect.

An ecotone may be created by natural or man-made factors. Natural factors include abiotic factor transitions in soils composition, pH, soil salinity, soil mineral content as well as topographic and meteorological transition zones. Anthropogenic bases of ecotones can be such acts as forest clearing, pollution within a given soil area, over-drafting of groundwater in a well-defined locale, or controlled burning. Ecotones are also dynamic, changing width and positions with time during succession or environmental changes at various scales.

HOME RANGE

Every animal species needs a certain amount of space to survive and thrive. The amount of space an animal uses on a regular basis is called its home range. It is the region that encompasses all the resources the animal requires to survive and reproduce. Competition for food and other resources influences how animals are distributed in space. Home ranges can stretch for many miles or they can be only a few feet. The size of a home range often depends on the size of an animal. Large animals, like the moose, need more space to survive than smaller animals like the chipmunk.

CARRYING CAPACITY

For a given region, carrying capacity is the maximum number of individuals of a given species that an area's resources can sustain indefinitely without significantly depleting or degrading those resources. Determining the carrying capacities for most organisms is fairly straightforward. For humans carrying capacity is much more complicated. The definition is expanded to include not degrading our cultural and social environments and not harming the physical environment in ways that would adversely affect future generations. Carrying capacity is a measure of sustainability with the changing conditions environment.

CONCLUSION

Ecosystem has a great role in the existence of life on earth. Everyone in the world depends completely on Earth’s ecosystems and the services they provide, such as food, water, medicine, climate regulation, spiritual fulfilment, and aesthetic enjoyment. Ecosystem one of the major governing entity of the environment, though tends to stabilize the deficiency and disequilibrium, but with the increasing manipulation of human activities, the ecosystem are turning out to be fragile in nature. Over the past 50 years, humans have changed these ecosystems more rapidly and extensively than in any comparable period of time in human history. Thus, conservation and preservation of ecosystem should be a major concern to all. These problems, unless addressed, will substantially reduce the benefits that future generations obtain from ecosystems.

Ecosystem degradation can rarely be reversed without addressing the five indirect drivers of change: population change (including growth and migration), change in economic activity (including economic growth, disparities in wealth, and trade patterns), socio-political factors (ranging from the presence of conflict to public participation in decision-making), cultural factors, and technological change.

We need the development along with the sustainable use of resources and the development should be ecofriendly. Whatever be the developments, it should be concerned about the environment.

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