Ecosystems

Ecosystems

Introduction:

The High Peaks Wilderness Area in the Adirondack Park is an example of a diverse ecosystem.

An ecosystem can be defined as 'a structural and functional unit of biosphere or segment of nature consisting of community of living beings and the physical environment, both interacting and exchanging materials between them'.

Ecosystems are dynamic entities composed of the biological community and the abiotic environment. An ecosystem's abiotic and biotic composition and structure is determined by the state of a number of interrelated environmental factors. Changes in any of these factors will result in dynamic changes to the nature of these systems. For example, a fire in the temperate deciduous forest completely changes the structure of that system. There are no longer any large trees, most of the mosses, herbs, and shrubs that occupy the forest floor are gone, and the nutrients that were stored in the biomass are quickly released into the soil, atmosphere and hydrologic system. After a short time of recovery, the community that was once large mature trees now becomes a community of grasses, herbaceous species, and tree seedlings.

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Ecosystems

Ecology deals with several levels of biological organization, including organisms, populations, communities, ecosystems, biomes and the biosphere.

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Ecosystems

The simplest level of organization in Ecosystem is that of the organism. An organism refers to a particular organism in an ecosystem, say cat, dog etc. A population includes all the members of the same organism that live in one place at one time. All the different populations that live in a particular area make up a community. The physical location of a Community is called the habitat. Ecosystem is in turn a level of organization and has one higher level of organization called biosphere. The photograph on the next page derived from a foreign ecology book would clearly illustrate the various levels of organization.

The diversity of an ecosystem is a measure of the number of different species there, and how common each species is. Ecosystems are very complex. They can contain hundreds or even thousands of interacting species. Each organism or species in the community has a role or profession in that community and in ecology this is the organism’s niche.

Classification of Ecosystem:

An ecosystem can be classified as below

ECOSYSTEM

NATURAL ECOSYSTEM ARTIFICIAL ECOSYSTEM

TERRESTRIALECOSYSTEMForestsGrasslandsDeserts

AQUATICECOSYSTEMFresh WatersMarine Waters

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

enough to concentrate on these areas. Also the study of artificial ecosystem is not the

scope of an environmental scientist. The environmentalists deal with natural creations

and management only. Moreover the system in artificial ecosystem does not offer

much to study. Therefore we are more interested in natural ecosystem and don’t

consider artificial ecosystem

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Ecosystems

Approach to Ecosystem:

With an ecosystem comprising of large number of species, it would seem and

is impractical to study the interaction of each organism with another, it is impossible to approach an ecosystem by studying the individual organism – environment relationship. Therefore we study an ecosystem following a wholesome approach.

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

Structure or Architectural Process Function or Working Process

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

The architectural process classifies ecosystem into biotic and abiotic components while the working process help to understand the interaction of ecosystem components at different levels. Let us understand more about these approaches to understand Ecosystem.

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Ecosystems

STRUCTURE OF AN ECOSYSTEM

By Architecture or Structure of an Ecosystem, we mean

The composition of biological community including species, numbers,

biomass, life history and distribution in space, etc.

The quantity and distribution of non living materials like nutrients, water etc.

The conditions of existence such as temperature, light etc.

An ecosystem possesses both living components and biotic factors and

nonliving or abiotic factors.

The nonliving factors, called abiotic factors, are physical and chemical

characteristics of the environment. They include solar energy (amount of sun light),

oxygen, CO2, water, temperature, humidity, ph, and availability of nitrogen.

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

include all the Living Things that affect an organism. Biotic Components are often

categorized as Producers, Consumers, and Decomposer.

The structure of an ecosystem can be represented as below:

ECOSYSTEM

ABIOTIC COMPONENTS BIOTIC COMPONENTS

CLIMATICFACTORS

E.g. RainLightWindTemp.

EDAPHIC FACTORS

E.g. SoilMineralsOxygenTopography

PRODUCERS

also known as autotrophs, they produce energy

CONSUMERS

also known as heterotrophs, they consume and transfer energy

DECOMPOSERS

better known as reducers or saptrotrophs recycle energy

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Ecosystems

FUNCTION OF AN ECOSYSTEM

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

function of an ecosystem can be best studied by understanding the history of

ecological studies. The function of an ecosystem can be studied under the three heads.

1. Trophic Level Interaction

2. Ecological Succession

3. Biogeochemistry

Trophic Level Interaction deals with how the members of an ecosystem are

connected based on nutritional needs. Ecological Succession deals with the changes in

features/members of an ecosystem over a period of time. Biogeochemistry is focused

upon the cycling of essential materials in an ecosystem.

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

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

interaction in an ecosystem gives us an idea about the energy flow through the

ecosystem.

The trophic level interaction involves three concepts namely

1. Food Chain

2. Food Web

3. Ecological Pyramids

Food Chain:

In an ecosystem one can observe the transfer or flow of energy from one trophic

level to other in succession. A trophic level can be defined as the number of links by

which it is separated from the producer, or as the position of the organism in the food

chain. The patterns of eating and being eaten forms a linear chain called food chain

which can always be traced back to the producers. Thus, primary producers trap

radiant energy of sun and transfer that to chemical or potential energy of organic

compounds such as carbohydrates, proteins and fats.

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Ecosystems

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

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

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Ecosystems

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

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

energy used in synthesizing the substances (first law of thermodynamics), but some of

the energy is heat and not useful energy (second law of thermodynamics). If this

animal, in rum, is eaten by another one, along with transfer of energy from a herbivore

to carnivore a further decrease in useful energy occurs as the second animal

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

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

from organism to organism sustains the ecosystem and when energy is transferred

from individual to individual in a particular community, as in a pond or a lake or a

river, we come across the food chains. The number of steps in a food chain is always

restricted to four or five, since the energy available decreases with each step. Many

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

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

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

chain and detritus food chain.

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

goes to grazing herbivores and on to the carnivores. Ecosystems with such type of

food chain are directly dependent on an influx of solar radiation. Most of the

ecosystems in nature follow this type of food chain.

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

the grazing food chain are generally termed detritus. The energy contained in this

detritus in not lost to the ecosystem as a whole; rather it serves as the source of energy

for a group of organisms (Detritivores) that are separate from the grazing food chain,

and generally termed as the detritus food chain

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

relationships and the interaction between organisms in any ecosystem. They also help

us to appreciate the energy flow mechanism and matter circulation in eco- system, and

understand the movement of toxic substances in the eco-system and the problem of

biological magnification

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Ecosystems

Food Web:

In nature simple food chains occur rarely the same organism may operate in the ecosystem at more than one trophic level i.e it may derive its food from more than one source. Even the same organism may be eaten by several organisms of a higher trophic level or an organism may feed upon several different organisms of a lower trophic level. Usually the kind of food changes with the age of the organism and the food availability. Thus in a given ecosystem various food chains are linked together and interested each other to form a complex network called food Web. Generally food webs are not too complex. Expect in insect communities, omnivores are scare and when they occur they usually feed on species in adjacent trophic levels. Within habitats, food webs arc rarely broken up into discrete compartments. The number of species of predators in a food web typically exceeds the number of species of prey by an average of 1.3 predator species per prey species.

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

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Ecosystems

Ecological Pyramids:

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

The purpose of a trophic pyramid is to graphically represent the distribution of

biomass or energy among the different trophic levels of the ecosystem. A trophic level

is the position of an organism in an ecosystem (producer, first order consumer, etc). A

pyramid is used as the model because it shows the decrease in energy available as you

go through a food web. The availability of energy decreases as you travel up the

pyramid because only 10% of energy absorbed becomes stored energy (available to

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

maintenance of daily life functions.

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

In the successive steps of food chain the number and mass of the organisms in each step is limited by the amount of energy available. Since some energy is lost as heat, in each transformation the steps become progressively smaller near the top. This relationship is sometimes called ecological pyramid. The ecological pyramids represent the trophic structure and also trophic function of the ecosystem. In many ecological pyramids, the producer form the base and the successive trophic levels make up the apex.

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Ecosystems

Energy Flow in the Ecosystem:

Energy flows through an ecosystem and is ultimately lost to the environment. Matter, on the other hand, is recycled. Matter is finite. If matter was not cycled through the ecosystem, the supply would have been exhausted a long time ago. A simple matter cycle consists of an exchange of matter between living and non-living components of an ecosystem. Organisms incorporate various elements (compounds) from the environment into their bodies. When these organisms die, their bodies are broken down by decomposers and the compounds are released into the environment.

Water Cycle:

The Water Cycle

The water cycle, also called the hydrologic cycle, follows the continuous path of water. Water enters the vapor phase through evaporation and transpiration (the release of water vapor from plants and animals). The sun is the main source of energy that allows the water to undergo a phase change. The water vapor raises, cools, and condenses forming clouds. The water droplets become heavier and eventually fall as precipitation. A small portion of the precipitation will be taken up by the plants and animals more will infiltrate the soil, entering the water table, with the largest portion of the precipitation forming runoff on the surface of the land to drain into streams, rivers, lakes, and ultimately the ocean. The hydrologic cycle is a continuous process that recycles all the water on the planet.

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Ecosystems

Carbon Cycle:

The Carbon Cycle

Carbon dioxide makes up only 0.03% of the atmosphere but is the major source of carbon for additional biomass. Carbon dioxide is converted to organic carbon by photosynthesis in green plants. Organic carbon is then available to travel through the food web to eventually be released back to the atmosphere by cellular respiration and decomposition. Fossil Fuels are another link in the carbon cycle. Organic carbon has been trapped underground for millions of years in the form of coal, oil, and natural gas. This carbon, in the form of carbon dioxide, is released back to the atmosphere by the burning of fossil fuels. Carbon dioxide that is dissolved in the ocean can be absorb by animals and temporarily trapped in their skeletons and shells. It should be noted that humans are altering the carbon cycle with the increased use of fossil fuels.

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Ecosystems

Nitrogen Cycle:

The Nitrogen Cycle

Nitrogen comprises approximately 80% of the atmosphere but is not accessible to most life forms. It must be “fixed” before it can be absorbed. Nitrogen-fixing bacteria are responsible for converting atmospheric nitrogen into its ionic form, ammonium. Ammonium is converted to nitrites and nitrates. Plants can access this nitrate. However, animals must get their nitrogen from the food that they eat. Thus, nitrogen flows through the food web much like carbon. Nitrogen is returned back to the atmosphere through decomposers and then denitrifying bacteria.

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Ecosystems

Oxygen Cycle:

The Oxygen Cycle

The oxygen cycle is very similar to the carbon cycle, but in reverse. Oxygen comprises approximately 20% of the atmosphere. Oxygen is removed from the atmosphere through cellular respiration and returned to the atmosphere by photosynthesis. Large amounts of oxygen are dissolved in large bodies of water.

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Ecosystems

Ecological Imbalance - Imperiling the Ecosystem:

Industrialization exploiting Ecological Balance

With the increased industrialization and scientific approach to our life, the natural resources and rich natural heritage which were being preserved for centuries have begun dwindling greatly. Any kind of imbalance in nature results into severe danger to our ecosystem.

Its treatment with nature has posed today many serious challenges and problems like climate change, vector-borne disease, decay in wildlife and its resources and food and water shortage. Exploitation of natural resources prevalent all over the world has erupted into severe ecological degradation, which is definitely the biggest threat to proper functioning of our ecosystem.

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Ecosystems

Biodiversity & Ecosystem Conservation:

Biodiversity and Ecosystem

Biodiversity and ecosystems sustain each other. They are the living natural capital on which human beings, as one species among others, depend for existence and well-being. Biodiversity and ecosystems are the natural basis for the development of sustainable resource uses, including forestry, farms, renewable energy, urban land use, fisheries and other coastal & marine uses.

Proactive programs to conserve biodiversity include research and management for wild populations and habitats, protected areas, large ecosystems such as Great Lakes, grasslands, forests, wetlands, deserts, major rivers and estuaries, oceans, and more sustainable resource practices. They also include planning, monitoring and enforcement related to land, sea and resource uses, environmental assessment, pollution and species at risk.

The need for conservation action is urgent, nationally and globally. The last two centuries have seen increasing rates of depletion of natural capital, with resulting changes increasingly evident even at global levels, such as climate change, large ecosystem fragmentation and degradation, and species extinctions. There is now a higher level of multilateral and national fora and talk for conservation, but the negative momentum is as yet only barely affected.

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