Ecosystems
Introduction:
The High Peaks Wilderness Area in the Adir Adirondack ondack 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 entities composed of the biological community 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 relea sed into the soil, atmosphere and a nd hydrologic system. Afte r a short time of recovery, the community that was once large mature trees now becomes a community community of grasses, herbace ous species, and a nd tree seedlings. Pranav H. Vashi
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Ecosystems
Ecology
deals with several levels of biological organization, population s, communities, ecosystem ecosystem s, biomes and the biosphere.
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including
organisms,
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Ecos
st
s
The si si lest est level evel of organiz organizaation tion in Ecosyst Ecosystem is that hat of the organi organism. An organi organism refers to a par ticu ticullar organi organism in an ecosyst ecosystem, say cat cat, dog et etc. A popul population tion incl ncludes all all the members of t of the same organi organism that hat live live in one pl place at at one time. time. All All the di different fferent popul populations tions that hat live live in a par ticu ticullar area make up a communit community. y. The physi physical cal locati ocation on of a Communit ommunity y is call called ed the habit habitaat. Ecosyst Ecosystem is in turn a level evel of organiz organizaation tion and has one hi higher level evel of organiz organizaati on call called ed biosphere. The phot photograph on the next next page der ived from a forei foreign ecol ecology book woul would clear ly illus illusttrat rate the var ious level evels of organiz organ izaation. tion. The di diversit versity y of an ecosyst ecosystem is a measure of the number of di different fferent speci species there, and how common each speci species is. Ecosyst Ecosystems are very compl complex. They can cont contain hundreds or even thousands of i of interacti eracting ng speci species. Each organi organism or speci species in the communit community y has a rol role or professi profession in that hat communit community y and in ecol ecology this is the organi organism¶s ni niche.
Classifi Classifi ati
f E system system
An ecosyst ecosystem can be cl classi assif ied as bel below
ECOSYSTEM
NATU TUR RAL ECO COSY SYS STE TEM M
TERRESTRIAL ECOSYSTEM
AQUATIC ECOSYSTEM
Forests Grasslands Deserts
Fresh Waters Marine Waters
ARTI AR TIFI FICI CIA AL ECO COSY SYS STE TEM M
There are fur ther cl classi assif icati cations ons in the above char t, but but for a begi beginner l nner level evel, it is enough to concent concentrat rate on these areas. Al Also the st study of ar tif tif icial ecosyst ecosystem is not not the scope of an envi environment ronmental sci scienti entisst. The envi environment ronmentalis lists deal deal with ith nat na tural ural creati creations ons and management management onl only. Moreover the syst system in ar tif tif icial ecosyst ecosystem does not not offer much to study. Therefore we are more interest erested in nat natural ural ecosyst ecosystem and don¶t don¶t consi consider ar tif tif icial ecosyst ecosystem Pranav Pranav H. Vas
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Ecos
st
s
system Approach t o E co system ith With
an ecosyst ecosystem compr ising of l of large number of spec es, it woul would seem and
is impracti mpractica call to study the interacti eraction on of each organi organism with ith anot another,
t is impossi mpossi bl ble
to approach an ecosyst ecosystem by st studyi udying the indi ndividual dual organi organism ± envi environment ronmen t rel relationsh tionshii p. p. Therefore we st study an ecosyst ecosystem foll follow owiing a whol wholesome approach. We study the ecosystems by studying the two aspects (attributes) of an ecosystem. They are
ructure Struct
or Archit Architec ecttural ural Process Functi unction on or Work ing Process Both
processes help to understand the concept of ecosystem in simplif ied
manner.
The architectural process classif ies ecosystem into biotic and abiotic comp onents while the working process help to understand the interaction of ecosys tem components at diff erent levels. Let us understand more about these approaches to
understand Ecosystem.
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Ecos
STRUCTURE
st
s
OF AN ECOSYSTEM
By
Archit Architec ectture or Struct ructure of an Ecosyst Ecosystem, we mean
The compositi composition on of bi biologi ogical cal communit community y incl ncludi uding speci species, numbers, bi biomass, life life hi history and di distr i buti bution on in space, et etc.
The quantit quantity y and di distr i buti bution on of non liv living mat mater ials like like nut nutr ient ents, wat water et etc.
The conditi conditions ons of exi existence such as temperat emperature, lig lig ht etc.
An ecosyst ecosystem possesses bot both liv components and bi biotic factors and living component tic fact nonli nonliv ving or abi abiotic tic fact factors. The nonli nonliv ving fact factors, call called ed abi abiotic tic fact factors, are physi physical cal and chemi chemical cal charact character istics tics of the envi environment ronment. They incl nclude sol solar energy (amount (amount of sun ligh light) t),, oxygen, CO2, wat water, temperat emperature, humi humidity, ity, ph, and avail availab abilit ility y of nit nitrogen. rogen. The liv living component components of the envi environment ronment are call called ed incl nclude all all the Living Thi Things that hat affect affect an organi organism.
Biotic tic
tic Fact actors. Biotic
They
Component omponents are of ten
cat categor ized ized as Producers, Consumers, and Decomposer. The structure of an ecosystem can be represented as below :
ECOSYSTEM ABIOTIC CO COMPONENT S CLIMATIC FACTORS
EDAPHIC FACTORS
E.g. Rain Light Wind Temp.
E.g. Soil Minerals Oxygen Topography
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BIOTIC CO COMPONENTS
PRODUCERS
CONSUMERS
DECOMPOSERS
also known as autotrophs, they produce energy
also known as heterotrophs, they consume and transfer energy
better known as reducers or saptrotrophs recycle energy
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Ecos
st
s
FUNCTION OF AN ECOSYSTEM
The functi function on of an ecosyst ecosystem is a broad, vast vast and of ten confused topi opic. The functi function on of an ecosyst ecosystem can be best best studi udied by underst understandi anding the history of ecol ecologi ogical cal studi udies. The functi function on of an ecosyst ecosystem can be st studi udied under t under the three heads. 1. Trophi Trophic Level Level Int Interacti eraction on 2. Ecol Ecologi ogical cal Successi uccession 3.
ogeochemistry Biogeochemi Trophi Trophic Level Level Int Interacti eraction on deal deals with ith how the members of an ecosyst ecosystem are
connect connected based on nut nutr itiona itionall needs. Ecol Ecologi ogical cal Successi uccession deal deals wit with h the changes in feat features/members of an ecosyst ecosystem over a per iod of ti of time. me.
ogeochemistry Biogeochemi
is focused
upon the cycli cycling ng of essenti essentiaal mat mater ials in an ecosyst ecosystem. Trophi Trophic Level Level Int Interacti eraction on was devel developed by zool oologi ogist Char les Elton. lton. It It deal deals with ith who eat eats who and is eat ea ten by whom in an ecosyst ecosystem. The st study of t of trophi rophic level evel interacti eraction on in an ecosyst ecosystem gives us an idea about about the energy f low through the ecosyst ecosystem. The trophic level interaction involves i nvolves three concepts namely
1.
Food
Chai hain
2.
Food Web
3. Ecol Ecologi ogical cal Pyrami Pyramids
Food Chain:
In an ecosyst ecosystem one can observe the transfer or f low of energy from one trophi rophic level evel to ot o ther i her in successi succession. A trophi rophic level evel can be def ined as the number of li of links nks by whi which it is separat separated from the producer, or as the positi position on of t of the organi organism in the food chai chain. The patt patterns erns of eati eating ng and bei being eat eaten forms a linear linear chai chain call called ed food chai chain whi which can al always be traced back to the producers. Thus, pr imary producers trap radi radiant ant energy of sun and transfer that hat to chemi chemical cal or pot potenti entiaal energy of organi organic compounds such as carbohydrat carbohydrates, prot proteins and fat fats.
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Ecosystems
A food chain always begins with the producer and follow follows s the flow of energy through several levels of consumers. The first order consumers are herbivores who consume p roducers. The second o rder consumer feed on the first order consumers, etc.
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Ecos
When
st
s
an herbi herbivore ani animal mal eat eats a plant ant (or when bact bacter ia decompose it) and these
organi organic compounds are oxi oxidized, ized, the energy li berat berated is just just equal equal to the amount amount of energy used in synt synthesizi hesizing ng the subst substances (f irst rst law of thermodynami hermodynamics) cs), but but some of the energy is heat heat and not not useful useful energy (second law of thermodynami hermodynamics) cs). If this ani animal mal, in rum, is eat eaten by anot another one, al along wit with h transfer of energy from a herbi herb ivore to carni carnivore a fur ther decrease in useful useful energy occurs as a s the second ani animal mal (carni (carnivore) vore) oxi oxidizes izes the organi organic subst substances of the f irst rst (herbi (herbivore or omni omn ivore) vore) to li berat berate energy to synt synthesiz hesizee its its own cell cellu ular constit constituen uentts.
Such
transfer of energy
from organi organism to organi organism sust sustains the ecosyst ecosystem and when energy is transferred from indi ndividual dual to indi ndividual dual in a par ticu ticullar communit community, y, as in a pond or a lake or a r iver, we come across the food chai chains. The number of st steps in a food chai chain is always rest restr icted to four or f ive, si since the energy avail availab ablle decreases wit with h each st step. Many direct rect or indi ndirect rect met methods are empl employed to study food chai chain rel relationsh tionshii ps ps in nat nature. They incl nclude gut gut cont content ent anal analysi ysis, use of radi radioacti oactive ve isot sotopes, preci preci piti pitin n test est, et etc. In nature, basically two types of food chains arc recognized ² grazing food chain and detritus food chain. Grazing food chain: Thi This type of food chai chain star ts from the liv living green pl plant ants
goes to grazi grazing ng herbi herbivores and on to the carni carnivores. Ecosyst Ecosystems wit with h such type of food chai chain are di directl rectly y dependent dependent on an inf lux of sol solar rad iation. tion. Most Most of the ecosyst ecosystems in nat nature foll follow ow this type of food chai chain. organic wast wastes, exudat exudates and dead matt matter er der ived from Detritus food chain: The organi the grazi grazing ng food chai chain are generall generally y termed det detr itus. itus. The energy cont contained in this det detr itus itus in not not lost ost to the ecosyst ecosystem as a whol whole; rat rather it her it serves as the source source of of ene rgy for a group of organi organ isms (Det (Detr itivores itivores)) that hat are separat separate from the grazi grazing ng food chai chain, and generall generally y termed as the det detr itus itus food chai chain Significance
of food chain: The food chai chain studi udies/hel es/hel p under st stand the feedi feeding
rel relationsh tionshii ps ps and the interacti eraction on bet between organi organisms in any ecosyst ecosystem. They al also hel hel p p us to appreci appreciate the energy f low mechani mechanism and matt matter er ci circul rculation tion in eco eco - sys systtem, and underst understand the movement movement of toxi oxic subst substances in the eco-syst eco-system and the probl problem of bi biologi ogical cal magni magnif icati cation on
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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 trophic level le vel i.e i.e it may de rive its food from more than one source. Even the same organism may be eate n 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 ad jacent jacent 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. species.
A more complex food web. Notice that all organisms have arrows connecting to the decomposers. Pranav H. Vashi
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Ecosystems
E ologi ogi
l Pyrami 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 biomass or energy among the different trophic levels of the ecosystem. A trophic level is the the position of an organism in in an ecosystem (producer, first first order order consumer, etc . A pyramid pyramid is used as the model because it shows the decrea se 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 other 90% of energy is mostly lost lost as heat from metabolic metabolic processes and maintenance of daily life functions.
A typical typical trophic pyramid showing showing the decrease in energy available as move from one level to the n ext. In
the successive steps s teps of food chain the number and mass of the organisms in each step is limited by the amount a mount of energy available. available. Since some energy e nergy is lost as heat, in each transformation transformation the steps become progressively smaller near the top. This relationship relationship is sometimes called ecological ecological pyramid. The ecological pyramids pyramids represent the trophic structure and also trophic function of the ecosystem. In many ecological pyramids, pyramids, the producer form the base and the successive succes sive trophic trophic levels make up the apex.
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Ecosystems
E n
rgy Fl ow ow in th
E cosyst
:
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. ecos ystem. rganisms incorporate various elements eleme nts (compounds from the environment into their bodies. When these organisms die, their bodies are broken broken down by decomposers and the compounds are released re leased into the en vironment. vironment. Water Cycl Cycle:
The Water Cycle
The water cycle, c ycle, also called the hydrologic hydrologic cycle, follows follows the continuous path of water. Water enters the vapor phase through evaporation and transpiration transpiration (the release of water vapor from from plants and animals . The sun is the main source 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 wa ter on the planet. Pranav H. Vashi
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Ecosystems
Carbon Cycl Cyc le:
The Carbon Cycle
Carbon dioxide dioxide makes up only 0.03% of the atmosphere but i s the ma j ma jor or source of carbon for additional biomass. Carbon dioxide is converted to organic carbon by photosynthesis in green plants. rganic carbon is then available availa ble to travel through the food web to eventually be released back to the atmosphere by cellular respiration and decomposition. decomposition. Fossil Fuels Fuels are another link link in the the carbon cycle. rganic 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 w ith the increased use of fossil fuels. Pranav H. Vashi
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Ecosystems
Nitrogen
Cycl Cyc le:
The Nitrogen Cycle Nitrogen
comprises approximately 80% of the atmosphere but is not accessible to most life forms. It must be ³fixed´ 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
Cycl Cycle:
The Oxygen Cycle
The oxygen oxygen cycle is very very similar similar to the carbon cycle, but in reverse. reverse. xygen comprises approximately approximately 0% of the atmosphere. xygen 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
E col col ogical ogical II
bal bal anc - I p ril ing ing th
Industrialization exploiting
Ecological
E cosy st
:
Balance
With the increased industriali industriali ation and scientific scientific approach approach to our life, the 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 c hallenges 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
Biodiv
rsity ity & E cosyst cosyst
C ons rvati ation: on:
Biodiversity and
Ecosystem
Biodiversity
and ecosystems sustain each other. They are the living natural capital on which human beings, as one species a mong others, depend for existence and well-being. Biodiversity and ecosystems are the natural basis for the development of sustainable sustainable resource re source uses, including including forestry, farms, rene wable energy, urban land use, fisheries and other 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, ma jor jor 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. Pranav H. Vashi
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