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UNITVILIFE O N THE EARTHThis unit deals with Biosphere — importance of plants and other organisms;ecosystems, bio-geo chemical cycle and ecological balance;biodiversity and conservation2019-2020
CH A P T ERLIFEON THEEARTHBy now you might have realised that allunits of this book have acquainted youwith the three major realms of theenvironment, that is, the lithosphere, theatmosphere and the hydrosphere. You knowthat living organisms of the earth, constitutingthe biosphere, interact with other environmentalrealms. The biosphere includes all the livingcomponents of the earth. It consists of all plantsand animals, including all the microLife on the earth is found almosteverywhere. Living organisms are foundfrom the poles to the equator, from thebottom of the sea to several km in theair, from freezing waters to dry valleys,from under the sea to underground waterlying below the earth’s surface.E COLOGYYou have been reading about ecological andenvironmental problems in newspapers andmagazines. Have you ever thought whatecology is? The environment as you know, ismade up of abiotic and biotic components. Itwould be interesting to understand how thediversity of life-forms is maintained to bring akind of balance. This balance is maintained ina particular proportion so that a healthyinteraction between the biotic and the abioticcomponents goes on.The interactions of a particular group oforganisms with abiotic factors within aparticular habitat resulting in clearly definedenergy flows and material cycles on land, waterand air, are called ecological systems.organisms that live on the planet earth and theirinteractions with the surrounding environment.Most of the organisms exist on the lithosphereand/or the hydrosphere as well as in theatmosphere. There are also many organismsthat move freely from one realm to the other.The biosphere and its components are verysignificant elements of the environment. Theseelements interact with other components of thenatural landscape such as land, water andsoil. They are also influenced by theatmospheric elements such as the temperature,rainfall, moisture and sunlight. Theinteractions of biosphere with land, air andwater are important to the growth,development and evolution of the organism.2019-2020The term ecology is derived from the Greekword ‘oikos’ meaning ‘house’, combinedwith the word ‘logy’ meaning the ‘scienceof’ or ‘the study of ’. Literally, ecology isthe study of the earth as a ‘household’,of plants, human beings, animals andmicro-organisms. They all live togetheras interdependent components. AGerman zoologist Ernst Haeckel, whoused the term as ‘oekologie’ in 1869,became the first person to use the term‘ecology’. The study of interactionsbetween life forms (biotic) and thephysical environment (abiotic) is thescience of ecology. Hence, ecology can bedefined as a scientific study of theinteractions of organisms with theirphysical environment and with each other.
124FUNDAMENTALS OF PHYSICAL GEOGRAPHYA habitat in the ecological sense is the totalityof the physical and chemical factors thatconstitute the general environment. A systemconsisting of biotic and abiotic components isknown as ecosystem. All these components inecosystem are inter related and interact witheach other. Different types of ecosystems existwith varying ranges of environmentalconditions where various plants and animalspecies have got adapted through evolution.This phenomenon is known as ecologicaladaptation.Types of EcosystemsEcosystems are of two major types: terrestrialand aquatic. Terrestrial ecosystem can befurther be classified into ‘biomes’. A biome is aplant and animal community that covers alarge geographical area. The boundaries ofdifferent biomes on land are determined mainlyby climate. Therefore, a biome can be definedas the total assemblage of plant and animalspecies interacting within specific conditions.These include rainfall, temperature, humidityand soil conditions. Some of the major biomesof the world are: forest, grassland, desert andtundra biomes. Aquatic ecosystems can beclassed as marine and freshwater ecosystems.Marine ecosystem includes the oceans,estuaries and coral reefs. Freshwaterecosystem includes lakes, ponds, streams,marshes and bogs.Structure and Functions of EcosystemsThe structure of an ecosystem involves adescription of the available plant and animalspecies. From a structural point of view, allecosystems consist of abiotic and biotic factors.Abiotic factors include rainfall, temperature,sunlight, atmospheric humidity, soilconditions, inorganic substances (carbondioxide, water, nitrogen, calcium, phosphorus,potassium, etc.). Biotic factors include theproducers, the consumers (primary,secondary, tertiary) and the decomposers. Theproducers include all the green plants, whichmanufacture their own food throughphotosynthesis. The primary consumersinclude herbivorous animals like deer, goats,mice and all plant-eating animals. Thecarnivores include all the flesh-eating animalslike snakes, tigers and lions. Certain carnivoresthat feed also on carnivores are known as topcarnivores like hawks and mongooses.Decomposers are those that feed on deadorganisms (for example, scavengers likevultures and crows), and further breakingdown of the dead matter by other decomposingagents like bacteria and various microorganisms.Figure 15.1 : Structure and functions of ecosystems2019-2020
125LIFE ON THE EARTHThe producers are consumed by theprimary consumers whereas the primaryconsumers are, in turn, being eaten by thesecondary consumers. Further, the secondaryconsumers are consumed by the tertiaryconsumers. The decomposers feed on the deadat each and every level. They change them intovarious substances such as nutrients, organicand inorganic salts essential for soil fertility.Organisms of an ecosystem are linked togetherthrough a foodchain (Figure 15.1). Forexample, a plant eating beetle feeding on apaddy stalk is eaten by a frog, which is, in turn,eaten by a snake, which is then consumed bya hawk. This sequence of eating and beingeaten and the resultant transfer of energy fromone level to another is known as the food-chain.Transfer of energy that occurs during theprocess of a foodchain from one level toanother is known as flow of energy. However,food-chains are not isolated from one another.For example, a mouse feeding on grain maybe eaten by different secondary consumers(carnivores) and these carnivores may be eatenby other different tertiary consumers (topcarnivores). In such situations, each of thecarnivores may consume more than one typeof prey. As a result, the food- chains getinterlocked with one another. This interconnecting network of species is known as foodweb. Generally, two types of food-chains arerecognised: grazing food-chain and detritusfood-chain. In a grazing food-chain, the firstlevel starts with plants as producers and endswith carnivores as consumers at the last level,with the herbivores being at the intermediatelevel. There is a loss of energy at each levelwhich may be through respiration, excretionor decomposition. The levels involved in a foodchain range between three to five and energyis lost at each level. A detritus food-chain isbased on autotrophs energy capture initiatedby grazing animals and involves thedecomposition or breaking down of organicwastes and dead matter derived from thegrazing food-chain.Types of BiomesIn the earlier paragraphs, you have learnt themeaning of the term ‘biome’. Let us now try toidentify the major biomes of the world. Thereare five major biomes — forest, desert, grassland,aquatic and altitudinal biomes. Some featuresof these biomes are given in Table 15.1.Biogeochemical CyclesThe sun is the basic source of energy on whichall life depends. This energy initiates lifeprocesses in the biosphere throughphotosynthesis, the main source of food andenergy for green plants. During photosynthesis,carbon dioxide is converted into organiccompounds and oxygen. Out of the total solarinsolation that reaches the earth’s surface, onlya very small fraction (0.1 per cent) is fixed inphotosynthesis. More than half is used for plantrespiration and the remaining part istemporarily stored or is shifted to otherportions of the plant.Life on earth consists of a great variety ofliving organisms. These living organisms existand survive in a diversity of associations. Suchsurvival involves the presence of systemic flowssuch as flows of energy, water and nutrients.These flows show variations in different partsof the world, in different seasons of the yearand under varying local circumstances. Studieshave shown that for the last one billion years,the atmosphere and hydrosphere have beencomposed of approximately the same balanceof chemical components. This balance of thechemical elements is maintained by a cyclicpassage through the tissues of plants andanimals. The cycle starts by absorbing thechemical elements by the organism and isreturned to the air, water and soil throughdecomposition. These cycles are largelyenergised by solar insolation. These cyclicmovements of chemical elements of thebiosphere between the organism and theenvironment are referred to as biogeochemicalcycles. Bio refers to living organisms and geoto rocks, soil, air and water of the earth.There are two types of biogeochemicalcycles : the gaseous and the sedimentary cycle.In the gaseous cycle, the main reservoir ofnutrients is the atmosphere and the ocean. Inthe sedimentary cycle, the main reservoir is thesoil and the sedimentary and other rocks ofthe earth’s crust.The Water CycleAll living organisms, the atmosphere and thelithosphere maintain between them a2019-2020
126FUNDAMENTALS OF PHYSICAL GEOGRAPHYTable 15.1 : World nnahTemperateSteppeA.B.SoilFlora and FaunaA1. Temp. 20-25 C,evenly distributedA2. Temp. 25-30 C,Rainfall, ave. ann.1,000mm, seasonalB. Temp. 20-30 C,Rainfall evenlydistributed 7501,500mm, Welldefined seasonsand distinct winter.C. Short moist moderately warmsummers and longcold dry winter;very lowtemperatures.Precipitation mostlysnowfall400 -1,000mmA1. Acidic,poor innutrientsA2. Rich innutrientsB. Fertile,en-richedwithdecayinglitterC. Acidic andpoor innutrients,thin soilcoverA1. M u l t i - l a y e r e dcanopy tall andlarge treesA2. Less dense, treesof medium height;many varieties coexist. Insects,bats, birds andmammals arecommon speciesin bothB. Moderately densebroad leaved trees.With less diversityof plant species.Oak, Beach, Mapleetc. are somecommon species.Squirrels, rabbits,skunks, birds,blackbears,mountain lions etc.C. Evergreen coniferslike pine, fur andspruce etc. Woodpeckers, hawks,bears, wolves,deer, hares andbats are commonanimalsS a h a r a ,Kalahari,Marusthali,Rub-el-KhaliMarginal areasof hot desertsAtacamaTundra climaticregionsA. Temp. 20 - 45 C.B. 21 - 38 C.C. 15 - 35 C.D. 2 - 25 CA-D Rainfall is less than50 mmRich innutrients withlittle or noorganic matterA-C. Scanty vegetation; few largemammals,insects, reptilesand birdsD. Rabbits, rats,antelopesand groundsquirrelsLarge areasof A f r i c a ,Australia,SouthAmerica andIndiaP a r t s ofEurasia andNorth AmericaA.A.A.A1. 10 N-SA2. 10 - 25 N-SB. Eastern NorthAmerica, N.E.Asia, Westernand CentralEuropeC. Broad belt ofEurasia andNorth America(parts ofSiberia,Alaska,Canada andScandinavia)Hot and Dry A.desertB. Semi ariddesertC. CoastalB.desertD. Cold desert C.D.Grassland A.ClimaticCharacteristicsRegionsB.Warm hotclimates, Rainfall500-1,250 mmHot summers andcold winter.Rainfall 500 900 mmB.Porous withthin layer ofhumus.Thin flocculated soil,rich in basesB.2019-2020Grasses; treesand large shrubsabsent; giraffeszebras, buffalos,leopards, hyenas,elephants, mice,moles, snakesand worms etc.,are commonanimalsGrasses; occasional treessuch as cottonwoods, oaks andwillows; gazelles,zebras, rhin-
127LIFE ON THE EARTHoceros,wildhorses, lions,varieties of birds,worms, snakesetc., are commonanimalsAquaticA.B.Freshwater A.MarineB.Altitudinal———Lakes, streams, A-B Temperatures vary A. Water, swampsriversandwidely with cooler airand marsheswetlandstemperatures andOceans, coralhigh humidityB. Water, tidalreefs, lagoonsswamps andand estuariesmarshesSlopes of highmountain rangeslike the Himalayas,the Andes and theRockiesTemperature andprecipitation varydepending uponlatitudinal zonecirculation of water in solid, liquid or gaseousform referred to as the water or hydrologic cycle(Chapter 13 of this book).Regolith overslopesAlgal and other aquaticand marine plantcommunities withvarieties of waterdwelling animalsDeciduous to tundravegetation varyingaccording to altitudedioxide and are returned to the atmosphere(Figure 15.2).The Carbon CycleCarbon is one of the basic elements of all livingorganisms. It forms the basic constituent ofall the organic compounds. The biospherecontains over half a million carbon compoundsin them. The carbon cycle is mainly theconversion of carbon dioxide. This conversionis initiated by the fixation of carbon dioxidefrom the atmosphere through photosynthesis.Such conversion results in the production ofcarbohydrate, glucose that may be convertedto other organic compounds such as sucrose,starch, cellulose, etc. Here, some of thecarbohydrates are utilised directly by the plantitself. During this process, more carbon dioxideis generated and is released through its leavesor roots during the day. The remainingcarbohydrates not being utilised by the plantbecome part of the plant tissue. Plant tissuesare either being eaten by the herbivorousanimals or get decomposed by the microorganisms. The herbivores convert some of theconsumed carbohydrates into carbon dioxidefor release into the air through respiration. Themicro-organisms decompose the remainingcarbohydrates after the animal dies. Thecarbohydrates that are decomposed by themicro-organisms then get oxidised into carbonFigure 15.2 : Carbon CycleThe Oxygen CycleOxygen is the main by-product ofphotosynthesis. It is involved in the oxidationof carbohydrates with the release of energy,carbon dioxide and water. The cycling ofoxygen is a highly complex process. Oxygenoccurs in a number of chemical forms andcombinations. It combines with nitrogen toform nitrates and with many other mineralsand elements to form various oxides such asthe iron oxide, aluminium oxide and others.Much of oxygen is produced from thedecomposition of water molecules by sunlight2019-2020
128FUNDAMENTALS OF PHYSICAL GEOGRAPHYduring photosynthesis and is released in theatmosphere through transpiration andrespiration processes of plants.The Nitrogen CycleNitrogen is a major constituent of theatmosphere comprising about seventy-eightper cent of the atmospheric gases. It is also anessential constituent of different organiccompounds such as the amino acids, nucleicacids, proteins, vitamins and pigments. Onlya few types of organisms like certain species ofsoil bacteria and blue green algae are capableof utilising it directly in its gaseous form.Generally, nitrogen is usable only after it isfixed. Ninety per cent of fixed nitrogen isbiological. The principal source of free nitrogenis the action of soil micro-organisms andassociated plant roots on atmospheric nitrogenfound in pore spaces of the soil. Nitrogen canalso be fixed in the atmosphere by lightning andcosmic radiation. In the oceans, some marineanimals can fix it. After atmospheric nitrogenhas been fixed into an available form, greenplants can assimilate it. Herbivorous animalsfeeding on plants, in turn, consume some of it.Dead plants and animals, excretion ofnitrogenous wastes are converted into nitritesby the action of bacteria present in the soil.Some bacteria can even convert nitrites intonitrates that can be used again by green plants.There are still other types of bacteria capableof converting nitrates into free nitrogen, aprocess known as denitrification (Figure 15.3).Figure 15.3 : Nitrogen CycleOther Mineral CyclesOther than carbon, oxygen, nitrogen andhydrogen being the principal geochemicalcomponents of the biosphere, many otherminerals also occur as critical nutrients forplant and animal life. These mineral elementsrequired by living organisms are obtainedinitially from inorganic sources such asphosphorus, sulphur, calcium and potassium.They usually occur as salts dissolved in soilwater or lakes, streams and seas. Mineral saltscome directly from the earth’s crust byweathering where the soluble salts enter thewater cycle, eventually reaching the sea. Othersalts are returned to the earth’s surface throughsedimentation, and after weathering, they againenter the cycle. All living organisms fulfill theirmineral requirements from mineral solutionsin their environments. Other animals receivetheir mineral needs from the plants and animalsthey consume. After the death of livingorganisms, the minerals are returned to the soiland water through decomposition and flow.Ecological BalanceEcological balance is a state of dynamicequilibrium within a community of organismsin a habitat or ecosystem. It can happen whenthe diversity of the living organisms remainsrelatively stable. Gradual changes do takeplace but that happens only through naturalsuccession. It can also be explained as a stablebalance in the numbers of each species in anecosystem. This occurs through competitionand cooperation between different organismswhere population remains stable. This balanceis brought about by the fact that certain speciescompete with one another determined by theenvironment in which they grow. This balanceis also attained by the fact that some speciesdepend on others for their food andsustenance. Such accounts are encounteredin vast grasslands where the herbivorousanimals (deer, zebras, buffaloes, etc.) are foundin plenty. On the other hand, the carnivorousanimals (tigers, lions, etc.) that are not usuallyin large numbers, hunt and feed on theherbivores, thereby controlling theirpopulation. In the plants, any disturbance inthe native forests such as clearing the forestfor shifting cultivation usually brings about a2019-2020
129LIFE ON THE EARTHchange in the species distribution. This changeis due to competition where the secondaryforest species such as grasses, bamboos orpines overtakes the native species changingthe original forest structure. This is calledsuccession.Ecological balance may be disturbed dueto the introduction of new species, naturalhazards or human causes. Human interferencehas affected the balance of plant communitiesleading to disturbances in the ecosystems.Such disturbances bring about numeroussecondary successions. Human pressure onthe earth’s resources has put a heavy toll onthe ecosystem. This has destroyed its originalityand has caused adverse effects to the generalenvironment. Ecological imbalances havebrought many natural calamities likefloods, landslides, diseases, erratic climaticoccurrences, etc.There is a very close relationship betweenthe plant and animal communities withinparticular habitats. Diversity of life in aparticular area can be employed as anindicator of the habitat factor. Properknowledge and understanding of such factorsprovide a strong base for protecting andconserving the ecosystems.EXERCISES1.Multiple choice questions.(i) Which one of the following is included in biosphere?(a) only plants(c) only animals(b) all living and non-living organisms(d) all living organisms(ii) Tropical grasslands are also known as :(a) the prairies(c) the steppes(b) the savannas(d) none of the above(iii) Oxygen combines with iron found in the rocks to form :(iv)2.(a) iron carbonate(c) iron oxides(b) iron nitrites(d) iron sulphateDuring photosynthesis, carbon dioxide combines with water in thepresence of sunlight to form :(a) proteins(c) carbohydrates(b) amino acids(d) vitaminsAnswer the following questions in about 30 words.(i) What do you understand by the term ‘ecology’?(ii) What is an ecological system? Identify the major types of ecosystems inthe world.(iii) What is a food-chain? Give one example of a grazing food-chain identifyingthe various levels.(iv) What do you understand by the term ‘food web’? Give examples.(v) What is a biome?2019-2020
130FUNDAMENTALS OF PHYSICAL GEOGRAPHY3.Answer the following questions in about 150 words.(i) What are bio-geochemical cycles? Explain how nitrogen is fixed in theatmosphere.(ii) What is an ecological balance? Discuss the important measures neededto prevent ecological imbalances.Project Work(i) Show the distribution of the different biomes on the outline map of theworld with a note highlighting the important characteristics of each biome.(ii) Make a note of trees, shrubs and perennial plants in your school campusand devote half a day to observe the types of birds which come to thegarden. Can you describe the diversity of birds?2019-2020
Desert A. Hot and Dry desert B. Semi arid desert C. Coastal desert D. Cold desert Grassland A. Tropical Savannah B. Temperate Steppe A1. 10 N-S A2. 10 -25 N-S B. Eastern North America, N.E. Asia, W estern and Central Europe C. Broad belt of Eurasia and North America (parts of Siberia, Alaska, Canada a
May 02, 2018 · D. Program Evaluation ͟The organization has provided a description of the framework for how each program will be evaluated. The framework should include all the elements below: ͟The evaluation methods are cost-effective for the organization ͟Quantitative and qualitative data is being collected (at Basics tier, data collection must have begun)
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Chính Văn.- Còn đức Thế tôn thì tuệ giác cực kỳ trong sạch 8: hiện hành bất nhị 9, đạt đến vô tướng 10, đứng vào chỗ đứng của các đức Thế tôn 11, thể hiện tính bình đẳng của các Ngài, đến chỗ không còn chướng ngại 12, giáo pháp không thể khuynh đảo, tâm thức không bị cản trở, cái được
Le genou de Lucy. Odile Jacob. 1999. Coppens Y. Pré-textes. L’homme préhistorique en morceaux. Eds Odile Jacob. 2011. Costentin J., Delaveau P. Café, thé, chocolat, les bons effets sur le cerveau et pour le corps. Editions Odile Jacob. 2010. Crawford M., Marsh D. The driving force : food in human evolution and the future.
Le genou de Lucy. Odile Jacob. 1999. Coppens Y. Pré-textes. L’homme préhistorique en morceaux. Eds Odile Jacob. 2011. Costentin J., Delaveau P. Café, thé, chocolat, les bons effets sur le cerveau et pour le corps. Editions Odile Jacob. 2010. 3 Crawford M., Marsh D. The driving force : food in human evolution and the future.
