SOIL QUALITY 1 Soil is a renewable resource, but only on a very long time scale, as it takes hundreds or thousands of years for the natural processes of erosion, organic decay, and accumulation to create soils. Soil quality and the potential to produce crops can vary enormously from region to region and among various soil types. 2 One important factor affecting the productivity of soils over time is agriculture. Top-quality lands are brought into production earlier because of their higher potential to produce food. As more and more land has been brought under agricultural production, the average quality of land has decreased, reducing potential productivity per hectare. Crops deplete soil fertility by consuming nutrients, and this eventually reduces crop yields. Poor management practices lead to soil compaction and soil pollution as well as loss of soil cover. Without proper management and the constant addition of nutrients and energy in the form of fertilizers and irrigation, crop production fails over time. 3 Within the scientific community, there is little doubt that soil quality is diminishing in many areas around the world. Scientists have found that the quality of one quarter of the world"s soils has experienced some loss, and the pace of degradation has accelerated over the past 50 years. The loss of soil fertility has caused a slowing in the growth of agricultural productivity. Annual crops tend to degrade soils more than perennial crops, and common property lands generally suffer more degradation than private lands. 4 Today, irrigated cropland produces about one-third of the world"s food. Approximately 18 percent of the world"s cropland is irrigated, and scientists project this amount to double in the next decade. Irrigation can increase crop yields per hectare to two or three times the yields of land watered only by rain. However, there are also some harmful side effects. Besides increasing crop productivity in the short run, irrigation can lead to sharp drops in crop productivity in the long run by causing excessive salt buildup and rising water tables. 5 One of the most critical soil quality problems related to irrigation is the increase in concentration of dissolved salts. This process, salinization, affects an estimated one-fourth of the world"s irrigated cropland. In some places, irrigation water contains as much as 3.5 tons of salt per 1,000 cubic meters. As the water flows over and through the ground, it dissolves salts, increasing the salinity of the water. Since some crops require 6,000 to 10,000 cubic meters of water per hectare, land can receive tens of tons of salt per hectare. As the water evaporates, high concentrations of salts such as sodium chloride are left behind in the topsoil. Salt buildup can stunt crop growth, decrease yields, kill crop plants, and eventually make the land unproductive. 6 A problem that often accompanies salinization in dry regions is waterlogging, which often occurs when farmers apply heavy amounts of irrigation water in an attempt to prevent salts from accumulating. However, unless the water drains properly, it collects underground and gradually raises the water table closer to the surface, thereby bringing salts to the surface and concentrating them. Saltwater then envelops the fragile root systems of plants, killing the plants and converting fertile fields to wet deserts. This is a particularly serious problem in California"s heavily irrigated San Joaquin Valley, where soils contain a clay layer that prevents water from flowing through the ground. Worldwide, at least one-tenth of all irrigated land is subject to waterlogging. 7 Another serious soil problem is erosion, the loss of soils from water and wind action. Soil erosion occurs on agricultural land without vegetative cover for protection or because of poor agricultural management. Scientists estimate that topsoil on cultivated land is being lost 16 to 300 times faster than it is being replaced. In many parts of the world, a shift away from traditional agricultural practices is placing greater pressure on the soil, which in turn is causing an increase in soil erosion rates. Studies in the United States suggest that the loss of just 2.5 centimeters of topsoil reduces corn and wheat yields by 6 percent.

{{B}}Set 2 Computer Lecture{{/B}} {{B}}Narrator{{/B}} Listen to a conversation between a student and a dean of admissions.

Music to Your Gears Music may soothe the savage breast, but it can also damage your health when you are at the wheel. A. [■] Recent research suggests that loud music seriously affects a driver's concentration and psychologists have warned that such music, blasting away inside a car, can be dangerous, especially in traffic queues or on motorways. B. [■] Heavy metal, with its strong beat, leads to aggressive driving while, at the other end of the spectrum, soothing, melodious music relaxes a driver beyond a safe limit of awareness and into a sleepy haze of inattention. C. [■] The British Automobile Association, which is concerned with road safety, commissioned research into the relationship between serious accidents and music. D. [■] It found that men in the 17-25 age bracket were the most dangerous and accident-prone group. It also found that this group listens to music seventy percent of the time when they are on the move. Upbeat tempos, or heavy metal music, played loudly, can bring on a belligerent attitude. The driving style becomes aggressive and the driver is more apt to take risks. The pace of the driving is governed by the pace and beat of the music. In {{U}}trials{{/U}}, volunteer drivers subjected to loud music said that, although they didn't necessarily feel inclined to drive faster, they did find themselves making faster gear changes, accelerating more quickly and braking more abruptly. The same drivers, when subjected to slow ballads, admitted that they often found their attention wandering and, during a long motorway journey, at least two of the participants found themselves unconsciously wandering across the lane markings. The comments made by the volunteer drivers, some of whom were newly qualified, were very revealing. Simon, eighteen, told the AA, "The fast rock track out of Bat Out of Hell is potentially lethal. I found myself going faster and faster without even realizing it. " Another volunteer, who had been listening to ZZ Top's greatest hits, said, "I was speeding along singing at the top of my voice and didn't see or hear the fire engine that was trying to overtake me. " Other comments included. "I get lost in my own thoughts...', "It's possible to suffer a dulling of the senses...", "Not hearing other vehicles is a problem...', and "I was revving the engine in time to the beat." Slower, more ambient {{U}}tracks{{/U}} like Chopin stimulate a change in a person's brain pattern, encouraging Alpha waves and inducing a feeling of well-being. A state of relaxation might be good for us at most other times, but not at the wheel of the car. Psychologist Professor Shirley Fisher warned. "The greatest danger is fatigue at the wheel. Some music can lull you into concentration loss, or even mini-sleep, which can cause horrific accidents. " "It's a matter of selecting your music to suit the conditions. Stimulating music can be useful on long, boring roads but when traffic conditions are difficult, or traffic is heavy, it can distract you. " There is, however, an up side, as AA psychologist Dr. Robert West pointed out: "if some music affects our ability to drive safely, then the {{U}}reverse{{/U}} is also true. Carefully selected tracks may improve our driving, particularly in the high risk groups. For example, if we could get young male drivers to listen to Mantovani, they would probably slow down. Sadly, I don't think I could persuade many of them to listen, though. " As well as the type of music affecting road safety, the very fact that we have high-tech music systems built into our cars also causes accidents. A recent traffic and road safety report showed that almost forty percent of minor road accidents were caused by people taking their eyes off the road to change a cassette or disc! Whatever our taste in music, or driving style, it looks as if safe driving habits are forced on us in the future. Rover, British Aerospace, Philips and Sweden's Road and Traffic Research Institute have combined to produce a car intelligence system that they have named ARIADN (Application of Real-Time Intelligent Aid for Driving., a sophisticated electronic combined navigation-carphone-collision avoidance system that takes advantage of radar to warn the driver when a collision is possible. If the car ceases to be at a safe braking distance from the one in front, ARIADN sends a vibration through the accelerator pedal to warn the driver to slow down. The vibration becomes more and more severe the closer the car gets to the vehicle in front until, if the warnings go unheeded, the engine cuts out and the hazard warning lights go on. So remember, if music is the food of love, do it slowly, especially if you're driving, then we can all "play" on.

HISTORY OF LANGUAGE 1 In evolutionary history, the development of language set humans apart from the rest of the animal kingdom. Spoken language originated when early humans began to string grunts and squeals together to form a sound-meaning system. Language provided humans with the tools to create ideas and then to communicate these ideas to other people. 2 As human knowledge and civilization expanded, a system that stored information became necessary. The first writing systems used pictures to represent objects. These early systems were successful in recording concrete details concerning trade and taxes, but they could not convey abstract ideas and emotions. Between 800 and 500 B.C., the ancient Greeks began to use a phonetic alphabet that used symbols to represent sounds, with each sound making up part of a word. Thus, written language became a means of mass communication. 3 The expansion of humanity from an oral society to one that also used the written word for communication was a defining point in human civilization. Early oral cultures required a tribal mentality with histories defined by family or clan perspectives, but writing allowed a broader, global perspective to emerge.

Zebra Mollusks ? Small, freshwater zebra mollusks have been invading America"s freshwater lakes and rivers for more than fifteen years. The shellfish are native to Russia, the Balkans, and Poland and were originally found in the areas of the Ural River and the Black, Caspian, and Azov Seas in the 1700s. By the late 1700s and early 1800s, they had spread to many parts of Europe because of the numerous canals. In 1824 these mussels were discovered in Great Britain. Today, they have infested most of Western Europe as well as the Scandinavian countries, Ireland and Italy. Zebra mollusks were transported to North America in 1988 in the ballast water of a transatlantic freighter and were discharged into Lake St. Clair, an inland lake in Michigan which connects Lake Erie and Lake Huron. Within four years the mollusks had infested one lake. Within ten years, more than one hundred lakes had become home for these invaders. Today, these invasive mussels have established themselves in all of the Great Lakes, other inland lakes in Michigan, and the basins of most navigable rivers in the eastern United States including the Mississippi, Tennessee, Ohio, and Hudson Rivers. Their presence has also recently been detected in the Missouri River basin. ? Zebra mollusks, which get their name from the striped pattern of their shells, are prolific breeders. Females can produce between 30,000 and one million eggs each year. During their planktonic larval stage, young zebra mollusks are the size of a human hair and appear invisible to the human eye and the tiny shellfish can live and feed in many different aquatic habitats, and they can move easily and swiftly in water currents and can drift many miles before settling. Adult zebra mollusks live about five years and can survive in fresh water at levels deeper than twenty feet. Once the mollusks reach their adult stage they attach themselves to hard objects in water. Boats, buoys, piers, and fishing gear can be their victims as well as clams, crayfish, turtles and other creatures living in the water. Zebra mollusks also attach themselves to each other to form huge colonies. ? Environmentally, zebra mollusks can be a threat. When they attach themselves to watercraft, the mollusks can cling to the hull or motor or any part of the boat which is immersed in the water. As a result, boats can overheat, have increased drag, and show damaged engine cooling systems. Piers, navigational buoys, and other structures can sink under the weight of the attached mollusks or suffer deterioration and long term damage from the attachment of the shellfish. Many municipalities have been required to redesign the intake systems for their city water supplies because mollusks have clogged the intake pipelines. Other communities have resorted to chemicals to treat and prevent zebra mollusk problems. The mollusks can threaten native wildlife and marine life and upset ecosystems. Marine life is also severely affected by zebra mollusks when the mollusks attach themselves to slow moving animals such as turtles and crayfish or to clams and mussels which are found naturally in fresh water lakes. When the zebra mollusks attach themselves to an object in large numbers, the mollusks are said to be "colonizing." Colonizing interferes with the object"s ability to feed itself and its growth, movement, respiration, and reproduction abilities. [■] Despite problems caused by the mollusks, they also provide benefits to polluted bodies of water. [■] As they filter water, they digest animals and algae that provide food for other fish and animals. [■] The benefit of the filtering process, however, is that water clarity in infested lakes and rivers increases dramatically. These tiny shellfish also provide food for many native birds and fish but they cannot be eaten in amounts great enough to control the mollusk population. [■] Zebra mollusks help provide more healthy environments for aquatic plants, and in some inland lakes and rivers the smallmouth bass population has increased because the additional aquatic plants have provided feeding and nursery areas for young fish. ? Environmental agencies, local communities, and inland lake associations are working diligently to protect people and waters from the threat of the zebra mollusks. Once the mollusks become established in bodies of water, eradication is difficult, if not impossible, because the creatures seem to be oblivious to all but the harshest chemicals—chemicals which can kill other plant and wild life. Because zebra mollusks can survive out of the water for as long as five days in cool, humid climates, boaters, fishing enthusiasts, and all lake lovers need to learn how not to transmit the invaders, in larvae and adult form, between bodies of water. Glossary freighter: a large ship or airplane that is designed for carrying freight breeder: people who breed animals or plants buoy: a floating object that is used to show ships and boats where they can go and to warn them of danger

Directions: Read the passage. Then answer the questions. Give yourself 20 minutes to complete this practice set. THE CAMBRIAN EXPLOSION The geologic timescale is marked by significant geologic and biological events, including the origin of Earth about 4.6 billion years ago, the origin of life about 3.5 billion years ago, the origin of eukaryotic life-forms (living things that have cells with true nuclei) about 1.5 billion years ago, and the origin of animals about 0.6 billion years ago. The last event marks the beginning of the Cambrian period. Animals originated relatively late in the history of Earth—in only the last 10 percent of Earth's history. During a geologically brief 100-million-year period, all modern animal groups (along with other animals that are now extinct) evolved. This rapid origin and diversification of animals is often referred to as "the Cambrian explosion." Scientists have asked important questions about this explosion for more than a century. Why did it occur so late in the history of Earth? The origin of multicellular forms of life seems a relatively simple step compared to the origin of life itself. Why does the fossil record not document the series of evolutionary changes during the evolution of animals? Why did animal life evolve so quickly? Paleontologists continue to search the fossil record for answers to these questions. One interpretation regarding the absence of fossils during this important 100-million-year period is that early animals were soft bodied and simply did not fossilize. Fossilization of soft-bodied animals is less likely than fossilization of hard-bodied animals, but it does occur. Conditions that promote fossilization of soft-bodied animals include very rapid covering by sediments that create an environment that discourages decomposition. In fact, fossil beds containing soft-bodied animals have been known for many years. The Ediacara fossil formation, which contains the oldest known animal fossils, consists exclusively of soft-bodied forms. Although named after a site in Australia, the Ediacara formation is worldwide in distribution and dates to Precambrian times. This 700-million-year-old formation gives few clues to the origins of modern animals, however, because paleontologists believe it represents an evolutionary experiment that failed. It contains no ancestors of modern animal groups. A slightly younger fossil formation containing animal remains is the Tommotian formation, named after a locale in Russia. It dates to the very early Cambrian period, and it also contains only soft-bodied forms. At one time, the animals present in these fossil beds were assigned to various modern animal groups, but most paleontologists now agree that all Tommotian fossils represent unique body forms that arose in the early Cambrian period and disappeared before the end of the period, leaving no descendants in modern animal groups. A third fossil formation containing both soft-bodied and hard-bodied animals provides evidence of the result of the Cambrian explosion. This fossil formation, called the Burgess Shale, is in Yoho National Park in the Canadian Rocky Mountains of British Columbia. Shortly after the Cambrian explosion, mud slides rapidly buried thousands of marine animals under conditions that favored fossilization. These fossil beds provide evidence of about 32 modern animal groups, plus about 20 other animal body forms that are so different from any modern animals that they cannot be assigned to any one of the modern groups. These unassignable animals include a large swimming predator called Anomalocaris and a soft-bodied animal called Wiwaxia, which ate detritus or algae. The Burgess Shale formation also has fossils of many extinct representatives of modern animal groups. For example, a well-known Burgess Shale animal called Sidneyia is a representative of a previously unknown group of arthropods (a category of animals that includes insects, spiders, mites, and crabs). Fossil formations like the Burgess Shale show that evolution cannot always be thought of as a slow progression. The Cambrian explosion involved rapid evolutionary diversification, followed by the extinction of many unique animals. Why was this evolution so rapid? No one really knows. Many zoologists believe that it was because so many ecological niches were available with virtually no competition from existing species. Will zoologists ever know the evolutionary sequences in the Cambrian explosion? Perhaps another ancient fossil bed of soft-bodied animals from 600-million-year-old seas is awaiting discovery.

Reading4"FourStagesofPlanetaryDevelopment"PlanetaryDevelopment→InourstudyoftheplanetEarth,wewillfindafour-stagehistoryofplanetarydevelopment.Themoonandalltheterrestrialplanetshavepassedthroughthesestages,althoughdifferencesinthewaytheplanetswerealteredbythesestageshaveproduceddramaticallydifferentworlds.Themoon,forexample,ismuchlikeEarth,butitsevolutionhasbeendramaticallyalteredbyitssmallersize.Asweexplorethesolarsystem,wewilldiscovernotentirelynewprocessesbutratherfamiliareffectsworkinginslightlydifferentways.TheFourStagesThefirststageofplanetaryevolutionisdifferentiation,theseparationofmaterialaccordingtodensity.Earthnowhasadensecoreandalower-densitycrust,andthatstructuremusthaveoriginatedveryearly.DifferentiationwouldhaveoccurredeasilyifEarthweremoltenwhenitwasyoung.TwosourcesofheatcouldhaveheatedEarth.First,heatofformationwouldbecreatedbyin-fallingmaterial.AmeteoritehittingEarthathighvelocityconvertsmostofitsenergyofmotionintoheat,andthein-fallingofalargenumberofmeteoritescouldreleasetremendousheat.IfEarthformedrapidly,thisheatwouldhaveaccumulatedmuchmorerapidlythanitcouldleakaway,andEarthmayhavebeenmoltenwhenitformed.Asecondsourceofheatrequiresmoretimetodevelop.ThedecayofradioactiveelementstrappedintheEarthreleasesheatgradually;but,assoonasEarthformed,thatheatwouldhavebeguntoaccumulateandcouldhavehelpedmeltEarthtofacilitatedifferentiation.MostofEarth'sradioactiveelementsarenowconcentratedinthecrust,wheretheycontinuetowarmandsoftentherocklayers.Earthformedbymaterialfallingtogether,butmeteoritescouldhaveleftnotraceuntilacrustsolidified.OnceEarthhadahardsurface,themeteoritescouldformcraters.Thissecondstageinplanetaryevolution,cratering,wasviolent.Theheavybombardmentwasintensebecausethesolarnebulawasfilledwithrockyandicydebris,andtheyoungEarthwasbatteredbymeteoritesthatpulverizedthenewlyformingcrust.Thelargestmeteoritesblastedoutcraterbasinshundredsofkilometersindiameter.Asthesolarnebulacleared,theamountofdebrisdecreased,andthelevelofcrateringfelltoitspresentlowlevel.AlthoughmeteoritesstilloccasionallystrikeEarthanddigcraters,crateringisnolongerthedominantinfluenceonEarth'sgeology.AswecompareotherworldswithEarth,wewilldiscovertracesofthisintenseperiodofcratering,theheavybombardment,oneveryoldsurfaceinthesolarsystem.→Thethirdstage,flooding,nodoubtbeganwhilecrateringwasstillintense.Thefracturingofthecrustandtheheatingcausedbyradioactivedecayallowedmoltenrockjustbelowthecrusttowellupthroughfissuresandfloodthedeeperbasins.Wewilldiscusssuchfloodedbasinsonotherworlds,suchasthemoon,butalltracesofthisearlylavafloodinghavebeendestroyedbylatergeologicalactivityinEarth'scrust.OnEarth,floodingcontinuedastheatmospherecooledandwaterfellasrain,fillingthedeepestbasinstoproducethefirstoceans.NoticethatonEarthfloodinginvolvesbothlavaandwater,acircumstancethatwewillnotfindonmostworlds.Thefourthstage,slowsurfaceevolution,hascontinuedforthelast3.5billionyearsormore.Earth'ssurfaceisconstantlychangingassectionsofcrustslideovereachother,pushupmountains,andshiftcontinents.AlmostalltracesofthefirstbillionyearsofEarth'sgeologyhavebeendestroyedbytheactivecrustanderosion.EarthasaPlanetAllterrestrialplanetspassthroughthesefourstages,sointhatrespect,Earthisagoodbasicreferenceplanetforcomparativeplanetology.Someplanetshaveemphasizedonestageoveranother,andsomeplanetshavefailedtoprogressfullythroughthefourstages.Nevertheless,Earthisagoodstandardofcomparison.EverymajorprocessonanyrockyworldinoursolarsystemisrepresentedinsomeformonEarth.Ontheotherhand,Earthispeculiarintwoways.First,ithaslargeamountsofliquidwateronitssurface.Fully75percentofitssurfaceiscoveredbythisliquidandnootherplanetinoursolarsystemisknowntohavesuchextensiveliquidwateronitssurface.Furthermore,someofthematteronthesurfaceofthisworldisalive,andasmallpartofthatlivingmatterisaware.WedonotknowhowthepresenceoflivingmatterhasaffectedtheevolutionofEarth,butthisprocessseemstobetotallymissingfromotherworldsinoursolarsystem.Glossarymeteorite:amassthatfallstothesurfaceofaplanetfromspaceplanetology:thestudyofplanets

Whydoesthestudentcometotheprofessor'soffice?

TOEFLReadingPassage2TheMediterranean'sKillerAlgae1.Todaytherearemanyinvasivespeciesthreateningecosystemsallovertheworld,butfewareofasmuchconcernasCaulerpataxifolia.Thisspeciesofgreenalgaegrowsinlong,thinbladessimilarinappearancetoseagrass.Eachindividualalgaissingle-celled,withalengthofuptoameter,theyaresomeofthelargestcellsintheworld.Algaecontainchlorophyllandproducetheirownfoodthroughphotosynthesis.Alsotheyreproduceasexually,meaningthatifanalgaiscutintwoeachhalfwiltdevelopintoawholeneworganism.2.Caulerpataxifolia'snativehabitatsarethetropicalwatersoftheCaribbean,southPacific,eastAtlantic,andIndianOcean.However,inthe1970s,anewstrainwasbredinEuropetodecorateexhibitsinsaltwateraquariums.Thestrainprovedusefulforthispurpose,foritwasabletogrowmorequickly,formdenserpatches,andtolerateagreatertemperaturerange--from10to31degreeCelsius--thantheoriginal.CreatedinGermany,theimprovedalgalstrainwasdistributedin1980to,amongotherfacilities,theOceanographicMuseuminMonaco,atinycountryontheFrenchcoast.Fouryearslater,asampleofthealgaeescapedthemuseumandbegantogrowontheseafloorjustoutside.3.By1989,thissmallsamplehadturnedintoa2.2-acrefieldofCaulerpataxifolia.ItcontinuedtospreadrapidlythroughouttheMediterranean,appearingatlocationsupto350kilometersfromMonacoin1991,andby1994ithadarrivedinthewatersofItaly,Croatia,andSpain.Officialsintheregion,however,wereslowtorespond,TheirdelaysallowedthespeciestodevelopastrongfootholdintheMediterranean,andtheinvasionreachedglobalproportionswhenthealgaewerespottedoffthecoastsofCaliforniain1998andAustraliain2000.4.Dubbed"killeralgae"bymanyscientists,theaquariumstrainofCaulerpataxifoliaposesawholehostofthreatstotheareasitcolonizes.Itsrapid,densegrowthpatternsenableittosuccessfullyout-competeallnativevarietiesofalgaeandseagrasses.Duetoitsabilitytothriveinbothwarmandcoldwatersatavarietyofdepths(anywherefromoneto100meters),fewcoastalmarineenvironmentsaresafe.Thedisappearanceofnativevegetationaffectsalltheanimalsthatdependonitforfoodandshelter,whileCaulerpataxifoliaitselfisinedibletomostspeciesbecauseitsecretesmanyharmfultoxins.5.Thealgaealsocausenegativerepercussionsforhumans,inparticularthecommercialfishingindustry.Asaresultofhabitatloss,manyspeciesfishermenhavereliedonforcenturiesarenolongeravailable,andthealgaearenotoriousforcloggingfishingnetsandevensnaggingboatpropellers.Inaddition,thedecreaseinthenaturaldiversityofplantandanimallifeintheMediterraneanhasledtoaseveredeclineinmarinetourism.6.Inrecentyears,manymethodshavebeenemployedinattemptstoeliminatetheinvasivealgae.Thesimplestisknownasmanualuprooting,inwhichindividualdiversusetheirhandstopullthealgaeoutbytheroots.Unfortunately,CaulerpataxifoliahasspreadintheMediterraneantothepointthatthismethodisnolongerfeasiblethere.Whileitholdspromiseforremovingsmall,isolatedpatches,extremecaremustbetaken,asanysmallfragmentsofthealgaeleftbehindcouldgrowandtakerootonceagain.7.Variousphysico-chemicalprocedureshavebeentriedaswell.Theseincludeexposuretocopperandsalt,airsuction,ultrasounddevices,andhotwaterjets,buteachseemsmoreeffectiveatslowingthealgae'sexpansionthanactuallyeliminatingit.Studiesofbiologicalmethods,suchastheintroductionofseaslugs*thatfeedonthealgae,havealsoyieldeddiscouragingresults.Insteadofconsumingthealgaeblades,theslugsmerelycutthemintosmallpiecesthatcouldeasilydisperseandformnewcolonieselsewhere.Untilananswertotheproblemisfound,scientistsurgecaution,encouragingmarineorganizationstobeonthelookoutfornewalgaegrowthandtohelpeducatethepublicabouttheseriousrisksthisinvasivespeciesrepresents.slug*asmallslow-movingcreaturewithalongsoftbodyandnolegs,likeasnailwithoutashell.

Whatdoestheprofessormainlydiscussinthelecture?A.Howfossilsarediscoveredandexamined.B.Theimportanceandpreservationoffossils.C.Howfossilsarestudiedandinvestigated.D.Howfossilsareusedtolocateoilandotherresources.

THE SENSE OF SMELL 1 Olfaction—smell—is the most direct of all the senses. Whereas signals from the other senses are first sent to the brain"s thalamus , smells are sent right into the brain"s interpretive regions for instant processing. Smell is thought to be the oldest sense in terms of human evolution, which may explain why it is hard-wired into the brain. The olfactory nerve, which manages the perception of smells, is essentially an extension of the brain because it provides a direct link from receptors at the top of the nose to the portion of the brain that controls memory, emotion, and behavior. 2 The olfactory system detects certain airborne chemicals that enter the nose and then transmits this chemical information to the limbic system in the brain. The olfactory region at the upper end of each nostril is yellow, moist, and full of fatty substances. The shade of yellow indicates the strength of the sense of smell: the deeper the shade, the keener and more acute it is. Animals have a very strong sense of smell, so their olfactory regions are dark yellow to reddish brown, while those of humans are light yellow. 3 When an odorous substance enters the nose, it binds to olfactory receptor cells, the neurons lining the yellow upper portion of the nasal cavity. Olfactory receptor cells contain microscopic hairs called cilia that extend into the layer of mucus coating the inside of the nose. Odor molecules diffuse into this region and are absorbed by the cilia of the olfactory receptor cells. What this means is that when we hold a rose to our nose and inhale, odor molecules float up into the nasal cavity, where they are absorbed by five million olfactory receptor cells. The receptor cells alert the olfactory nerve, which sends impulses to the brain"s olfactory bulb, or smell center. Thus, olfactory information about the rose enters the brain"s limbic system, where, in most of us, it stimulates a feeling of pleasure. 4 The limbic system of the brain integrates memory, emotion, and behavior. The system is composed of a group of related nervous system structures that are the functional center of emotions such as anger, fear, pleasure, and sadness. The components of the limbic system are linked to the cerebral cortex, the part of the brain involved in complex learning, reasoning, and personality. The cerebral cortex makes decisions about the emotional content of these unique human qualities after "consulting" the limbic system and other brain centers in processing and retrieving memories. It may, in turn, use memories to modify behavior. 5. Scent may be the strongest trigger of memory and emotions. When we inhale a scent, receptors in the brain"s limbic center compare the odor entering our nose to odors stored in our memory. Along the way, memories associated with those odors are stimulated. A smell can be overwhelmingly nostalgic, evoking powerful images and emotions of past situations. The waxy fragrance of crayons can instantly transport us to our second-grade classroom, or the scent of freshly mown grass can flood us with the joy of summer freedom. What we see and hear may fade quickly in short-term memory, but what we smell is sent directly to long-term memory. Numerous studies have shown that smell memory is long and resilient, and the earliest odor associations we make often remain with us. In one study of older adults, researchers found that word and visual cues elicited memories from the subjects" adolescence and young adulthood, but smell cues evoked thoughts of early childhood. The subjects were able to describe the smell memories in rich and emotional terms, and they were more likely to report the sudden feeling of being back in time. 6 Smells can increase alertness and stimulate learning and retention. In one study, children memorized a word list, which was presented both with and without accompanying scents. The children recalled words on the list more easily and with higher accuracy when the list was given with scents than without, showing the link between smell and the ability to retain information. In another study, researchers examined how various smells can increase alertness and decrease stress. They found that the scent of lavender could wake up the metabolism and make people more alert. They also found that the smell of spiced apples could reduce blood pressure and avert a panic attack in people under stress. Glossary: thalamus: part of the brain that relays sensory impulses to the cerebral cortex, which controls higher functions such as thinking and learning

Directions: Read the passage. Then answer the questions. Give yourself 20 minutes to complete this practice set. METHODS OF STUDYING INFANT PERCEPTION In the study of perceptual abilities of infants, a number of techniques are used to determine infants" responses to various stimuli. Because they cannot verbalize or fill out questionnaires, indirect techniques of naturalistic observation are used as the primary means of determining what infants can see, hear, feel, and so forth. Each of these methods compares an infant"s state prior to the introduction of a stimulus with its state during or immediately following the stimulus. The difference between the two measures provides the researcher with an indication of the level and duration of the response to the stimulus. For example, if a uniformly moving pattern of some sort is passed across the visual field of a neonate (newborn), repetitive following movements of the eye occur. The occurrence of these eye movements provides evidence that the moving pattern is perceived at some level by the newborn. Similarly, changes in the infant"s general level of motor activity—turning the head, blinking the eyes, crying, and so forth—have been used by researchers as visual indicators of the infant"s perceptual abilities. Such techniques, however, have limitations. First, the observation may be unreliable in that two or more observers may not agree that the particular response occurred, or to what degree it occurred. Second, responses are difficult to quantify. Often the rapid and diffuse movements of the infant make it difficult to get an accurate record of the number of responses. The third, and most potent, limitation is that it is not possible to be certain that the infant"s response was due to the stimulus presented or to a change from no stimulus to a stimulus. The infant may be responding to aspects of the stimulus different than those identified by the investigator. Therefore, when observational assessment is used as a technique for studying infant perceptual abilities, care must be taken not to overgeneralize from the data or to rely on one or two studies as conclusive evidence of a particular perceptual ability of the infant. Observational assessment techniques have become much more sophisticated, reducing the limitations just presented. Film analysis of the infant"s responses, heart and respiration rate monitors, and nonnutritive sucking devices are used as effective tools in understanding infant perception. Film analysis permits researchers to carefully study the infant"s responses over and over and in slow motion. Precise measurements can be made of the length and frequency of the infant"s attention between two stimuli. Heart and respiration monitors provide the investigator with the number of heartbeats or breaths taken when a new stimulus is presented. Numerical increases are used as quantifiable indicators of heightened interest in the new stimulus. Increases in nonnutritive sucking were first used as an assessment measure by researchers in 1969. They devised an apparatus that connected a baby"s pacifier" to a counting device. As stimuli were presented, changes in the infant"s sucking behavior were recorded. Increases in the number of sucks were used as an indicator of the infant"s attention to or preference for a given visual display. Two additional techniques of studying infant perception have come into vogue. The first is the habituation-dishabituation technique, in which a single stimulus is presented repeatedly to the infant until there is a measurable decline (habituation) in whatever attending behavior is being observed. At that point a new stimulus is presented, and any recovery (dishabituation) in responsiveness is recorded. If the infant fails to dishabituate and continues to show habituation with the new stimulus, it is assumed that the baby is unable to perceive the new stimulus as different. The habituation-dishabituation paradigm has been used most extensively with studies of auditory and olfactory perception in infants. The second technique relies on evoked potentials, which are electrical brain responses that may be related to a particular stimulus because of where they originate. Changes in the electrical pattern of the brain indicate that the stimulus is getting through to the infant"s central nervous system and eliciting some form of response. Each of the preceding techniques provides the researcher with evidence that the infant can detect or discriminate between stimuli. With these sophisticated observational assessment and electro physiological measures, we know that the neonate of only a few days is far more perceptive than previously suspected. However, these measures are only "indirect" indicators of the infant"s perceptual abilities. pacifier1 : a small plastic device for babies to suck or bite on

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