MHE_Rdg_Wonders_LvRdr_G5_On-Level_U6W3_28.pdf

Program:CR 14Component:LRG5U6W3 OPDFVendor:Learning MediaLevel:50Expository Text PAIREDREADWhy Bat Flies at Nightby Jocelyn CranefieldCV_CR14_LR_G5_U6W3L50_O_118569.indd 3CV_CR14_LR_G5_U6W3L50_O_118569.indd 314/03/12 12:15 PM14/03/12 12:15 PMSTRATEGIES&SKILLSComprehensionStrategy:Ask and Answer QuestionsSkill:Cause and EffectVocabulary StrategyParagraph CluesVocabulary adaptations,agile,caches,dormant,forage,frigid,hibernate,insulateContent StandardsScienceLife Science Photography Credit:Mark Moffett/Minden Pictures/Getty images.*The total word count is based on words in the running text and headings only.Numerals and words in captions,labels,diagrams,charts,and sidebars are not included.Word Count:1,723*AProgram:CR 14Component:LRG5U6W3 OPDFVendor:Learning MediaLevel:50Copyright The McGraw-Hill Companies,Inc.All rights reserved.No part of this publication may be reproduced or distributed in any form or by any means,or stored in a database or retrieval system,without the prior written consent of The McGraw-Hill Companies,Inc.,including,but not limited to,network storage or transmission,or broadcast for distance learning.Send all inquiries to:McGraw-Hill EducationTwo Penn PlazaNew York,New York 10121ISBN:978-0-02-118569-6MHID:0-02-118569-7Printed in the United States.1 2 3 4 5 6 7 8 9 DOC 15 14 13 12 11 10IFCIBC_CR14_LR_G5_U6W3L50_O_118569.indd 2IFCIBC_CR14_LR_G5_U6W3L50_O_118569.indd 214/03/12 12:15 PM14/03/12 12:15 PMPAIREDREADby Jocelyn Cranefield Essential QuestionHow are living things adapted to their environment?Program:CR 14Component:LRG5U6W3-OPDFVendor:Learning MediaLevel:50Introduction .2Chapter 1From the Entrance to the Twilight Zone .4Chapter 2Dark and Surprising Places .10Conclusion.16Respond to Reading.18Why Bat Flies at Night .19Glossary.22Index.23Focus on Science .24001-009_CR14_LR_G5_U6W3L50_O_118569.indd 1001-009_CR14_LR_G5_U6W3L50_O_118569.indd 115/03/12 12:26 PM15/03/12 12:26 PMCaves are found all over the world.They often extend far beyond their entrances and go deep beneath Earths surface.At first,a cave might seem to be just a dark,empty space.If you shine your flashlight inside the cave,youll probably just see emptiness.However,chances are that if you go inside,you wont be alone.Caves can be on the coast,in the forest,or under the desert.Some are made out of limestone and others out of marble or lava.Some caves are full of beautiful stone formations,and others are full of smelly,poisonous gases.However,the worlds caves all have one thing in commontheyre a haven for animals.Lechuguilla Cave in New Mexico is famous for its beautiful mineral formations.Introduction2Program:CR 14Component:LRG5U6W3 OPDFVendor:Learning MediaLevel:502MICHAEL NICHOLS/National Geographic Stock001-009_CR14_LR_G5_U6W3L50_O_118569.indd 2001-009_CR14_LR_G5_U6W3L50_O_118569.indd 215/03/12 12:26 PM15/03/12 12:26 PMCAVE DEPTHKrubera Cave,7,188 feet deepBUILDING HEIGHT1,000 ft1,000 ft2,000 ft2,723 ft0 ft2,000 ft3,000 ft4,000 ft5,000 ft6,000 ft7,000 ftCAVE LOCATIONSSome of these animals are visitors to the cave,while others are permanent residents.Many of these creatures have adaptations to help them live in a cave environment.Adaptations are special features that help a living thing survive in particular conditions.The Krubera Cave CAVES OF ALL SIZES Explorers have discovered more than 50,000 natural caves in the world.Some caves are single tunnels,but others are systems of connected underground spaces.The deepest known cave is the Krubera Cave,near the Black Sea.It is at least 7,188 feet deep.Compare its depth with the heights of some tall buildings,below.The worlds longest cave is Kentuckys Mammoth Cave.This limestone labyrinth runs for more than 350 miles underground.3Program:CR 14Component:LRG5U6W3 OPDFVendor:Learning MediaLevel:503001-009_CR14_LR_G5_U6W3L50_O_118569.indd 3001-009_CR14_LR_G5_U6W3L50_O_118569.indd 315/03/12 12:26 PM15/03/12 12:26 PMSome animals,such as bats,skunks,raccoons,and snakes,visit caves for shelter or to sleep.They stay near the cave entrance,where it can be warm in winter and cool in summer.These animals are called trogloxenes,or cave visitors.Trogloxenes spend just part of their lives in caves.They cant survive without going outside to get food.The Mexican free-tailed bat is a trogloxene.It is nocturnal and roosts in colonies hanging from cave roofs during the day.At dusk it flies out of the cave to catch and eat insects.As the sun sets,these bats emerge from their cave to hunt.From the Entrance to the Twilight ZoneChapter ONE 4Program:CR 14Component:LRG5U6W3 OPDFVendor:Learning MediaLevel:504Fred Bruemmer/Photolibrary/Getty Images001-009_CR14_LR_G5_U6W3L50_O_118569.indd 4001-009_CR14_LR_G5_U6W3L50_O_118569.indd 415/03/12 12:26 PM15/03/12 12:26 PMLike most bats,the Mexican free-tailed bat has an adaptation called echolocation to help it find its way in the dark cave.The bat makes high-pitched squeaking sounds,then listens for an echo.It uses the echo to figure out where things are.In some places,bats hibernate in caves during the winter.However,they dont spend the whole winter asleep.They usually wake up from their dormant state around every 15 to 30 days for short periods.A place where a bat hibernates is called a hibernaculum.In cold climates,bears sometimes spend the winter in caves,too.The air inside the cave is warmer than the air outside,helping to insulate animals from the cold.The endangered Virginia big-eared bat hibernates in caverns in West Virginia.Bears enter a deep sleep in winter that some scientists consider to be a type of hibernation.5Program:CR 14Component:LRG5U6W3 OPDFVendor:Learning MediaLevel:505(t)AFP/Getty Images/Newscom,(b)Juniors Bildarchiv/Alamy001-009_CR14_LR_G5_U6W3L50_O_118569.indd 5001-009_CR14_LR_G5_U6W3L50_O_118569.indd 515/03/12 12:26 PM15/03/12 12:26 PMFarther into the cave is the cool,damp twilight zone.There is very little light here,so green plants cant grow.Many of the creatures that live here are troglophiles,or cave lovers.They can spend their whole lives in caves,but they can also survive outside.Troglophiles include certain types of spiders,earthworms,beetles,frogs,and crickets.Food in the twilight zone is scarce.The animals living here cant rely on their sight alone to survive.They use other senses,such as hearing or touch,to help them locate food and find their way around.Their adaptations help them to live in these conditions.The glowworm,the larva of an insect called a fungus gnat,is also a troglophile.Its adaptation is the ability to light up its abdomen to attract prey.First the glowworm spins a web out of sticky droplets,then it switches on its light.The glowworm caches its insect victims in the web until it needs a meal.If the glowworm hears a noise,it can turn off its light.6Program:CR 14Component:LRG5U6W3 OPDFVendor:Learning MediaLevel:506blickwinkel/Alamy001-009_CR14_LR_G5_U6W3L50_O_118569.indd 6001-009_CR14_LR_G5_U6W3L50_O_118569.indd 615/03/12 12:26 PM15/03/12 12:26 PMThe New Zealand cave weta,a cricket,lives in colonies on the undersides of cave roofs.It has extra-long antennaeup to seven times longer than its body.These antennae help it to navigate and to feel around for food.With its tiny body and long legs,this agile insect can leap more than 6 feet!ADAPTING TO SILENCEIn a place where food is scarce,its useful to keep quiet!Instead of chirping,the African cave cricket communicates secretly.It uses its wings to send out tiny doughnut-shaped puffs of air called vortices.Other cave crickets can feel these vortices,but predators cant.The New Zealand cave wetas long legs help it to leap quickly out of harms way.7Program:CR 14Component:LRG5U6W3 OPDFVendor:Learning MediaLevel:507(t)Natural Visions/Alamy,(b)Premaphotos/Alamy001-009_CR14_LR_G5_U6W3L50_O_118569.indd 7001-009_CR14_LR_G5_U6W3L50_O_118569.indd 715/03/12 12:26 PM15/03/12 12:26 PMWhat do animals eat in a cave?Plants cant grow in the dark,but plant-based nutrients are brought into caves in different ways.Rain and underground streams wash in twigs,leaves,and seeds,along with insects.The droppings of animals such as bats and cave crickets include recycled plant material.These are important sources of food for permanent cave dwellers.Molds,fungi,and bacteria break down all this organic material and make it suitable for microscopic animals to eat.These microscopic animals are eaten by larger cave dwellers.The larger animals are then eaten by other cave predators.CAVE LIONSBased on the ages of bones they have found,scientists believe that the European cave lion lived between 12,000 and 40,000 years ago.It was about 25 percent larger than todays lions.Scientists think that it probably didnt live in caves most of the time.It is called the cave lion because the bones of these animals were found in caves.Underground conditions are usually stable.Skeletons of animals that die in caves can be preserved for a long time.Scientists have been able to learn about these big cats from their very old bones.8Program:CR 14Component:LRG5U6W3 OPDFVendor:Learning MediaLevel:508CLAY BRYCE/AFP/Newscom001-009_CR14_LR_G5_U6W3L50_O_118569.indd 8001-009_CR14_LR_G5_U6W3L50_O_118569.indd 815/03/12 12:26 PM15/03/12 12:26 PMSmall insects such as mosquitoes,gnats,glowworms,cricketsSpidersCentipedes BeetlesFrogsSporesBacteriaThe nutrients in guano,or bat droppings,and other materials are broken down and recycled by some cave creatures and microscopic organisms.These creatures are eaten by larger predators.CAVE FOOD WEBGuanoEarthwormsBatsTiny insects,mitesCave siltMatter carried by waterMineralsFungiMold 9Program:CR 14Component:LRG5U6W3 OPDFVendor:Learning MediaLevel:509001-009_CR14_LR_G5_U6W3L50_O_118569.indd 9001-009_CR14_LR_G5_U6W3L50_O_118569.indd 915/03/12 12:26 PM15/03/12 12:26 PMImagine if you were transported deep underground into the heart of a cavethe dark zone.Here there is no light or wind,and no plants grow.What would it take to live here?Life in the Dark ZoneAnimals that live permanently in this dark zone are called troglobites,or cave dwellers.They have adaptations,such as small bodies,long limbs,and lengthy antennae.Other adaptations are less obvious,such as the ability to detect small vibrations or smells.Their adaptations help these creatures to move,forage,and feed efficiently in a pitch-black environment where food is scarce.This eyeless,wingless insect called a dipluran has long antennae and two tails.Dark and Surprising PlacesChapter TWO 10Program:CR 14Component:LRG5U6W3-OPDFVendor:Learning MediaLevel:50Dante Fenolio/Photo Researchers/Getty Images(t)TomHartman/OxfordScientific/GettyImages(b)DanteFenolio/PhotoResearchers Inc010-018_CR14_LR_G5_U6W3L50_O_118569.indd 10010-018_CR14_LR_G5_U6W3L50_O_118569.indd 1015/03/12 12:30 PM15/03/12 12:30 PMMany troglobites do not have the same adaptations that animals above ground need to survive.If you live your whole life in the dark,eyes are not very useful.Animals living in the dark zone typically have tiny eyes or none at all.In the outside world,most animals have coloring in their skin called pigment.Pigment is an adaptation that protects animals from the sun or provides them with camouflage.However,pigment is of no use in the dark zone of a cave.Some animals here have skin that is nearly see-through.Animals with these adaptations are well suited to deep-cave life.However,they could not survive for long in the world outside.This cave harvestman has long,thin legs,a tiny body,and is blind.This pseudoscorpion has no eyes,but very long pincers.11Program:CR 14Component:LRG5U6W3-OPDFVendor:Learning MediaLevel:50(t)Tom Hartman/Oxford Scientific/Getty Images,(b)Dante Fenolio/Photo Researchers,Inc.010-018_CR14_LR_G5_U6W3L50_O_118569.indd 11010-018_CR14_LR_G5_U6W3L50_O_118569.indd 1115/03/12 12:30 PM15/03/12 12:30 PMENTRANCE ZONETWILIGHT ZONEDARK ZONETROGLOBITESTROGLOPHILESTROGLOXENESSTYGOBITESSTYGOPHILESSTYGOXENES12Program:CR 14Component:LRG5U6W3-OPDFVendor:Learning MediaLevel:50Illustration:Yasin Karadeniz010-018_CR14_LR_G5_U6W3L50_O_118569.indd 12010-018_CR14_LR_G5_U6W3L50_O_118569.indd 1215/03/12 12:30 PM15/03/12 12:30 PMThe Texas blind salamander has no eyes and hunts by sensing its preys movements in the water.This cave crayfish has no pigment.Aquatic Cave DwellersCreatures that live on land arent the only cave dwellers.Many caves contain networks of underground streams and ponds with specially adapted aquatic animals living in and around them.Aquatic cave dwellers that cant survive outside the cave environment are called stygobites.Stygobites include blind fish,salamanders without eyes,translucent crayfish,and other crustaceans with no pigment.The water that flows through underground caves usually enters from outside the cave,then flows back out again.It transports aquatic creatures into and out of the cave.Stygoxenes are aquatic visitors from outside.Stygophiles are water lovers that may also spend time outside the cave environment.13Program:CR 14Component:LRG5U6W3-OPDFVendor:Learning MediaLevel:50(l)Dante Fenolio/Photo Researchers/Getty Images,(r)Tom Uhlman/Alamy010-018_CR14_LR_G5_U6W3L50_O_118569.indd 13010-018_CR14_LR_G5_U6W3L50_O_118569.indd 1315/03/12 12:30 PM15/03/12 12:30 PMExtreme Cave DwellersCave creatures have been found in unexpected places.In 2001,tiny stygobites that resembled shrimp were discovered in limestone caves under the Western Australian desert.The caves are difficult to access,so scientists stay above ground and use fishing rods and nets to scoop up the tiny animals.Some caves provide even more hostile conditions.These environments are too cold,too hot,or too toxic for most cave creatures to live in.Yet scientists have found specially adapted microscopic forms of life living there.Animals that are adapted to live in extreme conditions are called extremophiles.This scientist is fishing down a borehole for subterranean aquatic animals in the Western Australian arid zone.14Program:CR 14Component:LRG5U6W3-OPDFVendor:Learning MediaLevel:50W F Humphreys,Western Australian Museum010-018_CR14_LR_G5_U6W3L50_O_118569.indd 14010-018_CR14_LR_G5_U6W3L50_O_118569.indd 1415/03/12 12:30 PM15/03/12 12:30 PMMost animals could not survive in the frigid conditions in Greenlands ice caves.But scientists have discovered microscopic creatures living there,too.These creatures are able to withstand the caves sub-zero temperatures.Mexicos Cueva de Villa Luz is another extreme cave environment.The cave emits a toxic gas called hydrogen sulfide.Scientists have given the microbes that live on this poisonous gas names such as snottites,blue goo,and slime balls!Scientists working here carry meters to monitor the level of gas inside the cave.Extremophiles live in Greenlands frozen ice caves.Mexicos Cueva de Villa Luz is home to extremophiles such as these sulfur-eating bacteria.Program:CR 14Component:LRG5U6W3-OPDFVendor:Learning MediaLevel:5015(t)moodboard/Alamy,(b)Stephen Alvarez/National Geographic/Getty Images010-018_CR14_LR_G5_U6W3L50_O_118569.indd 15010-018_CR14