Reading Essentials for Biology Glencoe (794133), страница 87
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This process, calledpreening, keeps the feathers in good condition for flight. When itpreens, a bird also rubs oil from a gland located near the tail ontothe feathers. Water birds must do this in order to waterprooftheir feathers.Bird feathers wear out and are replaced. Birds shed their oldfeathers and grow new ones in a process called molting. Mostbirds molt in late summer. They do not lose all their feathers atonce and can continue to fly while they molt. Wing and tailfeathers are usually lost in pairs. This enables a bird to maintainits balance while flying.READING ESSENTIALS1. Why do birds preen theirfeathers?________________________________________________________________________Chapter 31383NameDateClassSection31.2Birds, continuedHow do birds fly?2.
What two major adaptations were necessary sothat birds could fly?________________________________________________The front limbs of birds have changed into wings. Strong muscles that are used while a bird flies are attached to a large breastbone and to the upper bone of each wing. The breastbone iscalled the sternum. The sternum supports the thrust and powerthat the muscles produce when the wings move to get the birdoff the ground.
Feathers and wings are adaptations that allowbirds to fly.Anteriorair sacs384Chapter 31Birds need high levels of energy to fly. Several factors areinvolved in maintaining these high energy levels. Birds’ fourchambered hearts beat quickly. The rapid heartbeat moves oxygenated blood quickly through the body. The quick movementof blood keeps birds’ cells supplied with the oxygen they needto produce energy.Birds have two breathing cycles. Abird’s respiratory system brings oxygenated air to the lungs both when theKey: Breathing cyclesTracheabird inhales and when it exhales. The resCycle 1Anteriorpiratory system consists of lungs andInhalation 1air sacsExhalation 2anterior, or front, and posterior, or back,LungCycle 2air sacs.
Air follows a one-way path inInhalation 1birds. When a bird inhales in Cycle 1,Exhalation 2oxygenated air passes through its tracheaand into the lungs. The trachea is locatedin the throat portion of the bird. Gasexchange occurs in the lungs. Most of theinhaled air passes directly into the posterior air sacs. When a bird exhales thedeoxygenated air from the lungs, oxyPosteriorgenated air goes into the lungs from theair sacsposterior air sacs. At the next inhalationin Cycle 2, the deoxygenated air in thelungs flows into the anterior air sacs. Then,at the next exhalation, air flows from theanterior air sacs out of the trachea.READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Why do birds need strong circulatory andrespiratory systems?NameDateClassSection31.2Birds, continuedWhat is an endotherm?Birds are endotherms.
An endotherm is an animal that maintains a nearly constant body temperature. It does not depend onthe environment to change its body temperature. Because theyare endotherms, birds can maintain the high energy levels theyneed to fly. Birds have different ways to retain and release bodyheat to maintain a constant body temperature. When it is cold,feathers help reduce heat loss. Feathers fluff up and trap a layer ofair around the bird’s body. This limits the amount of heat that thebird loses.
When it is hot, birds flatten their feathers and holdtheir wings away from their bodies to release heat. Birds also pantto increase respiratory heat loss.Because birds are endotherms, they can live in all environments. Birds are found in the arctic regions and in the hot tropics.In order to maintain the high energy levels, birds and otherendotherms must eat large amounts of food.3. Evaluate What are theadvantages of being anendotherm rather thanan ectotherm?________________________________________________________________________Copyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.How do birds reproduce?Birds, like reptiles, reproduce by internal fertilization and theylay amniotic eggs.
Bird eggs have a hard exterior shell. Birds usually make a nest and lay their eggs in the nest. Nests may be madeof bits of straw and twigs or may be a depression in the sand.Some birds build nests that they add to every year. Birds incubateor sit on their eggs to keep them warm. Birds turn the eggs in thenest so that the eggs will develop properly. In some species, bothparents, male and female birds, take turns incubating the eggs. Inothers, only one parent incubates the eggs.
Bird eggs do not alllook the same. Often the species of bird can be identified by thecolor, size, and shape of an egg.READING ESSENTIALSChapter 31385NameDateClassSection31.2Birds, continuedDiversity of Birds4. What adaptations helpptarmigans live in colderclimates?________________________________________________________________________The basic form and structure of all birds are similar. They doshow differences, or adaptations, depending on where they liveand what they eat. Ptarmigans have feathered legs and feet, whichserve as snowshoes in the winter, making it easier for them to walkin the snow. Penguins do not fly.
Their wings and feet are modified for swimming. They have a thick layer of insulating fat ontheir bodies to help keep them warm. Owls have large eyes, a keensense of hearing, and sharp claws, which make them successfulpredators of the night. They can swoop down on their unsuspecting prey.The shape of a bird’s beak or bill indicates what kind of foodthe bird eats.
Hummingbirds have long beaks used to obtain nectar from flowers. Hawks have curved beaks that tear apart theirprey. Pelicans have large bills with pouches. They use the pouchesas nets for capturing fish. A cardinal has a short, stout beak forcracking seeds.Caudipteryx zoui386Chapter 31Scientists hypothesize that today’s birds comefrom an evolutionary line of dinosaurs that did notbecome extinct. They evolved.
Archaeopteryx is theearliest known bird in the fossil record.Archaeopteryx was about the size of a crow and hadfeathers and wings similar to a modern bird. It alsohad teeth, a long tail, and clawed front toes.Fossil finds in China support the idea that birdsevolved from a theropod dinosaur. It did not flyand it ran to capture its prey. It was about 1 m talland had feathers. The feathers may have helped toinsulate the animal or they may have been used forcamouflage. Scientists suggest that feathers evolvedbefore flight. The figure at the left pictures how atheropod dinosaur may have looked.Modern birds and theropods have other featuresin common.
Both have a sternum, a wishbone,shoulder blades, flexible wrists, and three fingerson each hand.READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Origins of BirdsNameDateClassSection31.2Birds, continued◗ After You ReadMini Glossaryendotherm: animal that maintains a nearly constant body temperature; it is not dependentupon the environmental temperaturefeathers: lightweight, modified protein scales;provide insulation, enable a bird to flyincubate: to sit on eggs to keep them warmsternum: breastbone1. Read the terms and their definitions in the Mini Glossary above.
Then use the space belowto write a brief paragraph explaining how birds fly and how they reproduce.________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________2. Use the diagram below to write the facts you have learned about each step of the respiratorysystem of birds.Copyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Cycle 1Inhalation 1Cycle 2Exhalation 1Inhalation 2Exhalation 2Visit the Glencoe Science Web site at science.glencoe.com to findyour biology book and learn more about birds.READING ESSENTIALSChapter 31387NameDateClassSection32.1 Mammal CharacteristicsSC.F.1.4.2 The student knows that body structures are uniquely designed and adapted for their function.SC.F.1.4.7 The student knows that organisms respond to internal and external stimuli.◗ Before You ReadYou may have had a dog that gave birth to puppies.
Even the friendliest mother dog may growlwhen someone attempts to come near her pups. How do the puppies benefit from the mother dog’sprotective behavior?______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________◗ Read to LearnCreate a Quiz After youhave read this chapter, createa quiz based on what youhave learned. After you havewritten the quiz questions, besure to answer them.Mammals are endotherms. They have the ability to maintaina fairly constant body temperature.
This enables mammals to livein almost every possible environment on Earth. Mammals havecharacteristics not found in other animals. Mammals have hairand produce milk to feed their young. Mammals have diaphragms,four-chambered hearts, specialized teeth, modified limbs, andhighly developed brains. The major structures of a fox, a mammal, are illustrated on page 389.What is the purpose of hair?1. What are two ways mammals lower their bodytemperature?________________________________________________Mammal hair is made of the protein keratin.
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