Reading Essentials for Biology Glencoe (794133), страница 88
Текст из файла (страница 88)
Hair may haveevolved from scales. Hair provides insulation and waterproofing,which conserve body heat. If body heat becomes too high, mammals have internal mechanisms that signal the body to cool off.Mammals cool by panting and through the actions of sweatglands. Panting releases water from the nose and mouth, whichresults in a loss of body heat. Sweat glands secrete moisture ontothe surface of the skin. As the moisture evaporates, it transfersheat from the body to the surrounding air.How do mammals feed their young?Mammals have several types of glands, which are groups ofcells that secrete fluids.
Glands produce saliva, sweat, oil, digestive enzymes, milk, and scent.Mammals feed their young from mammary (MA muh ree)glands. These may be modified sweat glands, which produce388Chapter 32READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.What is a mammal?NameDateClassSection32.1Mammal Characteristics, continuedC HeartB DiaphragmA GlandsMost mammals have sweat, oil,mammary, and scent glands intheir skin.
Sweat glands helpmammals cool off. Oil glandslubricate the hair and skin.Foxes use their scent glandsto mark new territories.The diaphragm is a muscle thathelps the chest cavity expandto take in large amounts ofoxygen used to maintain thehigh metabolism of all mammals.It separates the chest andabdominal cavities.The four-chambered heart ofmammals enables them to keepoxygenated and deoxygenatedblood separate. This helps themmaintain their high metabolism.D TeethCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.A fox’s teeth indicatewhat it eats and howit gets food. Its caninesare used to punctureand tear the flesh ofprey. Its molars sliceand crush the fleshbefore swallowing.F HairE Mammary glandsDense, soft underhair insulates the fox by trappingwarm air next to its body.
The course, long guard hairsprotect against wear and may be colored for camouflage.The fox sheds its coat little by little during the summer.Like all female mammals, a femalefox nourishes her young with milkfrom her mammary glands.and secrete milk. Milk is a liquid rich in fats, sugars, proteins,minerals, and vitamins. Mammals nurse their young until theyoung are able to digest and absorb nutrients from solid food.How do the processes of respiration andcirculation work in mammals?Mammals need a high level of energy to maintain theirendothermic metabolism. Remember that metabolism is all thechemical reactions that occur in an organism.
The energy levelis maintained when large amounts of nutrients and oxygen enterthe body and reach the cells.READING ESSENTIALSChapter 32389NameDateClassSection32.1Mammal Characteristics, continued2. In addition to deliveringoxygen to cells, whatdoes circulation do?________________________________________________________________________The diaphragm of mammals helps expand the chest cavity toallow the flow of oxygen into the lungs.
A diaphragm (DI uh fram)is the sheet of muscle located beneath the lungs that separates thechest cavity from the abdominal cavity, where other organs arelocated. Once in the lungs, oxygen diffuses into the blood. As thechest cavity returns to its resting position, air is released.Like birds, mammals have a four-chambered heart. The bloodwith oxygen is kept completely separate from the blood withoutoxygen. This delivers a good supply of nutrients and oxygento cells, supporting endothermic metabolism.
Circulation alsoremoves waste products from cells and helps regulate body temperature. Blood helps keep a constant cellular environment,maintaining homeostasis.Teeth are a distinguishing feature of most mammals. Althoughfishes and reptiles have teeth, their teeth are all about the same.Mammals with teeth have different kinds that are adapted to thetype of food the animal eats. The pointed incisors of moles graspand hold small prey. The chisel-like incisors of beavers are modified for gnawing. A lion’s canines puncture and tear the flesh ofits prey. Premolars and molars are used for slicing or shearing,crushing, and grinding.
By examining the teeth of a mammal, ascientist can determine what kind of food it eats.Many hoofed mammals have an adaptation called cud chewing.Cud chewing breaks down the cellulose in plant walls into nutrientsthat can be absorbed and used. When plant material is swallowed,it moves into the first two of four pouches. Bacteria break downcellulose in the cell wall. The partially digested food, called cud, isbrought back into the mouth. After more chewing, the cud is swallowed again. When the food particles are small enough, they arepassed on to the other stomach areas where digestion continues.3. How do limb adaptationshelp mammals meet theirenergy needs?________________________________________________________________________What are the benefits of limb adaptations?Mammals have several adaptations for gathering food to meettheir energy needs.
For example, primates use their opposablethumb to grasp objects, such as fruits and other foods. Mammalshave other limb modifications. Moles have short powerful limbswith large claws that help them dig. Bats have long finger bonesthat support the flight membrane of their wings.Do mammals learn and remember?One reason mammals are successful is that they protect theiryoung, sometimes fiercely. They also teach their young survival390Chapter 32READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Why do mammals have varied teeth?NameDateClassSection32.1Mammal Characteristics, continuedskills. Mammals can accomplish complex behaviors, such as learning and remembering what they have learned.Primates, including humans, are perhaps the most intelligentanimals.
For example, chimpanzees can use tools, operatemachines, and use sign language to communicate with humans.The intelligence of mammals is a result of complex nervous systems and highly developed brains. The outer layer of a mammalian brain often is folded, forming ridges and grooves. Theseridges and grooves increase the brain’s active surface area.4.
Infer List animalbehaviors that illustrateintelligence.________________________________________________________________________◗ After You ReadMini Glossarydiaphragm (DI uh fram): in mammals, the sheetof muscles located beneath the lungs thatseparates the chest from the abdominal cavity; expands the chest cavity, which increasesthe amount of oxygen entering the bodygland: in mammals, a cell or a group of cells thatsecretes fluidsmammary (MA muh ree) gland: modified glandin female mammals, which produces andsecretes milk to feed their youngCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.1.
Read the terms and the definitions in the Mini Glossary above. Write a sentence using atleast two of the terms correctly.____________________________________________________________________________________________________________________________________________________________2. Match the concepts from Column 1 with the examples in Column 2.Column 1Column 21. Mammals maintain a fairly constantbody temperature.a.
highly developed brain_____2. Mammals learn and remember.c. endotherms_____3. Mammals regulate temperature byexcreting moisture.d. sweat glands__________4. Scientists can determine what amammal eats by examining teeth._____5. Mammals have modified limbs.b. opposable thumbe. specialized teethVisit the Glencoe Science Web site at science.glencoe.com to findyour biology book and learn more about mammal characteristics.READING ESSENTIALSChapter 32391NameDateClassSection32.2 Diversity of MammalsSC.F.1.4.2 The student knows that body structures are uniquely designed and adapted for their function.SC.G.1.4.1 The student knows of the great diversity and interdependence of living things.◗ Before You ReadYou may have seen kangaroos at the zoo. Write down all the information you know about kangarooson the lines below.
After you read this section, add the subclass to which kangaroos belong.______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________◗ Read to LearnIdentify MainPoints Highlight each subclass of mammal as it is introduced in this section.
![](https://s.studizba.com/z.php?f=/templates/si/i/noavatar.png&w=100&h=100&t=1"){kind=avatar}
