{"product_id":"9781450033664","title":"Adaptations in the Animal Kingdom","description":"Chapter 1  \u003cbr\u003eTemperature Regulation in Animals  \u003cbr\u003eThere are, broadly speaking, two kinds of animals with regard to body  \u003cbr\u003etemperature: exothermic (cold-blooded) and endothermic (warm-blooded)  \u003cbr\u003eanimals. The exothermic animals, such as reptiles, do not supply body heat  \u003cbr\u003eby metabolic conversion of food to heat. Reptiles allow their surroundings  \u003cbr\u003eto determine their body temperature. They lie out in the sun to warm their  \u003cbr\u003ebody. If they are too hot, they seek the shade or even burrow into the ground.  \u003cbr\u003eAt night they hide from the cold in burrows or squeeze into cracks between  \u003cbr\u003erocks or hide in leaf cover. Reptiles avoid the extremes of temperature. When  \u003cbr\u003ereptiles become cool, their movements slow down, and chemical processes  \u003cbr\u003ein their bodies, such as digestion, are inhibited. Predators, such as hawks  \u003cbr\u003eand eagles, find it easier to prey on lizards and snakes in cooler weather. The  \u003cbr\u003edistribution of reptiles is somewhat limited by their exothermic character.  \u003cbr\u003eThey do not thrive in cold climates1.  \u003cbr\u003eWhat are the advantages and disadvantages in being exothermic? When  \u003cbr\u003ethe lizard is in a cool environment and cannot find a warmer spot, its body  \u003cbr\u003esimply cools to the temperature of the surroundings. It is not necessary for  \u003cbr\u003ethe exothermic lizard to generate heat to increase its body temperature.  \u003cbr\u003eThis means that the lizard uses less energy and does not have to eat as  \u003cbr\u003emuch. As the lizard cools its digestion, breathing rate and heart rate slow,  \u003cbr\u003esaving energy. A disadvantage occurs when the cool lizard is attacked by  \u003cbr\u003ea predator. If warm, he could run fast and have a much better chance of  \u003cbr\u003e1 St. Patrick did not chase the snakes out of Ireland. Ireland was already completely free of  \u003cbr\u003esnakes. St. Patrick was instrumental in converting pagans to Christianity. Since the snake was  \u003cbr\u003ea symbol used in pagan rituals, St. Patrick was influential in ridding Ireland of the ritual use  \u003cbr\u003eof symbolic snakes.  \u003cbr\u003e10 Verne A. Simon  \u003cbr\u003eevading capture. A warm lizard being chased by a predator can move quite  \u003cbr\u003efast for a short distance, but like other exotherms, lacks endurance and  \u003cbr\u003esoon tires. When the exotherm is running fast, its effort is anaerobic, that  \u003cbr\u003eis, is not using oxygen, and lactic acid is building up in its body. It soon  \u003cbr\u003etires and is unable to exert itself. It must recover by taking in oxygen to  \u003cbr\u003erid the body of lactic acid. Another disadvantage of exothermic life is that  \u003cbr\u003ecold climates are not available as habitat. If there is a sudden climate  \u003cbr\u003echange, an exothermic animal wouldn't be able to mount the sustained  \u003cbr\u003eeffort needed to migrate to a better environment. The exothermic creature  \u003cbr\u003emight simply perish.  \u003cbr\u003eAbout 180 million years ago, mammals appeared. Mammals are  \u003cbr\u003eendothermic (warm-blooded) and are able to maintain a nearly constant body  \u003cbr\u003etemperature regardless of the temperature of their surroundings within wide  \u003cbr\u003elimits. Their bodies will not tolerate too high or too low a temperature. If the  \u003cbr\u003esurroundings are too hot or cold, causing the body temperature to exceed  \u003cbr\u003eallowed limits, the animal will die. Mammals have furry coats to help them  \u003cbr\u003etolerate low temperatures. Sea-dwelling mammals-whales, seals, and  \u003cbr\u003ewalrus-have thick layers of blubber for insulation. Birds are endothermic and  \u003cbr\u003ehave feathers to protect them from the cold. Many types of birds and mammals  \u003cbr\u003esurvive in cold climates. Emperor penguins even live in the Antarctic, in the  \u003cbr\u003ecoldest climate on earth. Under normal circumstances, mammals and birds  \u003cbr\u003emanage to keep this very nearly constant body temperature regardless of  \u003cbr\u003ethe temperature of their surroundings. Mammals are characterized by having  \u003cbr\u003ebody hair and suckling their young. This latter behavior gives the class its  \u003cbr\u003ename; mammals must have mammary glands. A second advantage is that  \u003cbr\u003eendothermic animals are not limited to activity only in daylight hours. In  \u003cbr\u003emany locations, it is too cold at night for exotherms to be active. Even very  \u003cbr\u003ecold temperatures do not exclude endothermic animals such as mammals  \u003cbr\u003eand birds from nocturnal activity. Exothermic animals are not normally found  \u003cbr\u003ein cold climates, though there are a few exceptions. Mammals with their hair  \u003cbr\u003ecan grow warm fur coats as in the polar bear or beaver. Mammals with little or  \u003cbr\u003eno hair often have a thick subcutaneous layer of fat for thermal insulation as  \u003cbr\u003ein walrus and whales. Birds have feathers for insulation, like the snowy owl,  \u003cbr\u003ewhose white feathers match the snow.  \u003cbr\u003eDuring long periods of cold weather (winter), some, but not all, mammals  \u003cbr\u003ehibernate. Their body temperature drops to a few degrees above freezing, and  \u003cbr\u003etheir breathing and heart rates almost cease. Other mammals, such as bears,  \u003cbr\u003eundergo estivation. Their body temperature may drop by 40oF (22oC). While  \u003cbr\u003ein estivation, they live off the fat they have accumulated in preparation for  \u003cbr\u003ewinter. They may become active for short periods on relatively warm days.  \u003cbr\u003eSome animals tough it out in winter, like emperor penguins and moose.  \u003cbr\u003eAdaptations in the Animal Kingdom 11  \u003cbr\u003eMammals in cold latitudes develop furry coats to retain heat during cold  \u003cbr\u003ewinters. Mammals in warm climates may have very sparse hair, for example,  \u003cbr\u003eelephants and naked mole rats. Some mammals (sheep, horses, cattle) give  \u003cbr\u003ebirth to single young with well-developed senses of sight and hearing and with  \u003cbr\u003emusculature ready for walking within minutes of birth. Such well-developed  \u003cbr\u003eyoung are said to be precocial.  \u003cbr\u003eIn contrast to precocial young are altricial young, born in litters, with  \u003cbr\u003eclosed eyes, closed ear canals, having no capability of locomotion, and  \u003cbr\u003eoften sparsely covered with hair or feathers. Some examples of endothermic  \u003cbr\u003ealtricial young are dogs, cats, rats, mice, and polar bears. Human babies  \u003cbr\u003eare neither clearly altricial nor precocial. At birth a human baby's eyes are  \u003cbr\u003eopen and the baby can hear. On the other hand, a human infant is naked and  \u003cbr\u003eunable to move about. Humans usually are born singly. Altricial animals are  \u003cbr\u003eusually born in litters and are small. Because of their small size they have  \u003cbr\u003ea large surface to volume ratio, which makes it more difficult to maintain a  \u003cbr\u003econstant body temperature as required by endothermic animals.  \u003cbr\u003eHow do altricial young cope with temperature fluctuations? Some animals  \u003cbr\u003esuch as puppies and kittens have numerous litter mates with which they  \u003cbr\u003ecan huddle, thereby decreasing their exposed surface area. Mothers share  \u003cbr\u003ebodily heat with their offspring and provide warm milk as a buffer against  \u003cbr\u003ethe cold. There is a special organ for heat production in young altricial  \u003cbr\u003eanimals, that is, brown adipose tissue (BAT). Heat production by BAT is  \u003cbr\u003estimulated by cold temperatures and by norepinephrine2 (noradrenaline).  \u003cbr\u003eBAT is present in large amounts in the young, constituting about 5% of  \u003cbr\u003ebody weight. In adults, BAT constitutes only 1% of body weight and has  \u003cbr\u003etraditionally been regarded as unimportant. Adults are able to raise their  \u003cbr\u003ebody temperature by the muscular activity, including shivering, but infants  \u003cbr\u003eseem unable to shiver. Human babies have BAT deposits in the neck and  \u003cbr\u003ebetween the shoulder blades. Heat production by BAT in human babies  \u003cbr\u003ecan be demonstrated by infrared photography. An unclothed baby lying  \u003cbr\u003eprone at room temperature shows hot spots between his shoulder blades  \u003cbr\u003eand in the area of his neck in an infrared photo. The distribution of BAT has  \u003cbr\u003eimportant advantages. It is very helpful in keeping the heart and brain from  \u003cbr\u003ecooling. Both of these organs show decreased activity if the temperature  \u003cbr\u003edrops. The placement of BAT on neck and shoulders aids in keeping the  \u003cbr\u003ebrain and heart warm.  \u003cbr\u003eBAT is brown due to pigmented organelles called mitochondria within  \u003cbr\u003ethis special tissue. The BAT is very rich in mitochondria. Mitochondria are  \u003cbr\u003e2 Epinephrine (adrenaline) is a hormone produced by glands at the top of the kidneys. Epi  \u003cbr\u003emeans \"above\" and nephrine refers to the kidney. Norepinephrine is an active metabolite of  \u003cbr\u003eepinephrine. Both epinephrine and norepinephrine prepare animals for \"fight or flight.\"  \u003cbr\u003e12 Verne A. Simon  \u003cbr\u003epresent in most b","brand":"Xlibris Corporation","offers":[{"title":"Default Title","offer_id":47107217424624,"sku":"9781450033664","price":8.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0737\/7593\/9824\/files\/9781450033664_p0.jpg?v=1763832966","url":"https:\/\/shop-qa.barnesandnoble.com\/products\/9781450033664","provider":"Barnes \u0026 Noble (DEV)","version":"1.0","type":"link"}