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Toefl ibt internet based test 2006 - 2007 part 6

Chapter 3 contains a summary of the academic skills that you will need to complete the tasks on the Next Generation TOEFL. Read the strategies, complete the practice activities, and check your answers. By going systematically through this chapter, you will acquire valuable academic skills. Take your time and learn them well | 2B MODEL TEST 1 PRETEST - Through metabolic heat production insulation and vascular adjustments birds and mammals are capable of astonishing feats of thermoregulation. For example small birds called chickadees which weigh only 20 grams can remain active and hold body temperature nearly constant at 40cC in environmental temperatures as low as -40 C as long as they have enough food to supply the large amount of energy necessary for heat production. Many mammals and birds live in places where thermoregulation requires cooling off as well as warming. For example when a marine mammal moves into warm seas as many whales do when they reproduce excess metabolic heat is removed by vasodilation of numerous blood vessels in the outer layer of the skin. In hot climates or when vigorous exercise adds large amounts of metabolic heat to the body many terrestrial mammals and birds may allow body temperature to rise by several degrees which enhances heat loss by increasing the temperature gradient between the body and a warm environment. Evaporative cooling often plays a key role in dissipating the body heat. If environmental temperature is above body temperature animals gain heat from the environment as well as from metabolism and evaporation is the only way to keep body temperature from rising rapidly. Panting is important in birds and many mammals. Some birds have a pouch richly supplied with blood vessels in the floor of the mouth fluttering the pouch increases evaporation. Pigeons can use evaporative cooling to keep body temperature close to 40 C in arr temperatures as high as 606C as long as they have sufficient water. Many terrestrial mammals have sweat glands controlled by the nervous system. Other mechanisms that promote evaporative cooling include spreading saliva on body surfaces an adaptation of some kangaroos and rodents for combating severe heat stress. Some bats use both saliva and urine to enhance evaporative cooling. Glossary ATP energy that drives certain .