TOEFL iBT Practice Test 16

House Rules — 14 Sycamore Road • Kitchen: wash your own dishes within 24 hours. • Bathroom: clean it on your assigned week (see chart on the fridge). • Guests may stay a maximum of three nights in a row. • Bills are split equally and paid on the first of each month. • Please tell the others before inviting more than four visitors at a time.

Notice: Fire drill on Wednesday A fire drill will take place in the Humanities Building on Wednesday at some point between 10 a.m. and noon. The alarm will sound continuously. When you hear it, leave immediately by the nearest exit and go to the car park behind the sports hall. Do not use the lifts. Staff wearing yellow vests will check that every room is empty. You will be allowed back inside only when the all-clear is given.

Hibernation allows certain mammals to survive long periods when food is scarce and temperatures are low by dramatically reducing their metabolic rate, sometimes to less than five percent of normal activity levels. Unlike simple sleep, true hibernation involves a controlled, regulated drop in core body temperature, in some species to within a degree or two of freezing, alongside sharply reduced heart rate and breathing. What has puzzled physiologists for decades is how hibernating animals avoid the tissue damage that such extreme physiological slowdown would normally cause in an active mammal, including damage from reduced blood flow, and how they periodically rewarm their entire bodies from near-freezing temperatures within a matter of hours, a process that itself demands a tremendous, rapid burst of metabolic activity fuelled by specialised fat deposits. Ground squirrels, one of the most studied hibernators, cycle between deep torpor lasting one to three weeks and brief rewarming periods every so often throughout winter, even though each rewarming episode consumes a disproportionate share of their entire winter energy budget; the exact biological necessity for these energetically costly rewarming interruptions remains only partially understood, though hypotheses include a need to restore sleep debt or clear metabolic waste that accumulates during torpor. Medical researchers have taken considerable interest in hibernation physiology because understanding how these animals prevent blood clots and tissue damage during dramatically reduced circulation could eventually inform treatments for stroke, organ preservation for transplant, or even, speculatively, methods to place humans in medically induced states of suspended metabolism.