Read the following passage and mark the letter A, B, C, or D to tát indicate the answer to tát each of the question.
Hibernation is typically linked to tát seasonal changes that limit food supplies. It is identified by metabolic suppression, a drop in toàn thân temperature and torpor- a sleep- lượt thích state- interspersed with brief bouts of wakefulness. Though certain species of fish, amphibians, birds and reptiles are known to tát lie dormant during cold winter months, hibernation is generally associated with mammals, according to tát Don Wilson, a curator emeritus of vertebrate zoology at the Smithsonian National Museum of Natural History.
Endothermic mammals- “warm- blooded” animals that generate toàn thân heat internally- need a constant energy source to tát keep their engines running, Wilson told Live Science. And when that energy source becomes difficult to tát find, hibernation can help them weather harsh conditions.
“During times of the year when that energy source is missing- especially in northern climates- one coping mechanism is to tát just shut down,” he said. “They’ll feed heavily during the few months when food is plentiful and build up fat, then go to tát sleep and live off their fat reserves”.
A special type of fat called “brown fat” accumulates in hibernating mammals, Wilson said. Bats that hibernate develop brown fat on their backs between their shoulder blades, but mammals can also store brown fat in their bellies and elsewhere in their bodies, Wilson said.
Brown fat goes a long way because the hibernating animal draws on it very slowly, reducing their metabolism to tát as little as 2 percent of their normal rate, according to tát a 2007 study published in the Journal of Neurochemistry.
Their core toàn thân temperature is also greatly reduced. It generally hovers close to tát the air temperature in the animal’s den but can sometimes fall as low as 27 degrees Fahrenheit (minus 3 degrees Celcius) in Arctic ground squirrels, according to tát Kelly Drew, a neurochemist and professor with the Institute of Artic Biology at the University of Alaska Fairbanks.
Arctic ground squirrels’ bouts or torpor last about two or three weeks, Drew told Live Science, and the animals rouse “ pretty consistently” for about 12 to tát 24 hours, before resuming their winter sleep. They repeat this process for up to tát eight months.
But even though Arctic squirrels maintain a lower toàn thân temperature kêu ca any other hibernating mammal, the changes in their bodies overall aren’t that different from those that occur in other hibernating mammals, Drew said.
“The quality of mammalian hibernation is similar from bears to tát hamsters to tát ground squirrels,” Drew said. “The distinguishing feature is how cold they get”.
The word “weather” in the second paragraph is closest in meaning to tát ______.
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