essay on winter sleep of bears .word limit 500-1000
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Answer:
This is essay about winterbsleep of bears
Explanation:
Hibernation is a state of inactivity and metabolic depression in endotherms. Hibernation is a seasonal heterothermy characterized by low body-temperature, slow breathing and heart-rate, and low metabolic rate. It most commonly occurs during winter months.
Although traditionally reserved for "deep" hibernators such as rodents, the term has been redefined to include animals such as bears[1] and is now applied based on active metabolic suppression rather than any absolute decline in body temperature. Many experts believe that the processes of daily torpor and hibernation form a continuum and utilize similar mechanisms.[2][3] The equivalent during the summer months is aestivation.
Hibernation functions to conserve energy when sufficient food is unavailable. To achieve this energy saving, an endothermic animal decreases its metabolic rate and thereby its body temperature.[3] Hibernation may last days, weeks, or months - depending on the species, ambient temperature, time of year, and the individual's body-condition. Before entering hibernation, animals need to store enough energy to last through the duration of their dormant period, possibly as long as an entire winter. Larger species become hyperphagic, eating a large amount of food and storing the energy in fat deposits. In many small species, food caching replaces eating and becoming fat.[4]
Some species of mammals hibernate while gestating young, which are born either while the mother hibernates or shortly afterwards.[5] For example, female polar-bears go into hibernation during the cold winter months in order to give birth to their offspring.[6] The pregnant mothers significantly increase their body mass prior to hibernation, and this increase is further reflected in the weight of the offspring. The fat accumulation enables them to provide a sufficiently warm and nurturing environment for their newborns. During hibernation, they subsequently lose 15–27% of their pre-hibernation weight by using their stored fats for energy.[7]
Answer:
Bears are members of the family Ursidae, there are eight species alive today, with a large geographical range. They are found in North America, South America, Asia and Europe; they occupy a large range of habitats, from the Arctic tundra to temperate forests (Craighead Institute 2010). During winter, bears enter a state of dormancy.Hibernation is defined as “the dormant condition into which many animals and plants pass when the temperature falls below certain limits; esp. the winter sleep of some warm-blooded animals, as the dormouse, hedgehog, badger, bear, bBears endure the winter months in a condition of starvation, dehydration, mild hypothermia, hypotension and inactivity without bouts of active arousal. Although bears have depressed metabolic function during this period, defensive posturing and high respiratory rates in these animals within a very short period (seconds) of being disturbed has been observed. at etc.” s causes increasing lethargy and bears prioritise resting over calorie consumption, sleeping for up to 22 hours per day. This contributes to a decrease in physiological mechanisms such as heart rate, which gradually drops from 80 beats per minute to 66 per minute at rest Hibernation Induction Trigger (HIT) is found to induce hibernation in black bears (Ursus americanus) through sampling of plasma albumin, to which the small protein hormone is bound (Bruce et al. 1995). HIT has an opioid effect, binding to delta opiate receptors to cause hibernation in the winter. The effects are antagonised by mu and kappa opiate receptors, which may increase in number during the summer in the bear and oppose the induction of torpor during this time (Bruce et al. 1995).However the true effects, structure and regulation of HIT are not yet fully known, raising the question of how significant the hormone is in triggering winter torpor. Injection of bear HIT to ground squirrels (Spermophilus parryii) was capable of causing summer hibernation and decreased muscle contractility (Bruce et al. 1995). Polar bears (Ursus maritimus) do not enter true winter dormancy yet retain high winter albumin concentrations of HIT still causing summer hibernation in ground squirrels (Bruce at al. 1990). Hibernation may be “a case of convergent evolution, no hibernation factor should be expected to be universal in promoting hibernation” so each bears species may have a differently structured HIT molecule (Bruce et al. 1990).