hibernation Flashcards
intro
Hibernation, aestivation, and diapause are survival strategies used by animals to cope with unfavorable environmental conditions, typically during extreme temperatures or resource scarcity. These processes involve physiological adjustments and control mechanisms that help animals conserve energy and endure adverse conditions.
1st para - hibernation
Hibernation is a prolonged dormancy during cold periods, primarily used by endothermic animals like bears, ground squirrels, and bats to survive food scarcity and harsh conditions. During hibernation, metabolic rates drop by up to 90%, and body temperature aligns with ambient temperatures (e.g., ground squirrels lower their temperature to near freezing). This reduction in metabolism is controlled by changes in the hypothalamus and hormonal shifts, especially reduced thyroid hormone, which lowers metabolic rates. The autonomic nervous system also slows heart and respiration rates and restricts blood circulation to non-essential tissues. Some species experience periodic arousals or torpor, where body temperature briefly returns to normal, allowing for metabolic functions like digestion (Carey et al., 2003) . These processes are regulated by circadian rhythms and environmental cues, enabling animals to survive extended periods without food.
2nd para - aestivation
Aestivation is a dormancy strategy used by animals like frogs, lungfish, and snails during hot, dry periods to prevent dehydration and overheating. For example, the African lungfish secretes a mucous cocoon, slowing its metabolism, reducing oxygen needs, and conserving water. Metabolic processes slow, protein synthesis changes to protect cells from dehydration, and heat-shock proteins and osmoregulatory compounds like glycerol help tolerate desiccation and temperature extremes (Lefebevre et al., 2004). Hormonal changes, such as reduced thyroid hormones, lower metabolic demands, similar to hibernation, enabling survival until more favorable conditions, like rain, return.
3rd para - diapause
Diapause is a dormancy strategy in arthropods, fish, and other invertebrates, occurring during unfavorable conditions like extreme temperatures or food scarcity. Unlike hibernation or aestivation, diapause happens during specific developmental stages (e.g., egg, larval, or pupal). Insects like monarch butterflies and fruit flies enter diapause in response to changes in photoperiod, temperature, or food availability. This process is hormonally regulated, particularly by reduced juvenile hormones, which suspend development. For instance, monarch larvae enter diapause in late summer, slowing growth and metabolism in response to shorter days and cooler temperatures. During diapause, metabolic activity drops, and cellular repair mechanisms prevent damage, allowing survival without feeding until favorable conditions return (Denlinger, 2002). This strategy conserves energy and aligns development with more favorable seasons.
Conc
Hibernation, aestivation, and diapause are vital survival strategies that help animals endure harsh conditions. These states involve metabolic reduction, hormonal regulation, and biochemical adaptations to conserve resources and prevent damage. Internal mechanisms like hormonal changes (e.g., reduced thyroid or juvenile hormones), circadian rhythms, and environmental cues (e.g., temperature, photoperiod) enable animals to survive extreme conditions and resume normal activities when conditions improve. These adaptations are essential for the survival and distribution of species in variable environments.
