Q. Consider the following:
- Hibernation
- Migration
- Diapauses
- Aestivation
Which of the above mechanisms are adopted by animals to overcome stressful external conditions?
Answer:
All of the above
Notes: If the stressful external conditions are localised or remain only for a short duration, the organism has two other alternatives for survival. The organism can move away temporarily from the stressful habitat to a more hospitable area and return when stressful period is over. In animals, the organism, if unable to migrate, might avoid the stress by escaping in time. The familiar case of bears going into hibernation during winter is an example of escape in time. Some snails and fish go into aestivation to avoid summer-related problems-heat and dessication. Under unfavourable conditions many zooplankton species in lakes and ponds are known to enter diapause, a stage of suspended development.