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Class 12th Biology 2016 Set3 Delhi Board Paper Solution

Question 18

Explain with the help of suitable examples the three different ways by which organisms overcome their stressful conditions lasting for short duration.

Answer

Below are the different ways:

Migration: Organisms can move away temporarily from stressful habitat to a more hospitable area and return when stressful period is over. e.g. humans moving from Delhi to Shimla during summer.

Spore Formation : Various kinds of thick walled spores are formed which germinate on availability of suitable environment, e.g., bacteria, fungi etc. .

Dormancy: Seeds or Vegetative reproductive structures help to tide over stress by reducing their metabolic activity e.g., seeds or vegetative reproductive structures of higher plants.



Hibernation : In this organisms reduce their all matabolic activity, they undergo for a long period of inactivity. It takes place during winter e.g., bear.

Aestivation : It takes place during summer to avoid heat and dessication, They also undergo for a long period of inactivity  e.g., Snails/fish etc.

Diapause : Under unfavourable conditions, zooplanktons enter a stage of suspended metablic activity e.g., zooplanktons.