Question

If the unfavourable conditions in the environment are localised or short-lived, which of the following responses is/are more likely to occur in organisms?

I. Hibernation
II. Diapause
III. Migration

• A. I, II and III
• B. Only I and III
• C. Only III
• D. Only II and III

Answer 1

The correct option is A I, II and III

Every organism in this world respond to the changes in the abiotic factors (temperature, pH) in its environment in different ways.

Some organisms prefer to regulate their internal environment to maintain a constant stable state irrespective of the changes in the external environment. They are called regulators. Examples include mammals and birds.

Some organisms such as plants and most invertebrates prefer to conform and change their internal environment according to the changes in their external environment. They are called conformers.

If the unfavourable changes in the surroundings are localised or transient, then organisms either migrate to a different environment or suspend their activities briefly to evade the stressful conditions.

Migration is the temporary movement of an organism from a stressful habitat (the natural environment in which an organism lives) to a more favourable one and then returning back to its original habitat, once the stress is over. For example, the Siberian Crane migrates to the warmer habitat of the Keoladeo National Park in Rajasthan during the harsh and cold winter season in Siberia.

Suspending the activities for a prolonged time, until the favourable conditions return, can also help to evade stressful conditions. Seed dormancy in plants is an example.

Animals can exhibit suspension of their activities in 3 different ways :

• Hibernation - A state of prolonged inactivity by sleeping during the winters. E.g., bears, bats, etc.
• Aestivation - A period of suspended activity during the summer months. E.g., crocodiles, salamanders, some land snails, etc.
• Diapause - A state of suspended development with reduced metabolic activity, in response to unfavourable conditions, seen in animal species such as insects, zooplanktons, etc. This mechanism holds the animal at a particular developmental stage (embryo, larvae, etc.) until the unfavourable conditions pass over.

Thus, all statements (I, II and III) are correct..