Responses To Abiotic Factors - Practice Questions & MCQ

What is hemostasis:

• Homeostasis is any self-regulating process by which an organism tends to maintain stability while adjusting to conditions that are best for its survival.
• Body temperature control in humans is one of the examples of homeostasis.

Regulate:

• Some organisms are able to maintain homeostasis by physiological (sometimes behavioural also) means which ensures constant body temperature, constant osmotic concentration, etc.
• All birds and mammals, and a very few lower vertebrate and invertebrate species are indeed capable of such regulation (thermoregulation and osmoregulation).
• The mechanisms used by most mammals to regulate their body temperature are similar to the ones that we humans use. 
• We maintain a constant body temperature of  37^oC. 
• In summer, when outside temperature is more than our body temperature, we sweat profusely.
• The resulting evaporative cooling, similar to what happens with a desert cooler in operation, brings down the body temperature. 
• In winter when the temperature is much lower than 37^oC, we start to shiver, a kind of exercise which produces heat and raises the body temperature. 
• Plants, on the other hand, do not have such mechanisms to maintain internal temperatures.

Conform:

• 99 percent of animals and nearly all plants cannot maintain a constant internal environment.
• Their body temperature changes with the ambient temperature. 
• In aquatic animals, the osmotic concentration of the body fluids change with that of the ambient water osmotic concentration. 
• These animals and plants are simply conformers. 
• These conformers had not evolved to become regulators because thermoregulation is energetically expensive for many organisms. 
• This is particularly true for small animals like shrews and hummingbirds. 
• Heat loss or heat gain is a function of surface area. 
• Since small animals have a larger surface area relative to their volume, they tend to lose body heat very fast when it is cold outside; then they have to expend much energy to generate body heat through metabolism. 
• This is the main reason why very small animals are rarely found in polar regions. 
   

Migrate:

• The organism can move away temporarily from the stressful habitat to a more hospitable area and return when the stressful period is over.  
• Many animals, particularly birds, during winter undertake long-distance migrations to more hospitable areas. 
• Every winter the famous Keoladeo National Park (Bharatpur) in Rajasthan hosts thousands of migratory birds coming from Siberia and other extremely cold northern regions.

Suspend:

• In bacteria, fungi and lower plants, various kinds of thick walled spores are formed which help them to survive unfavourable conditions – these germinate on availability of suitable environment.
• In higher plants, seeds and some other vegetative reproductive structures serve as means to tide over periods of stress besides helping in dispersal – they germinate to form new plants under favourable moisture and temperature conditions. 
• They do so by reducing their metabolic activity and going into a date of ‘dormancy’.
• 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 desiccation. 
• Under unfavourable conditions many zooplankton species in lakes and ponds are known to enter diapause, a stage of suspended development.