Class 12 Biology Organisms and Populations Responses to Abiotic Factors

Responses to Abiotic Factors

Abiotic conditions of many habitats may vary drastically in time and the organisms living in such habitats cope with stressful conditionsby maintaining the constancy of their internal environment.

The process of maintain a constant internal environment is called homeostasis

The organisms which are able to maintain homeostasis are called regulators and the organisms which are not able to maintain homeostasis are called conformers

Organisms are able to maintain homeostasis by physiological and behavioral means which ensures constant body temperature, constant osmotic concentration.

All birds and mammals, very few lower vertebrate and invertebrate species are capable of thermoregulation and osmoregulation.

Human maintain a constant body temperature of 370

Humans maintain homeostasis by sweating in summer and shivering in winter.

Conformers cannot maintain a constant internal environment and 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.

Conformers had not evolved to become regulators because thermoregulation is energetically expensive for many organisms as heat loss or heat gain is a function of surface area.

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 that is why very small animals are rarely found in polar regions.

Conformers cope with the stressful conditions by various alternate responses which are-

  • Migrate –the birds move temporarily to hospitable areas from stressful habitat. For example- birds from Siberia and extremely cold regions migrate to Keolado National Park (Bharatpur) in Rajasthan.

Fig. Bharatpur, Rajasthan

  • Suspend

Sporulation- thickwalled spores are formed which help the organisms to survive under unfavorable conditions and the spores germinate on availability of suitable environment. Example- bacteria, fungi, lower plants.

Dormancy – to tide over the periods of stress seeds of higher plants and other vegetative reproductive structures reduce their metabolic activity and go into a state of dormancy which germinate to form new plants under favorable conditions.

Hibernation and aestivation- if the organisms are unable to migrate they avoid the stress by escape in time where the organisms sleep in winter called as hibernation or sleep in summer called as aestivation. Example- bears sleep in winter and snail sleeps in summer.

Diapause- the process of delay in the development during adverse environmental conditions is called diapause. Example- zooplanktons.

Fig. zooplankton           

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