INTRODUCTION
The organisation and development of molecular and organismal variations in nature, observed on a global, regional, and local level, follow structured patterns and are not arbitrary.
These patterns exhibit consistency across different forms of life and are positively linked to, and to some extent, can be anticipated by both the biotic and abiotic environmental diversity and challenges (Nevo 2001). As a branch of physiology, environmental physiology scrutinises the physiological responses of organisms to the diverse physical, chemical, and biological components within their surroundings. This field encompasses a wide range of topics to understand how animals function and respond to their natural environments at all stages of their life cycles, as well as how their bodies’ physiological processes deal with the effects of wide-ranging temperature, relative humidity (RH), radiant energy, precipitation, air circulation, atmospheric pressure, altitude, radiation, and pollution. Individuals or species demonstrate distinct responses to stimuli through unique behavioural patterns, thereby significantly impacting their ability to thrive in their natural surroundings. When animals are confronted with changes in their environment, they normally display one of three categories of response: avoidance, conformity, or regulation. Regulation, the major physiological aspect, can be defined as the maintenance of a constant internal environment under varying external environments, typically known as homeostasis. However, there are no perfect regulators and depending on conditions, some animals may behave as ionoconformers, osmoconformers, thermoconformers, or oxyconformers. The formal scientific exploration of the behavioural responses, reflecting how animals interact with their native environment and react to stimuli, is termed ethology.Bioclimatology, a subset of animal ecology, deals with the inter-relationships between components of the environment, viz., climate, soil, plants, and animals. A satisfactory environment is one that satisfies various criteria, like physical comfort without any manipulation in the design of the fixtures and fittings within the shelter, disease control without any stringent biosecurity measures, thermal comfort without any ameliorative actions, and lastly, behavioural satisfaction and physiological comfort.
When animals are continuously exposed to major environmental challenges, they slowly develop certain morphological and functional mechanisms that make them fit for those environmental conditions. Broadly, these coping mechanisms for extreme climatic conditions are categorised into habituation, acclimation, acclimatisation, genetic or biological adaptation, and phenotypic or physiological adaptation (Gaughan 2012). Acclimation refers to the synchronised phenotypic adjustments exhibited by the animal in response to a specific environmental stressor. In contrast, acclimatisation denotes a coordinated response to multiple concurrent stressors, encompassing factors like temperature, humidity, wind speed, and solar radiation. Both acclimation and acclimatisation mechanisms contribute to enhancing the adaptability of animals to dynamic climatic alterations. Correspondingly, adaptation involves genetic modifications that occur gradually over extended periods, aiming to mitigate the adverse effects of environmental variables on an animal’s biological systems as these stressors persistently impact the organism. In instances of extreme climatic conditions, animals display peculiar adaptive responses such as decreased metabolic rates or states of dormancy, which are manifested through mechanisms like sleep, torpor, hibernation, and estivation.24.2
Source:
Rana Tanmoy (ed.). Principles of Veterinary Animal Physiology. CRC Press,2026. — 290 p.. 2026
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