Adaptation
Animal adaptation is the alterations in the genetic and physiology which develop in an animal in response to internal and external stimuli. Adaptation is the evolutionary process whereby an organism becomes better able to live in its habitat(s) when they are continuously exposed to drastic environmental changes.
These animals establish functional and structural changes that enhance their potential to survive without stress in a unique environment. Therefore, animals with higher adaptive traits will be able to survive in harsh environmental conditions. Generally, adaptation is a long and slow process that takes generations to accomplish, which is rarely reversible.28.21.1 TypesofAdaptation
There are different types of adaptation as follows:
Genetic adaptation: It refers to the heritable animal characteristics that are transformed from one generation to the other, which favour survival of a population in a particular environment. This may involve evolutionary changes over many generations (selection by nature) or acquiring specific genetic properties (selection by man).
Physiological adaptation: It is the capacity and process of adjustment of the animal by itself, to other living things and to its external physical environment. Physiological adaptation signifies the changes that occur within an individual, over shorter or longer periods of time. This includes all the physiological changes that altered respiration rate, heartbeat, temperature, etc. exhibited by the animal which aids in maintaining homeostasis.
Biological adaptation: It refers to the changes with respect to morphological, anatomical, physiological, biochemical and behavioural characteristics of the animal which promote welfare and survival of the animal in a given environment.
Phenotypic adaptation: Phenotypic adaptations are the modifications that develop during the course of life of an individual due to changes in genetic or environment which are non-heritable.
Phenotypic adaptation is the changes in physical (development of callous) or behaviour of animals (domestication of wild animal).Nutritional adaptation: The availability nutrients for animals depend upon the climatic and ecological changes that have occurred in a particular place. The feed and fodder production are predominately reduced in climate change perspectives. The soil and water in the coastal areas of tropical regions contain low calcium due to leaching which is reflected in the pastures with low levels of this mineral. Therefore, it is very vital for the animals to adjust to the varying feed and fodder availability especially in the climate change scenario.
28.21.2 Adaptation Characteristics
Adaptation is an adjustment that decreases the physiological strain created by a constituent of stressful environmental factors. The degree of environmental stress may be quantified indirectly by the responses of the animal as strain or product of adaptation. Adaptation includes physiological alterations in the animal within its lifetime to the environment or genetic adaptation that involves forces of selection across generations. These adaptations may be restricted to a particular area of tissues or impacts the whole animal. Adaptation to hot environments can involve physical, behavioural, physiological and morphological changes. The physical adjustments are carried out by genetic selection or heritable characteristics which could be transferred from generation to generation. The subtropical cattle have dewlaps and longer limbs than temperate cattle to facilitate the heat dissipation. Variation in skin colour is also an adaptation feature to hot environments to modify the absorption of solar radiation. The lightcoloured coat of animal enhances the reflection of solar radiation away from the body during heat stress, and dark coat colour facilitates heat absorption in winter. The development of larger layers of subcutaneous fat and thermal insulation may result in a poorer heat tolerance but the same may be better adapted to cold.
In addition, the hair cover and shedding are also influenced by seasonal changes; most animals shed their winter hair as the summer approaches. The body size has an impact on adaptation to hot or cold environments. The superfluous large skin folds form larger surface area to favour heat loss per unit of weight in tropical animals and compact body conserves heat loss. The ears, dewlap, navel flap and vulva are larger, grooved and loosely attached to the body in heat-tolerant animals whereas temperate or cold-tolerant animals are more compact with no dewlaps and small hairy ears. The metabolic rate of heat adapted animals is lower than temperate species along with enhanced blood flow to the peripheries to enable heat loss via conduction and convection.Acclimatization: Acclimatization is a long-term adaptive physiological adjustment which results in an increased tolerance to continuous or repeated exposure to complex climatic stressors (normally produced under field conditions). When an animal voluntarily migrates from a mountain valley to a high altitude, its lung ventilation rate typically will increase initially to acquire adequate oxygen. After few days or weeks, lung ventilation begins to drop back towards the sea level rates as other physiological mechanism that facilitates gas exchange at high altitude. After several days, the individual is said to be acclimatized to a new high-altitude condition. The acclimatization is a rapid phenomenon wherein a series of physiological and/or biochemical adjustment takes place within the animal as a result of exposure to new environmental conditions. The typical characteristics of well-adapted animals are minimum weight loss when exposed to stressors, normally maintained reproductive rate, high resistance to diseases and high longevity with low mortality rate.
Acclimation: It refers to the adaptive changes that take place in response to a single climatic variable (normally produced in a laboratory or climatic chamber). For example, if an animal is placed in a hypobaric chamber by simulating high-altitude conditions, the animal becomes acclimated to the experimental conditions within a few days. The acclimatization and acclimation may be reversible.
Habituation (general): It is a gradual quantitative change of response which may lead to a loss of response, as a result of repeated stimulation.
Habituation (specific): It is the gradual reduction in sensation associated with a given repeated stimulus specific to the part of the body which has been repeatedly stimulated.
Learning: It is the acquisition of a new response, or a qualitative change of an existing response, or an inhibition or facilitation of an existing response by a new stimulus.
Conditioning: It is the transfer of an existing response to a new stimulus.
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