The term ‘Environmental physiology’ synonym ecological physiology is a part of biology which studies adaptations, changes, and effects on the physiological function of an organism due to its environment. We can say it causes minor variations in the physiological activities of a species of organisms because of its habitat. It is related to the process of evolution through natural selection.

Environment plays a crucial role in the selection of genes in that ecological area and is responsible for natural selection, for evolution. as the organisms with better physiology are likely to reproduce, and their offspring will be better suited for that area. Physiological changes due to the environment can have beneficial effects on organisms or can cause physiological diseases. We know, the environment refers to the physical world, and animals being heterotrophic eats food present in their environment, thus if the environment where the animal lives in great numbers then the things that are required by the animal for a healthy living its shortage or excess can lead to the development of various environmentally led diseases.

Environmental physiology

Environmental can be defined as the physical things which surround an animal’s body, be it chemicals in the surrounding, temperature, humidity, altitude, their food, their water, the nutritional value of their food, other animals in their environment, potential predators in their environment all make up or form the environment.

Same species living in different regions will have slight changes in their physiology better suited to their respective environment.

Effects of temperature on the physiology

We know that animals regulate and maintain their body at a specific temperature for metabolic activities.

Temperature regulation of a body is of two types,

1. Increasing the body heat in low temperature, cold conditions.
2. Decreasing the body heat in high temperature, hot conditions.

The body heat is regulated in many ways:-

• The contraction of blood vessels near the skin to prevent loss of heat.
• Fat deposition acts as insulation, which does not let body heat escape into the environment.  
• Body hair acts as an insulator and traps air in the mesh of hairs acting as an insulator, thus preventing heat loss.
• In a high heat environment, regulatory body temperature is maintained by sweating through the skin, or panting through the mouth to radiate excess body heat through the process of evaporation or,
• By expanding the blood vessels around the skin and the extremities of the body to dissipate excess heat through the means of conduction.

In both hot and cold temperatures, the animal needs to be properly hydrated, as it reduces strain on cardiovascular systems and the ability of the body to regulate heat by generating more energy. 

In hot temperatures, it is necessary to be well hydrated as sweating and panting lower the body temperature by evaporation of water which is secreted out through the skin in the form of sweat or by evaporation of saliva through the mouth. Lack of hydration may cause heat-stroke.

Effects of altitude on physiology

We know that as the altitude rises the air starts getting thinner and there is less oxygen present in the air which might be an issue for an animal not adapted to live in that region.

To overcome this problem there are some physiological changes, which take place,

• The partial pressure of oxygen is reduced in arteries
• The haemoglobin in blood is increased to help absorb more oxygen.
• The synthesis of red blood cells, RBCs are increased to carry more oxygen to and fro from the lungs to the tissues. Thus, the overall RBC number in the blood increases as altitude increases.
• The circulation is increased at first to help transport more oxygen to the tissues to function and later on steadies and becomes more efficient.

Sudden change in altitude can result in hypoxemia (oxygen deficiency in blood) or hypoxia (oxygen deficiency in tissues) and altitude-related diseases that can cause the death of unacclimatized animals.

Effects of lack of nutrients in the environment

Lack of a particular nutrient can cause diseases in animals concerning that nutrient. The presence of harmful substances like heavy metals like lead, mercury, arsenic, etc. can cause heavy metal poisoning, which leads to the death of the animal as heavy metal disrupts the normal physiological functioning of the body. The presence of Carcinogens, harmful chemicals can have adverse effects like stunting the growth of animals, development of various types of diseases, cancer, and even death.  

Effects of natural selection on physiology 

Natural selection is a process of evolution in which animals are best suited for an environment and can breed and produce offspring better suited for that environment.

Natural selection takes place in many ways – 

• Natural selection through abiotic means, for example- if the temperature of an environment decreases, animals with physiology more suitable will be better able to survive whereas animals that are not able to tolerate the cold will die and won’t be able to produce offspring.
• Natural selection through predator-prey or food availability, for example – In the Galápagos island, the tortoises there have two distinct shapes, on islands where there is a lack of food near ground the tortoise’s shell developed in such a way that there is bend upwards in the front upper side of the shell resembling a saddle so that the tortoise can easily bend its neck upward and eat the tall-growing cactus thus solving the food problem.

On islands where there is plenty of plants and vegetation near the ground, the tortoise didn’t need to bend upwards to reach tall vegetation, thus their shell is dome-shaped, thus different physiology in different islands with different availability of food. Thus, we can say that changes in physiology in reaction to environmental conditions facilitate the natural selection.

Conclusion

Environment plays a major role in the life of an organism, and animals living in a particular environment are well adapted both physiologically and evolutionarily to that environment.

Any changes in the environment affect the physiology of an animal as the bodily function of the animal changes and adjust to keep living in the environment according to the changes which took place. Environment impacts the circulation of blood through the body, heat regulation, metabolic activities, and energy production, and animals unable to adapt physiologically perish.  Environmental physiology facilitates evolution through natural selection, as environmental physiology or eco-physiology and evolutionary physiology are linked with each other.