Homeostasis, Adaptation, And Evolution: Mechanisms Of Maintaining Equilibrium In Organisms Essay.

The constancy of the internal environment is the condition for a free and independent life.

In your answer, select some of the examples covered in lectures and practicals and use these to discuss the importance of this statement in relation to specific adaptations to extreme environments. For this essay, you should also use and reference (using the Harvard style format) specific examples from the academic literature (peer-reviewed scientific journals).

Discuss how scientific studies in selection and adaptation of natural populations help us understand the origin and the evolution of species. For this essay, you must use and reference (using the Harvard style format) specific examples from the academic literature (peer-reviewed scientific journals).

The concept of homeostasis and its origins

Anatomy is the basis of physiology. Claude Bernard supported the fact that physiological processes does not entirely depend upon the sole anatomy. This phrase can be linked with the concept of 'Milieu Interiur' which describes the mechanism by which an organism maintains its dynamic internal physiological equilibrium for sustaining in an external environment   exemplified by diversities.  This concept was later on termed as homeostasis, introduced by Walter Cannon in the 1930s (Cooper  2008).  As stated by Bernard, physicochemical or the humoral components cannot be dissected and constitute the internal environment. This concept combined with his principles of determinism gives way to new concepts of experimental medicine. In his writing he has opened up the fascinating fields of science, the one with adjustments, compensations or regulations (Cooper  2008). According to the Bernard equilibrium and constancy are not default conditions and the body has to achieve this through a continuous compensatory adjustment. Bernard had given for examples, such as the regulation of the water volumes in the body, regulation of the body temperature, metabolic stores and the oxygen concentration of the body (Perouansky 2012). Bernard articulated the necessity of maintaining an environment within the body that would allow the vital processes to be preceded independently of the physicochemical perturbations of the environment in which an organism lives. The various organ system of the body has got the capacity to fight with the adverse conditions of the environment and maintain a relatively stable and benevolent internal environment (Woods and Wilson 2013). Individual organisms have different requirements for achieving the overarching goal of sustaining the body temperature, pH, osmolarity. Furthermore all the organ system should be coordinated to maintain the supply of the essential commodities of the body such as oxygen and glucose to the vital organs and assuring adequate venous flow and blood pressure (Ursini et al. 2016).

The internal temperature of the human body shows a great example of homeostasis. A healthy and a fit body exhibit a temperature 98.6 º Fahrenheit. The body temperature can be controlled by releasing of the heat. As the hypothalamus senses the hotness of the body, changes are triggered to the effectors like the sweat glands and the muscles controlling the body hair for making the body cool by the secretion of sweat (Perouansky 2012). Hence the internal mechanism of the body helps to adapt to the internal changes.  Again when the body is attacked by a pathogen, the lymphatic system of the body comes in to play to maintain the homeostasis of the body and helps to fight infection with the body. When attacked by a pathogen, the brain can detect them and increase the body temperature causing the destruction of the pyrogens, buying more time for the immune cells to destroy the invaders (Ursini et al. 2016).

Examples of homeostasis in the human body and organisms in extreme environments

There are certain microorganisms that can survive in extreme environments and are broadly called as the extremophiles. These extremophiles can be found in very cold climate as low as -20 degree or deep ocean waters having high atmospheric pressure. Some of them are adapted to high osmolarity (Davies 2016). The psychrophilic organisms are faced with a number of challenges as extreme conditions slow down the kinetic energy of the molecules and also immobilize their enzymes. This is overcome by the changing the composition of their cell membrane such as by the addition of the branched fatty acid to the cell membrane. Their enzymes are also adapted to the cold temperature (Ursini et al. 2016). Bernard's concept of adaptation can also be seen in organisms residing in the deep sea hydrothermal vents where the water shoots out at about 300 ?. Some organisms such as Pompeii worms are found there, that is the world' most heat tolerant animal (Perouansky 2012). The concept of homeostasis can be inextrucably associated with the body functioning of the polar bears when it was recognized that it is actually the fatty layers of the skin that has the ability to maintain the 'internal milieu' of the organism to enjoy a physiologic freedom for surviving in an extreme environment. For maintaining the temperature at the thermal range and not being influenced by the arctic environment, they have layers of insulative fat and sub dermal vascularisations in order for maintaining the homeostasis in the body. The fur and the hairs also help in the insulation keeping their body warm in the extreme environment (Perouansky 2012).

Various researches on the signal transduction that regulates the expression of the genes or that causes biochemical modifications in the enzymes in response to the internal and the external stimuli, explains that the biological systems of the body are making continuous adjustments to the external environment. Cooper (2008) have experimented and have shown homeostasis in rats whose adrenal glands have been removed, compromising the sodium metabolism. They compensate for their uncontrolled sodium loss by consuming the hypertonic saline solution when provided. Maintenance of glucose level in the blood is necessary for keeping a person healthy. If the glucose level gets too high, insulin is released by the pancreas. Again if the blood glucose level is too low, then the glycogen in the liver is broken down to glucose molecules for maintaining the glycolytic pathway of the body (Davies 2016).

The role of various organ systems in maintaining the internal environment

Hence it can be said that, a body system is constantly adapting itself to the external environment to maintain a stable internal environment for attending equilibrium. This concept of homeostasis can be linked with a number of organisms who have adapted it to the extreme conditions. Maintenance of internal environment of the body does not occur by chance and is the result of the organized self government of the organisms (Davies 2016). The steady state conditions require that any chance towards change automatically meets the factors that oppose the changes. However there are many adaptations whose mechanisms and the reason for their life processes are yet to be discovered.

Evolution can be defined as a change in the feature of a species over successive generations relying in the process of natural selection (Dobzhansky 2013). Every living organisms starting from the microorganism to the chimpanzees have evolved from some species at some point of time. Evolution by Natural selection refers to a mechanism for change of a species over time (Wise 2012). Earlier to Darwin before his theories of Natural selection, concepts about the evolution can be found from the writings of Plato, the ancient Greek philosopher. The mechanism for the evolution was conceived of and described independently by the renowned scientists Charles Darwin and Alfred Russell Wallace. The concept of adaptation and natural selection came in to the lime light with the incidence of Darwin's visit to the Galapagos Island, where he observed that same species of organisms had distinct differences on different Islands (Darwin 2017). One of the most notable experiments done by Darwin, involved the Finches of Galapagos Island. He noticed and justified the varied sizes of the beaks of the bird on the basis of their food habits. For example, the seed eater finches had thicker and stronger beaks for breaking the seeds, whereas the seed eating finches had beaks in the shape of spears for stabbing their prey. Darwin has explained this mechanism as ' Natural selection' (Darwin 2017). Natural selection also known as "Survival of the fittest" refers to the sustainability of the organism due the presence of some favorable trait (Dobzhansky 2013). The favorable trait helps the organism to survive the environmental changes which ultimately leads to evolutionary change within a population (Darwin 2017). The trait eventually becomes predominant in the particular population. The theory of natural selection accounts for the adaptations in organisms, by equipping them with the innumerable features for the survival in the environment. It is due to the adaptations that accounts for the divergence of species from common ancestors. Adaptations may be termed as the heritable traits that help the organism in the survival and reproduction in an animal (Vitti et al. 2013). Darwin (2017) have described group of organisms getting adapted to the environment when there is a change in the range of the genetic variation that had taken place to maintain the fitness of the population. For example the presence of webbed feet in platypus is an adaptation for swimming. To decide on whether a trait is favorable or not depends upon the condition of the environment. For example the xerophytic plants had phylloclade structures that helped in the retaining of moisture in the desert climate which is unlike the plants that grow in normal climate (Furtak 2012).

The continuous adjustments made by the body in response to external stimuli

The evolution of these adaptations is caused by Natural selection.  According to the author, the evolution gives rises to group of organisms that have adaptive features that are very distinct from each other but share the basic anatomies like flowers. This type of evolution is known as a divergent evolution. Darwin (2017) has shown traits of evolution that have similar properties but does not have any recent common origin, known as the convergent evolution.

Dobzhansky (2013) had discussed about the concept of ecological speciation that says that reproductive isolation between populations arises from the effects of the divergent natural selection Furtak (2012) has focused on some points on adaptations by citing some striking examples.  Flabellina iodinea is a marine gastropod molluscs that are dangerous because of their stinging nematocytes that they acquire by feeding on the coral and storing these structures in their own body. Hence the creature has adapted itself to contain the poisonous cnidocytes in their body. Furthermore, author Richardson et al. (2012) have focused on the extraordinary modifications of the flower structure and the surprising mechanism of pollination. Cristie et al.(2012) have explained how adaptations like scent of a flower that mimics the attractive pheromone of a female bee in order to facilitate pollination. Many show adaptations by engaging in a cooperative behavior with its community such as the ants. Weaver ants construct the nests of living leaves by the coordinated work of numerous ants (Kingsolver et al. 2012).

Hence it can be said that evolution, natural selection are interrelated and take place one at a time. Organism possesses adaptive features that are approved by the nature for surviving in the nature. These favorable traits are passed on from one generation to the next by the process of evolution for a long period of time. The species that does not pose the adaptive features perish.

References

Christie, M.R., Marine, M.L., French, R.A. and Blouin, M.S., 2012. Genetic adaptation to captivity can occur in a single generation. Proceedings of the National Academy of Sciences, 109(1), pp.238-242.

Cooper, S.J., 2008. From Claude Bernard to Walter Cannon. Emergence of the concept of homeostasis. Appetite, 51(3), pp.419-427.

Darwin, C., 2017. On the origin of species by means of natural selection. Litres.

Davies, K.J., 2016. Adaptive homeostasis. Molecular aspects of medicine, 49, pp.1-7.

Dobzhansky, T., 2013. Nothing in biology makes sense except in the light of evolution. The american biology teacher, 75(2), pp.87-91.

Furtak, E.M., 2012. Linking a learning progression for natural selection to teachers' enactment of formative assessment. Journal of Research in Science Teaching, 49(9), pp.1181-1210.

Kingsolver, J.G., Diamond, S.E., Siepielski, A.M. and Carlson, S.M., 2012. Synthetic analyses of phenotypic selection in natural populations: lessons, limitations and future directions. Evolutionary Ecology, 26(5), pp.1101-1118.

Perouansky, M., 2012. The Quest for a Unified Model of Anesthetic ActionA Century in Claude Bernard's Shadow. The Journal of the American Society of Anesthesiologists, 117(3), pp.465-474.

Richardson, J.L., Urban, M.C., Bolnick, D.I. and Skelly, D.K., 2014. Microgeographic adaptation and the spatial scale of evolution. Trends in Ecology & Evolution, 29(3), pp.165-176.

Ursini, F., Maiorino, M. and Forman, H.J., 2016. Redox homeostasis: The Golden Mean of healthy living. Redox biology, 8, pp.205-215.

Vitti, J.J., Grossman, S.R. and Sabeti, P.C., 2013. Detecting natural selection in genomic data. Annual review of genetics, 47, pp.97-120.

Wise, P., 2012. Claude Bernard and the Milieu Intérieur: Origin and Evolution of the Concept. In Dialysis: History, Development and Promise (pp. 13-18). World Scientific.

Woods, H.A. and Wilson, J.K., 2013. An information hypothesis for the evolution of homeostasis. Trends in ecology & evolution, 28(5), pp.283-289.