Thursday, April 12, 2012
Shenk proposes that "researchers have recorded a constellation of physical changes (occurring in direct response to practice) in the muscles, nerves, hears, lungs, and brains of those showing profound increases in skill level in any domain"(67). Does this imply that with practice to be faster, stronger, efficient, organisms can "adapt" or achieve selective advantages? Distinguish what Shenk's claim is from the rudimentary definition of evolution.
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Evolution is defined as the adaption of a specific organism from generation to generation (Cambell 456). It does not, however, mean an adaption of a single organism throughout its life time. Shenk's claim towards the ability of individuals to adapt to the environment is not evolution. Instead it is the bodies ability to change in order to reach homeostasis more efficiently in a specific environment. With practice specific processes, cells, and behavior will adapt in order for the body to more efficiently maintain homeostasis. During practice, such as exercise, the body must preserve homeostasis. Exercise requires our muscle cells to work harder than usual, therefore the cells lose oxygen and nutrients. In order to maintain homeostasis in the cell our bodies react. Our breathing rate increases in order to get more oxygen into the blood and "the pancreas secretes the hormone glucagon into the blood...which promotes the breakdown of glycogen in the liver and the release of glucose into the blood" (Campbell 893). The body has these reactions in order to maintain homeostasis of oxygen and monosaccharide levels. After continuos and strenuous exercise, the body will eventually adapt in order to more efficiently maintain homeostasis of processes and cells that are specific to the practice done. In other words, the "challenge of homeostasis...[which] will trigger the activation of some genes in massive storage of dormant genes within the cells' DNA" (Shenk 254-255). The constant challenge to homeostasis due to practice causes certain genes t be activated. Based on the GxE model the activation of genes due to homeostasis will lead to the development of unique traits. For example, professional weight lifters experience a hormonal adaption, they see an "increases in the concentrations of serum testosterone, luteinizing hormone (LH), and follicle-stimulating hormone (FSH)" (http://jap.physiology.org/content/65/6/2406.abstract). Because weight lifting challenges the homeostasis of nutrients and oxygen in the muscles, and because the specific practice of weight lifting is continuous and strenuous, the body adapts to increase the presence of certain hormones in order to maintain homeostasis more efficiently.
ReplyDeleteThe ability of the body to adapt in order to maintain homeostasis more efficiently is not the same thing as evolution. The rudimentary definition of evolution involves a significant adaption that can be seen between two different generations. This type of adaption will cause the particular organism with the adaptation to be better fitted to the environment, allowing it a better opportunity for this organism to survive and reproduce. The increase of population of an organism with a specific adaption will cause there to be a slight change in species between the original organism and the adapted ones. Conversely, the adaptions that take place after strenuous practice are not adaptions that will eventually create a new species, or even pass down to future generations, instead the adaption created after consistent strenuous practice is a response the body makes in order to more efficiently maintain homeostasis.
Joseph Hugener (jah1112@comcast.net)
With a significant amount of practice, the human body can adapt to accommodate the demands of its environment due to the GxE theory. Whether someone has a genetic predisposition toward large muscles or not, if a person exercises consistently, their muscles become stronger and more efficient through chemical regulation. The physical stress of exercise stimulates protein synthesis (including Actin and Myosin) in muscle tissue used for the activity, which causes the cells in that area to swell. Actin and Myosin are “contractile proteins”, so as the concentrations of these proteins increase, so does the power of the muscle cells. However, “much of the strength gains seen in women and adolescents” is due to the body’s ability to “recruit more muscle cells,” (synchronous activation), increasing the amount of power a muscle may exert upon contraction without forcing each cell to withstand a larger workload. With training, the body adapts to inhibit neural responses to feedback from the muscles as well, ensuring that muscles are not overtaxed (http://www.scientificamerican.com/article.cfm?id=how-does-exercise-make-yo). In an environment where more strength is required in daily life, the ability to adapt and become stronger is a huge selective advantage for humans, as is a natural tendency toward large, strong muscles; possessing either of these characteristics will increase the likelihood of survival and reproduction.
ReplyDeleteThe difference between adaptation and evolution is simply one of scale. Adaptation is when reversible changes take place within an organism to make it easier for that organism to survive in a certain environment. Evolution is when adaptation of a population due to a selective pressure over several generations leads to the formation of an entirely new species (http://www.talkorigins.org/faqs/evolution-definition.html). It is the same general principle, only evolution is more widespread and far more permanent.
(Rachael Affenit, rachael.affenit@comcast.net)