It is difficult to compare the part of the textbook that I have read, which deals with evolution in relation to adaptation, with specific concepts that were discussed in class, due to the different styles of teaching that the book and the class utilize. The class discussions were normally overview of the subjects, because there was not enough time to delve into the nuances of each discussion topic; conversely, the book has the liberty to take more time to explain difficult concepts somewhat more in depth, which is not possible in class. The scope of the book helped explain the topics that were minimally discussed in class; however, the book failed to portray science as it was discussed in class, as a means of discovery instead of a definite body of facts and laws.
The section on adaptation starts by outlining Darwin’s Theory of Evolution, referring to it as “the unifying principle of modern biology” (Keeton 669); it then differentiates between evolution and natural selection. Natural selection is based on five ‘rules,’ so to speak:
“more offspring are produced than can survive to reproduce (excess progeny); the characteristics of living things differ between individuals of the same species (variability); many differences are the result of inheritable, genetic differences (inheritability); some differences affect how well adapted an organism is to its environment (differential adaptiveness); and some differences in adaptedness are reflected in the number of offspring successfully reared (differential reproduction)” (Keeton 669).
The five concepts relate to our lab findings that most characteristics are controlled by both genes and the environment; those findings apparently apply not only to the human body, but also to nature as a whole. Natural selection is not only decided by inherited genes, differential adaptiveness, but also by the environment that the organism lives in, variability.
During the beginning of the semester, I was startled by the role that randomness played in biological processes. After being told for years that science was the definitive answer, I was unsettled by the idea of random things occurring, from the cellular level up. Now, I realize that randomness is what aids variation in creatures, as well as lead to genetic disorders; it can be both a positive or negative force in biology. However, after years of hearing nothing about randomness in biology classes, I was shocked to read about it in this textbook. It enhanced what I had already discovered during class; while much of life was already predetermined by genes, there is always the chance of random behavior throwing a wrench in the system, resulting in biological changes that can forever alter a person’s genetic makeup.
A perfect example of the attributes of randomness is the Hardy-Weinberg Law, which, though slightly idealistic in its design, relies on random instances to occur, thus demonstrating “that variability and inheritability, the two bases of natural selection, cannot alone cause evolution” (Keeton 676). The five parts of the law state that “the population must be large enough to make it highly unlikely that chance alone could significantly alter allelic frequencies, mutations must not occur, or else there must be mutational equilibrium…, there must be no migration of members into or out of the gene pool, mating must be totally random, [and] reproductive success… must be totally random” (Keeton 676). This law, while good in theory, cannot be applied in real life, because few situations exist where all five parts can be met. The role of randomness in the last two parts is very important, and helps account for the variation and evolution of the population; however, the book is quick to point out that “these conditions are never completely met, and so evolution does not occur” (Keeton 676). The first three parts are so unlikely that they become counter-productive for the latter two parts. The Hardy-Weinberg Law can also be disproved by genetic drift, which is random evolutionary change, and is not “influenced by the relative adaptiveness of the different alleles” (Keeton 678).
The book conversely shows how many attributes of biology, still related to natural selection and evolution, are strongly influenced by genetic factors. It goes to great depths, with many genetic computations, to show the ratios and expected probabilities that will occur when different characteristics are crossed. It showed allelic ratios as the norms, which, as I learned in lab, is not always what happens in life.
The textbook uses multitudes of laws and rules to convey the underpinnings of biology; but as we have learned in class, there are no absolutes in science. Everything that is portrayed as the scientific be all and end all in the book is simply a story attempting to explain how things occur in the body, as well as in nature. Sure, the book had a myriad of facts, allowing it to explain everything and anything biology-related, but it took itself too seriously; however, to its credit, it portrayed life as what it appears to be, a mix of predisposed characteristics and random evolutionary change. Though the book provides facts as the basis of its information, it is also quick to point out the weak points of certain concepts. For example, after it goes into depth describing the ways in which evolution is influenced by many factors, it then warns, “As this hypothetical example indicates, evolution does not depend exclusively on any single particular mechanism, whether natural selection, genetic drift, mutation, or migration. It also underscores the potential error of assuming that all the traits of the living things around us are necessarily the adaptive result of natural selection” (Keeton 680). While the mission of the book is to teach biology to eager students, it also acknowledges that some of the things that it is trying to teach are not fully applicable; however, it portrays science as a body of facts, not as an exploration of life and its processes. Conversely, the class allowed the students to explore what we did not know, but it also forced us to rethink what we have always believed to be true, because it was stated in a textbook. This book, with all of its contradictory laws and ideas, has helped me realize that science is still an evolving theory, a process of “getting it less wrong.”
Works Cited
Keeton, William T. and Carol H. McFadden. Biology: An Exploration of Life. New York:W.W.
Norton & Company, 1995.
Comments