The Pony Fishs Glow: And Other Clues to Plan and Purpose in Nature - Term Paper Example

The Pony Fish’s Glow: And Other Clues to Plan and Purpose in Nature – Chapter Summaries Preface and Acknowledgements The book’s sub could also be The Adaptationist Program, but the one that the author chose was inspired by an address given by George Simpson. The author found the work to be fascinating and well presented, however lacking in some areas. The aim of The Pony Fish was to examine the adaptations of organisms both in terms of their strengths and weaknesses. The purpose of this was to show the limitations and the power of the process of evolution. Introduction: Plan and Purpose in Nature The plan and purpose of a man-made object is usually fairly obvious, it does not need to be examined. When examining human traits, modern biologists tend to not recognize elements of prior planning; rather such structures are perfected by the process of natural selection. The features, such as ears, are maintained because individuals with better versions of the feature are more likely to survive and reproduce. This is known as the adaptationist program. Petitioners of the program examine each trait in organisms, and look at how this relates to the way in which the organism survives to pass on its genes. Such questions get more complex as one looks at features more closely, such as the number of incisors in a jaw. The author summarizes his view of the study of biological adaptation in the first five chapters. He considers that adaptation is the development of something that is effective functionally from natural selection. He uses the pony fish as an example of this. This fish has a special type of light that helps it in many aspects of its life. However, other parts of its body aren’t as logical. For example, it only has two eyes, while more would make better sense given the environment which the fish exists in. Adaptationist Storytelling “The Sun exists to illuminate the surface of the Earth, and we have eyes to allow us to make use of the sunlight”. These two statements which the author considers imply a cause and effect relationship between the Earth and the Sun. However, when you examine the two statements more closely, you find that there is no evidence for the first being true while the second is not only true but has special implications. If the purpose of the Sun was to serve the Earth, why would it be so large in comparison, and why is the Earth so far away. The eye however, is a complex structure with many regulatory capacities and is clearly designed to enable the organism that possesses it to observe the world around them. If an eye is designed, then does there necessarily have to be a designer? Paley argues that for a watch to exist, it must have been created by someone who understood that there was a need to be able to tell the time. However, this analogy is not strictly true in the case of the eye. For example, why only two eyes (in humans) and why is the eye anchored by more muscles than it needs? In addition, some parts of the eye can be considered dysfunctional, such as the way that the eye is structured means that some light is lost creating a blind spot. The eyes of humans and other vertebrates have an upside down retina, which is impractical and can give rise to the medical problem of detached retina. In contrast, mollusks have retinas that are not upside down. Another example of functional design is the hand. The way that this works is precise functionally and allows for many different minute movements even though many different parts are involved. It has been argued that the hand is so perfect that there is no adjustments that could be made that can make it better. Prior to Darwin, the prevailing theory was that the complexity of design of all the different parts of organisms meant that there must be a designer. The idea of trial and error designed can be analogized to the development of the fishhook. Fishhooks have been found up to 50 thousand years in the past. These were originally made from bone or the edges of shells. Later, as the use of fishhooks developed, the use of a barb behind the point became prevalent as did other advances such as the use of metal as a material. Nowadays, fishhooks come in many different sizes, styles and variations. The way that fishhooks have developed and changed has been substantially influenced by selection. Fishhooks that were more effective at catching fish had an increased chance of being desired, consequently there would be an increase of that type of hook within the market. For the pony fish, it has a light producing organ inside its body which shines light downward, through the fish, producing a dim glow on the underside of the fish. This light actually acts as a form of camouflage. Functional Design and Natural Selection Darwin’s Theory of Evolution Darwin proposed that the process of natural selection drives the evolution of species. This theory is based off the observations that there is much variation, and that some of this variation is heritable and affects the survival of the individual. There is a struggle for survival with more offspring produced that can be maintained, and consequently those individuals with beneficial traits will survive to produce more offspring. If this continues over a substantial period of time than significant modifications could be observed. Different environment conditions can lead to different adaptations being favored, in time leading to diversification. Sexual Selection This occurs in addition to normal selection, and refers to adaptations which increase the likelihood of a male obtaining sexual access to females. Examples of this include physical competition between male deer or the feathers on a peacock. Many of these features may act against survival of the individual. Natural Selection and the Prevention of Evolution In many cases natural selection can act as an agent to prevent change. If a species is already well adapted, then many changes will make the individual less likely to survive, and consequently the change is unlikely to become prevalent in the population or species. Genetics, Molecular Biology and Modern Darwinism The inheritance of traits can be understood though the work of Mendel and subsequent genetic research. Genes are now known to be arranged on chromosomes in an almost linear sequence and that the chromosomes are present in pairs, one of each being delivered to gametes. Design for What? The theory of natural selection can be considered to have five important aspects. That variation is present that this variation is heritable, that there is a struggle for existence, which results in natural selection and survival of the fittest. What is an Adaptations Ultimate Purpose? Although the function of a body part such as an eye or hand may be easy to define, what is the ultimate purpose of such parts? The eye provides vision, but what is vision important for? One consideration is that the adaptation contributes to survival and reproductive success. Yet, even this is not without dissertation as reproduction will never result in the duplication of the individual (at least not sexual reproduction). Furthermore, reproduction is not the only way to ensure the prevalence of one’s genes, an individual may also do this by caring for brothers and sisters and their offspring. The Fundamental Importance of Genetic Success In some species, individual forgo their own reproductive success in order to ensure the success of their genes through caring for relatives. This is common in insects, however in mammals, adaptations focus on the survival and reproduction of the individual. The Scarcity of Individual Subordination to Group Interests Most actions and adaptations are performed to benefit the interests of the individual, rather than to ensure the survival or growth of the population or species as a whole. For the Harm of the Species Because adaptations focus on the benefit of the individual, they can often be detrimental or wasteful at the level of the species. For example, a ratio of 1:1 of the sexes is maintained in many species despite the fact that more females to males would produce more offspring. The Adaptive Body The genotype of an individual is often likened to the blueprint of a house, but this is a flawed analogy. You cannot liken a part of an individual to a specific point on the chromosome in the same way. Rather, genotypes contain instructions for instructions in a similar way to that of a computer program. Vitalism and Mechanism The manner in which the human body works can be described as being protein-based machinery. Scientists never conclude that physics and chemistry are insufficient to explain the biological phenomena that we observe. This effectively banishes any aspect of the supernatural as a descriptor and is known as mechanism. In contrast, vitalism assumes that chemistry and physics are not enough to describe the way the body works and consequently there must be a supernatural force at work. The Machinery of the Body The way that the body works can be analogized to that of a machine, with nerve impulses being similar to electric current along a wire. However, this can be misleading, as the transfer along a nerve is much slower than a wire. Brain as a Machine What drives a nerve to transfer an electrical impulse to a muscle? Even deep understanding of the structure of the brain does not lend itself to knowledge of the way in which it functions. The process of making decisions involves many small interactions between different parts of the brain. The Molecular Machinery of the Body At the molecular level, the body is extremely complex and well adapted with specialized structures for many different roles. An example is the mitochondrion, which has its own DNA and is involved in the process of energy acquisition from food and other sources. What Use Is Sex? The Origin of Sexuality DNA occurs in two strands, each complementary to the other. This provides advantageous for DNA proofreading. However, this does not always help, for example, if there are two errors one in each strand, there is no way for the proofreading mechanism to know which is correct and which isn’t. While errors in the genetic code are often immediately evident to the proofreading machinery, this is not always the case. Mutations can occasionally occur and bypass all mechanisms of proofreading. The importance of being able to repair genetic damage would have given primitive bacteria that possessed two copies of each gene. This mechanism would be able to lead sexuality through random chance if the two copies went separate ways. For a primitive cell, the most effective means of proofreading its genetic code would be to compare its genes to that of a similar source, that of a cell from another lineage. The two cells merge briefly before dividing. Each cell from the division obtains one copy of each gene from each parent cell. Thus, protecting the reliability and integrity of the genetic information may have been the original use of sexuality, but it is not so currently. Sexuality provides important recombination, which diversifies the offspring which can be especially important in unpredictable environments, particularly biologically uncertain environments. Why Eggs and Sperm? In multicellular organisms, usually the gametes are dissimilar in size with the egg being unusually large and the sperm tiny. Why does this occur? The smaller size of the male gamete allows for the production of many more sperm than if they were larger. The egg producing gender bears the cost of providing nutrients for the offspring and as a consequence the egg must remain large. In comparison, the sperm only contributes genetically to the next generation. Why be a Hermaphrodite? There are many examples of hermaphroditic species both those who are both sexes simultaneously and those who are one and then the other. Hermaphrodites do not generally fertilize themselves, although many species of plants can do so if no partners are available. In general, an organism is a hermaphrodite if the adaptations that serve one gender also serve the other, such as petals on a flower. Sex Ratio As examined in chapter three, the frequency of the sexes is an example of frequency-dependent selection. Size of Males In many species the females are larger than the males, and this is to be expected from the evolutionary perspective, as this has a directed effect on the amount of offspring that the females produce. In some species this difference can be extreme, with the male almost microscopic compared to the female. This can be effective as sperm contain little more than genetic information, and thus the size is not especially relevant. The Human Experience of Sex and Reproduction Human reproduction occurs generally (excluding identical twins) by the early embryo reproducing asexually. We reproduce sexually, with distinct male and female genders. Although sexual selection is present, it has little effect on the success to which offspring are raised. Pregnancy Producing an offspring is an important way for a mother to pass on her genes, yet although the two have interests in common, there are also conflicts of interest. A mother must allocate her provision to her offspring to take into account future offspring, her own health and other current offspring. Childbirth When childbirth occurs is another area of conflict between mother and offspring. For the offspring staying in the womb as long as possible is beneficial, while for the mother there are many advantages to giving birth earlier. Childhood Conflict again arises in childhood, with many examples of where the desires of mother and offspring conflict. An example of this is in weaning. Old Age and Other Curses Death is a part of life that cannot be ignored, and even if one survives accident and illness, they will eventually be killed by old age. Aging is distinct from the wear and tear of a machine, as many effects of aging are beneficial for an individual. As a person ages they become less effective at factors such as maintaining temperature, replacing materials and repairing wounds. What is Senescence? This is the constant decrease in precision for control that is available. As we age, many of our systems become less efficient. An Evolutionary Theory of Senescence Natural selection is influenced by survivorship and reproductive value. Senescence is a natural part of human life and is inevitable under natural selection, as it gives much higher priority to younger individuals. . The Wisdom and the Stupidity of the Body Evolution does not work from base; rather it only has the ability to work on already existing systems. Thus, humans have two pairs of limbs as a consequence of history, not what is optimal. Medical Implications In our current society, mortality is low in both middle age and youth as a consequence of the technology available to us. The result of this is many afflictions that plague those of old age, and while most are not terminal, they can be painful and/or debilitating. Such problems include, sight problems, hearing problems, sexual dysfunction and arthritis, as well as cardiovascular disorders and cancers. Why are we Mostly so Healthy? Our bodies work to maintain a balance of factors such as pH and temperature, even when conditions vary. Design Flaws that Lead to Illness Because of the way that natural selection builds on an already established blueprint, there are many inherent design flaws. An example of this is the position of the testicles, which have no reason to go below the ureter, which simply results in longer tubing. Medical Problems versus Biological Solutions When classifying the symptoms of a medical problem, not all are bad. For example, symptoms of a Streptococcus infection include high temperature, sore throat, headache and anemia. The anemia and fever come as a consequence of your body fighting the bacteria while the headache makes you less inclined to be involved in stressful activities. Abnormal Environmental Factors The human environment has changed radically over the last couple of thousand years through factors such as the prevalence of agriculture. Adaptations in our past are not necessarily beneficial in our present environment. For example, dental problems are common in current society, but are unlikely to have been so in early society. Philosophical Implications The earlier chapters of the book examined the human body, considering both the benefits and the flaws of this. The concept of God-is-good is difficult to correlate with natural selection. The Immorality of the Products of Natural Selection Infanticide is one example of a product of natural selection. This involves the killing of offspring of females in a tribe in order to increase the reproductive success of the males involved. Other Moral Fallacies Human life arises as part of a gradual process such as the acquisition of speech. The Wilson Manifesto This proposes that self-knowledge is shaped and constrained by aspects of the brain which have evolved through natural selection. Domain Mixes Four domains which are prevalent in philosophy are material, moral, mental and codical. Each of these involves a number of different factors. The mix of these domains is what defines the reason that people are the way that they are. Read More