Darwin’s Theory
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Darwin’s Theory
Darwin was not the first to consider evolution as a process but he did come up with the first effective explanation for how it happens. Describe Darwin’s theory of evolution by natural selection. Explain how this theory was a major advance over prior ideas as to how organisms changed over time. Give evidence in support of evolution and describe the driving forces for evolutionary change.
Assignment only requires 1,200 words however that isn’t an option, please write as thorough as possible in order to achieve good passing grade.
SAMPLE ANSWER
Evolution refers to the changes that occur over time on the living organisms heritable traits. The paper explores the concepts of evolution by examining Darwinian Theory of natural selection, describing the evidences that support evolution and driving forces of evolutionary changes.
Darwinian Theory of natural selection
Charles Darwin suddenly changed previous biology concept from his predecessors upside down when he published origin of species in 1859. Although there is some misconception that Charles Darwin came forth with the theory of evolution, a history is indicated that the raw materials used to develop Darwin’s theory have existed for decades. For instance, Aristotle, Lamarck and others had established evolution theory based on their observation and speculation. Lamarck for instance believed that life begun from simple single celled to form complex ones. Lamarck also described that the driving force of evolution was the need for an organism to have traits that will enable them survive in new environments. Therefore, the rate at which an organism use or does not use its body parts makes it remain or diminish over long period of time (Simon, Dickey, Reece, & Hogan, 2016).
According to Lamarck’s theory of use and disuse, the birds strong beaks was cumulative effects of evolution from their ancestors for using the beaks to feed, and acquired beak modifications was passed to their off spring. However, these explanations could not be indicated by the evidence of inheritance of acquired traits. For instance, a carpenter who gains muscular strength due to the nature of his work does not pass the enhanced muscles to their offspring. Despite the fact that Lamarck’s idea of evolution was incorrect, his idea that animals evolve due to interactive effects between the environments and organism set the platform for subsequent evolution theories (Darwin, n.d.).
Similar to Lamarck’s observation, Darwin noted that living species were descendants of ancestral organisms that were slightly different from the present day living organisms. The Darwinian ideas on evolution came into limelight in 1859 when he published the aforementioned influential books. In his book, he presented that species that exist today descended from ancestral species that were different from the existing ones. He called the process as “descent with modification.” This phrase captured the fact of shared descent and diversity. Second concept of Darwin theory of evolution is the process of natural selection (Simon et al., 2016).
According to this theory, organisms that have the best heritable traits that suit the environment tends to survive and have the largest number of offspring’s. The traits that enhance survival are passed into the offspring and are presented in large numbers in the next generation. This phenomenon of unequal reproductive success is what Darwin called as natural selection because the environment ‘selects’ only specific heritable traits from the population. Therefore, natural selection does not promote the organism’s changes but rather serves as a process of editing the products of changes that have occurred. Natural selection products are the accumulation of adaptive traits over time. An example of adaptive traits is the change of fur color in bears. The brown fur of brown bears and white fur of polar bears is an indicator of natural selection processes. Probably, the selection favored the fur color that gave each bear an appearance that is of advantage within its environment (Simon et al., 2016).
Another example of natural selection is the finches’ bird (kind of bird from Galapagos Islands). Over two decades, the researchers worked on these birds where they measured the beak size in a population of finch birds that feed on small sized seeds. Their findings indicated that birds that had large and stronger beaks had a feeding advantage and had greater reproductive success during dry seasons. During wet seasons, the small seeds gets abundant, that made the small size beaks to increase over the generations. Another example of natural selection is that of peppered moths and industrial Melanism. Before industrialization, the population of Biston betularia consisted mainly of the light colored moths. The environment was devoid of pollution which made the moths to camouflage effectively. In the next two centuries, industrial revolution occurred which made the region to be heavily polluted with soot. The light colored moths could not hide effectively on the polluted environment, which resulted in increased population of melanic individuals (Simon et al., 2016).
The world we live today has many examples of natural selection such as the development of antibiotic resistance. For instance, repeated exposure to the same antibiotics reduces bacterial susceptibility by random chance. Some of the bacteria are affected by the antibiotics and eventually die, while a small population survives. The population that survives has the potential to reproduce, giving rise to new populations that are likely to inherit the new modified traits so as to enhance their survival. In the next subsequent generations, the resistant bacteria thrive in greater numbers. Natural selection phenomenon gave rise to artificial selection. Artificial selection is the purposeful breeding of domesticated living organisms by human beings. The plants and animal products we feed on today have little resemblance to the wild types. This is evidence even in pets we live with in our homes. For instance, it is the power of selective breeding that we have saint Bernards and basset hounds dog breeds (Smith, 2011).
Evidence in support of evolution
Since Darwin’s first proposal about natural selection and evolution, different disciplines of science have produced sufficient evidence of biological evolution through natural selection. To start with, comparative anatomy indicates that living organism have a common ancestry. There are some similarities in the anatomical structures of different organisms (Darwin, n.d.). For instance, the forelimbs of the vertebrates such as cats, whales, and bats have same skeletal elements. The slight difference observed is influenced by the different functions of the limb. These structures are referred to as homologous structures- features that are structurally similar due to common ancestry but have different functions (Simon et al., 2016).
Similar observations are echoed in comparative embryology. Embryology is the study of how human being develops. For instance, during the first weeks of human development, the human embryo has gill slits such as fish. Later, the human embryos have long bony tail- a vestigial organ that becomes the coccyx in adult hood. The human fetuses also have lanugo (fine fur) at fifth month of development. These developmental anatomical similarities strongly indicate a common ancestral. The presence of vestigial structures in many organisms is also an indicator of common ancestry. For instance, human beings have a set of muscles for wiggling around their ears just as coyote. Human beings also have appendix that seems to have degenerated from cecum, where in other animals such as herbivores acts as storage for cellulose. The comparison of these vestigial organs reveals a common ancestry (Simon et al., 2016).
The study of fossil imprints of the past organism show some clues that the evolution of past living organisms. This is facilitated by radioisotope dating where scientists calculate the rates of decay of the chemical elements from the fossil. Recent advancement in molecular biology also indicates that human beings have a common ancestry. Comparison of DNA of various species provides adequate support for evolution processes. The study of DNA from the fossils indicates some similarity of distant related species. The biochemistry of living thing on earth indicates that the living organisms have a common ancestry. For instance, all nucleic acids (RNA and DNA), proteins and bio-molecules in all organisms reveal some commonality. The slight difference in associated with modification processes such as mutations that led to formation of the new sequences specific to the new functions (Simon et al., 2016).
Driving forces of evolutionary change
The main driving forces of evolutionary change are mutation, natural selection, genetic drift, and mating structure of the populations. Despite the fact that the each force will be discussed separately, it is important to note that the forces do not operate distinctly or differently from each other. The evolutionary changes are sum total effects of the interactions between these forces (Kull, 2013).
Natural selection phenomenon was brought forth by Charles Darwin. It is defined as a differential reproduction of species as a function of favorable heritable traits that enable them adapt to the environment. The special components of natural selection include a) differential reproduction, b) heritable traits and c) adaptation that lead to evolutionary changes. Mutation refers to the random heritable change of a chromosome due to alterations of the DNA sequences. The random changes can be of benefit, have neutral effects or deleterious. Deleterious mutations will be wiped out by natural selection. For instance, mutations that made houseflies’ resistance to DDT pesticide reduced their growth rate. This was a challenge to the flies that had these mutations. However, once DDT pesticide was introduced to the environment, the mutant alleles was beneficial and led to increase of their frequency through natural selection. Research indicates that chromosomal mutations that re-arrange, disrupt or delete the gene loci have deleterious effect as compared to duplication of genes through meisois(Simon et al., 2016).
Gene flow refers to the process of exchanging genetic materials between two populations. It is well evident when two population mix genes. This is commonly found in organisms that have random sexual reproduction which introduces genetic shuffling. It can lead to combination of genes that are favor natural selection, or are wiped out by natural selection. Genetic drift is the random changes of allele frequency in one generation to the next. In this force, some individuals may leave a few descendants by chance than other populations. The next population genes of the small population will consists of genes survives the natural selection and mutation forces. It is important to note that these forces occur to all populations, there is no strategies that can help living organism avoid the nature’s vagaries (Kull, 2013).
Conclusion
Natural selection is an important aspect as it promotes the evolutionary changes. Mutation is the main source of genetic variation, which is enhanced by sexual reproduction and natural selection. Like most people, I have always been confused about evolution, how it works and its relevance in the modern society. However, this study has been an eye opener on the importance of conservations efforts geared towards protecting the endangered species. Most people believe that protecting endangered species is just conserving the large number of species as possible, but studying evolution enables one to recognize that the real issue is protecting the genetic variability.
References
Darwin, C. (n.d.). On the origin of species by means of natural selection, or the preservation of favored races in the struggle for life (1st ed.). Champaign, Ill.: Project Gutenberg.
Kull, K. (2013). Adaptive evolution without natural selection. Biological Journal Of The Linnean Society, 112(2), 287-294. doi.org/10.1111/bij.12124
Simon, E. J., Dickey, J. L., Reece, J. B., Hogan, K. A. (1–2015). Campbell Essential Biology with Physiology, 5th Edition. [South University]. Retrieved from https://digitalbookshelf.southuniversity.edu/#/books/1323125574/
Smith, C. (2011). Natural selection: A concept in need of some evolution?. Complexity, 17(3), 8-17. doi.org/10.1002/cplx.20387
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