Long standing arguments against the theory of natural selection stem from the occurrence of incipient structures and complex traits in organisms despite the seemingly stochastic nature of mutations. Many complex adaptations observed in nature today are thought to have arisen from less complex ones with simpler functions, therefore these characters are thought to have been “pre-adapted.” In order to go from a simple to a complex structures there must have been a transitional phase, where the two structures function simultaneously or where the new function is assumed without interfering with the old function. These structures are termed incipient or incomplete, and given what we know to be true of natural selection and the theory of evolution it becomes hard to reconcile the idea that natural selection continued to favor these structures despite the lack of selective value. Incipient structures are thought to be neither sufficiently large enough not elaborate enough to perform an adaptive function and thus it also becomes difficult to understand how larger complex characters arise. A discussion of morphological and developmental genetics explains that these structures have been performing useful functions since their simple origins, therefore being selectively favored while at the same time evolving to become large enough to accumulate new more complex functions. Modification of pre-existing genes and regulatory circuits in early development has been extensively studied in metazoans, Hox genes and the development of complex structures such as eyes, limbs and appendages. Phenotypic variation is therefore generated via the modification of existing genes, regulatory processes and developmental processes and this variation is acted o...
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In the book, Your Inner Fish, by Neil Shubin he presents the notion of evolution and how we can trace parts that make up the human body back to jellyfish, worms, and even fish. The book not only discusses how we arose to be what we are today, but also the implications our ancestors had on our current body plan. In this essay, I will demonstrate that I have digested the entirety of Shubin’s book by convincing you (dear reader) that everything in our bodies is based on simple changes to already existing systems. To make this case, I will use the evidence of limb development in a vast array of organisms, the four arches found in the embryological stage of development, the structures inside our noses, and how our ears have come about all due to modifications.
Feder and Park present a list of traits that are used by paleoanthropologists to distinguish the appearance of skeletal features and characterize these changes over time. Th...
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Charles Darwin’s theory of natural selection explains the general laws by which any given species transforms into other varieties and species. Darwin extends the application of his theory to the entire hierarchy of classification and states that all forms of life have descended from one incredibly remote ancestor. The process of natural selection entails the divergence of character of specific varieties and the subsequent classification of once-related living forms as distinct entities on one or many levels of classification. The process occurs as a species varies slightly over the course of numerous generations. Through inheritance, natural selection preserves each variation that proves advantageous to that species in its present circumstances of living, which include its interaction with closely related species in the “struggle for existence” (Darwin 62).
Evolution is one of the most well supported theories throughout science and is one of the best explanations we have to help us understand the diversity of life forms. There are so many parts to evolution and with each of them having various explanations it is understandable that there are also numerous misconceptions surrounding the theory. Whilst when the theory of evolution was first introduced it produced a fair bit of controversy, it was widely accepted by many biologists. Despite this, it continues to be a difficult and debated topic and so misbeliefs about it largely exist. For these reasons it is important that we study evolution and begin to understand the truth behind these misconceptions.
One of the main reasons why their critique is successful is because they do not introduce too strong of an argument against adaptationism. For instance, one of the main faults that Gould and Lewontin find with the adaptationist programme is that it places too much emphasis on adaptation as the primary cause. What this does, they recognize, is it weakens the argument for adaptation so much that it is unable to withstand thought experiments that prove otherwise. Gould and Lewontin’s example of the spandrel and of the human chin demonstrates this problem very well because they both show that adaptation cannot possibly be the primary cause. By suggesting that adaptation is not the primary cause of a trait, but still recognizing that it is an important part of the evolution of organisms, they are able to reconcile adaptation with other evolutionary causes that seem more probable as the primary causes of traits.
The successful sequencing of complete genomes has provided us with a virtual map of many organisms (Zhaurova, 2008). This accomplishment should be viewed not as an end in itself, but rather as a starting point for even more research. The future promises more progress in genetics evolutionary biology and in other areas of biology, science, and technology. Armed with accumulating genomic sequences researchers are now trying to unravel some of biology's most complicated processes (NHGRI, 2011), such as uncovering the genomic events that led to the formation of early life and the development of new species (Hudson, 2008). As the complexity and sheer amount of genomic information grows so to will our understanding of the evolution of life on Earth.
Many scientists in the past, such as Aristotle and Plato, believed that there were no changes in populations; however, other scientists, such as Darwin and Wallace, arose and argued that species inherit heritable traits from common ancestors and environmental forces drives out certain heritable traits that makes the species better suited to survive or be more “fit” for that environment. Therefore, species do change over a period of time and they were able to support their theory by showing that evolution does occur. There were four basic mechanisms of evolution in their theory: mutation, migration, genetic drift, and natural selection. Natural selection is the gradual process by which heritable traits that makes it more likely for an organism to survive and successfully reproduce increases, whereas there is a decline in those who do have those beneficial heritable traits (Natural Selection). For example, there is a decrease in rain which causes a drought in the finches’ environment. The seeds in the finches’ environment would not be soft enough for the smaller and weaker beak finches to break; therefore, they cannot compete with the larger and stronger beak finches for food. The larger and stronger beak finches has a heritable trait that helps them survive and reproduce better than others for that particular environment which makes them categorized under natural selection (Freeman, 2002).
Gould, Stephen Jay. "Evolution as Fact and Theory." The Norton Mix. Editor Katie Hannah. New York: W.W. Norton & Company, 2010. 110-119.
Throughout the various phyla discussed evolutionary advancements are relevant. Starting from the basic, simplistic life forms of a sponge, up to the intelligence of an octopus and advance organ systems of Annelida the changes have only improved. Some species changed and evolved because as populations grow, they spread out farther and different conditions begin to affect their life. Why some species haven’t changed is because their body plan and system works for the environment they inhabit. Evolution has helped animals spread out all over the world and adapt to various conditions, seen in the habitats Aschelminthes can prosper in.