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Beavers build a dam to create a pond suitable to sustain them and raise young. New forms will then invade the range of their ancestral species. Fisher studied the effect of natural selection on large populations. This trait did not vary continuously. Occasionally, a mutation would arise natural selection essay allowed its bearer to reproduce better than its contemporaries.



Darwin exhibit in at the American Museum of Natural History. Screenshot from exhibit web site. Its best-known exponent was English theologian William Paley, creator of the famous watchmaker analogy. If we find a pocket watch in a field, Paley wrote in , we immediately infer that it was produced not by natural processes acting blindly but by a designing human intellect.

Likewise, he reasoned, the natural world contains abundant evidence of a supernatural creator. The argument from design, as it is known, prevailed as an explanation of the natural world until the publication of the Origin of Species in In some circles, however, opposition to the concept of evolution has persisted to the present. These antievolutionists differ from fundamentalist creationists in that they accept that some species do change but not much and that Earth is much more than 6, years old.

Like their predecessors, however, they reject the idea that evolution accounts for the array of species we see today, and they seek to have their concept—known as intelligent design—included in the science curriculum of schools. ID is getting a hearing in some political and educational circles. Most biologists have concluded that the proponents of intelligent design display either ignorance or deliberate misrepresentation of evolutionary science.

Yet their proposals are getting a hearing in some political and educational circles and are currently the subject of a debate within the Ohio Board of Education. The section concludes with an overview of the intelligent-design movement by a philosopher and cultural historian who has monitored its history for more than a decade. The Challenge of Irreducible Complexity: Every living cell contains many ultrasophisticated molecular machines.

Intelligent Design position statement By Michael J. To Charles Darwin and his contemporaries, the living cell was a black box because its fundamental mechanisms were completely obscure.

We now know that, far from being formed from a kind of simple, uniform protoplasm as many nineteenth-century scientists believed , every living cell contains many ultrasophisticated molecular machines.

Does natural selection account for complexity that exits at the molecular level? How can we decide whether Darwinian natural selection can account for the amazing complexity that exists at the molecular level?

Some systems seem very difficult to form by such successive modifications—I call them irreducibly complex. An everyday example of an irreducibly complex system is the humble mousetrap. It consists of 1 a flat wooden platform or base; 2 a metal hammer, which crushes the mouse; 3 a spring with extended ends to power the hammer; 4 a catch that releases the spring; and 5 a metal bar that connects to the catch and holds the hammer back.

All the pieces have to be in place before you catch any mice. Natural selection can only choose among systems that are already working so irreducibly complex biological systems pose a powerful challenge to Darwinian theory. Irreducibly complex systems appear very unlikely to be produced by numerous, successive, slight modifications of prior systems, because any precursor that was missing a crucial part could not function.

Natural selection can only choose among systems that are already working, so the existence in nature of irreducibly complex biological systems poses a powerful challenge to Darwinian theory. We frequently observe such systems in cell organelles, in which the removal of one element would cause the whole system to cease functioning.

The flagella of bacteria are a good example. They are outboard motors that bacterial cells can use for self-propulsion. They have a long, whiplike propeller that is rotated by a molecular motor.

The propeller is attached to the motor by a universal joint. The motor is held in place by proteins that act as a stator. Other proteins act as bushing material to allow the driveshaft to penetrate the bacterial membrane. Dozens of different kinds of proteins are necessary for a working flagellum. In the absence of almost any of them, the flagellum does not work or cannot even be built by the cell.

Constant, regulated traffic flow in cells is an example of a complex, irreducible system. Another example of irreducible complexity is the system that allows proteins to reach the appropriate subcellular compartments. In the eukaryotic cell there are a number of places where specialized tasks, such as digestion of nutrients and excretion of wastes, take place.

This constant, regulated traffic flow in the cell comprises another remarkably complex, irreducible system. All parts must function in synchrony or the system breaks down.

Still another example is the exquisitely coordinated mechanism that causes blood to clot. Molecular machines are designed. Biochemistry textbooks and journal articles describe the workings of some of the many living molecular machines within our cells, but they offer very little information about how these systems supposedly evolved by natural selection.

Many scientists frankly admit their bewilderment about how they may have originated, but refuse to entertain the obvious hypothesis: Advances in science provide new reasons for recognizing design.

I am hopeful that the scientific community will eventually admit the possibility of intelligent design, even if that acceptance is discreet and muted. My reason for optimism is the advance of science itself, which almost every day uncovers new intricacies in nature, fresh reasons for recognizing the design inherent in life and the universe.

Intelligent design fails the biochemistry test. Evolution response to Michael J. Behe By Kenneth R. Behe fails to provide biochemical evidence for intelligent design. To understand why the scientific community has been unimpressed by attempts to resurrect the so-called argument from design, one need look no further than Michael J. He argues that complex biochemical systems could not possibly have been produced by evolution because they possess a quality he calls irreducible complexity.

Just like mousetraps, these systems cannot function unless each of their parts is in place. And if such systems could not have evolved, they must have been designed. Parts of a supposedly irreducibly complex machine may have different, but still useful, functions.

Take away two parts the catch and the metal bar , and you may not have a mousetrap but you do have a three-part machine that makes a fully functional tie clip or paper clip. Take away the spring, and you have a two-part key chain. The catch of some mousetraps could be used as a fishhook, and the wooden base as a paperweight; useful applications of other parts include everything from toothpicks to nutcrackers and clipboard holders.

The point, which science has long understood, is that bits and pieces of supposedly irreducibly complex machines may have different — but still useful — functions. Evolution produces complex biochemical machines. Evolution produces complex biochemical machines by copying, modifying, and combining proteins previously used for other functions. Although the function performed by this small part when working alone is different, it nonetheless can be favored by natural selection. The blood clotting system is an example of evolution.

The key proteins that clot blood fit this pattern, too. The elegant work of Russell Doolittle has shown how evolution duplicated, retargeted, and modified these proteins to produce the vertebrate blood-clotting system. Working researchers see evolution in subcellular systems. And Behe may throw up his hands and say that he cannot imagine how the components that move proteins between subcellular compartments could have evolved, but scientists actually working on such systems completely disagree.

In a article in the journal Cell, a group led by James Rothman, of the Sloan-Kettering Institute, described the remarkable simplicity and uniformity of these mechanisms. If Behe wishes to suggest that the intricacies of nature, life, and the universe reveal a world of meaning and purpose consistent with a divine intelligence, his point is philosophical, not scientific.

It is a philosophical point of view, incidentally, that I share. However, to support that view, one should not find it necessary to pretend that we know less than we really do about the evolution of living systems.

In the final analysis, the biochemical hypothesis of intelligent design fails not because the scientific community is closed to it but rather for the most basic of reasons — because it is overwhelmingly contradicted by the scientific evidence. Detecting Design in the Natural Sciences: Intelligence leaves behind a characteristic signature.

Intelligent Design position statement By William A. Dembski Chance, necessity, or design covers every eventuality in ordinary life. In ordinary life, explanations that invoke chance, necessity, or design cover every eventuality. Nevertheless, in the natural sciences one of these modes of explanation is considered superfluous — namely, design. From the perspective of the natural sciences, design, as the action of an intelligent agent, is not a fundamental creative force in nature.

Does nature require no help from a designing intelligence? But how do we know that nature requires no help from a designing intelligence? Certainly, in special sciences ranging from forensics to archaeology to SETI the Search for Extraterrestrial Intelligence , appeal to a designing intelligence is indispensable. Essential to all these techniques is the ability to eliminate chance and necessity.

Complex, sequenced patterns exhibit intelligence in their design. The researchers run signals through computers that are programmed to recognize many preset patterns. Prime numbers, of course, are those that are divisible only by themselves and by one. When a sequence begins with 2 beats, then a pause, 3 beats, then a pause… and continues all the way to beats, the researchers must infer the presence of an extraterrestrial intelligence. If a sequence lacks complexity, it could easily happen by chance.

The sequence is therefore contingent rather than necessary. Also, it is a long sequence and therefore complex. Note that if the sequence lacked complexity, it could easily have happened by chance. Finally, it was not just complex but also exhibited an independently given pattern or specification it was not just any old sequence of numbers but a mathematically significant one — the prime numbers.

Note that complexity in the sense of improbability is not sufficient to eliminate chance: Specifications must be objectively given. The important thing about specifications is that they be objectively given and not just imposed on events after the fact.

Undirected natural processes are incapable of generating the specified complexity in organisms. In my book The Design Inference, I argue that specified complexity reliably detects design.



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