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Mar 28, 2015

Darwin and Natural Selection

Link:http://anthro.palomar.edu/evolve/evolve_2.htm
For original visit above link

Darwin and Natural Selection

Most educated people in Europe and the Americas during the 19th century had their first full exposure to the concept of evolution through the writings of Charles Darwin click this icon to hear the name pronounced.  Clearly, he did not invent the idea.  That happened long before he was born.  However, he carried out the necessary research to conclusively document that evolution has occurred and then made the idea acceptable for scientists and the general public.  This was not easy since the idea of evolution had been strongly associated with radical scientific and political views coming out of post-revolutionary France.  These ideas were widely considered to be a threat to the established social and political order.

Picture of Charles Darwin portrait at age 7

Charles Darwin at age 7
Charles Darwin was born into a moderately wealthy family in Shrewsbury, England.  His father, Robert, had the largest medical practice outside of London at the time and his mother, Susannah Wedgwood, was from a family of wealthy pottery manufacturers.  She died when Charles was only 8 years old.  Thereafter, he was raised mostly by his father and doting older sisters.  Charles grew up in comparative luxury in a large house with servants.  However, this was a socially conservative time in England that set narrow limits on a young man's behavior and future possibilities.  The constraints on women in Darwin's social class were even greater.  Most were given only enough education to efficiently manage the homes of their future husbands and raise their children.  Young men were expected to go to university in order to prepare themselves to become medical doctors, military officers, or clerics in the Church of England.  Most other occupations were considered somewhat unsavory.
At his father's direction, Charles Darwin started university at 16 in Edinburgh, Scotland as a medical student.  He showed little academic interest in medicine and was revolted by the brutality of surgery being performed without pain relief.  Anesthesia was not used for operations until 1842.  Darwin dropped out of medical school after two years of study in 1827.  However, his knowledge of natural history was incidentally enriched in Edinburgh by the teaching of Robert Grant, a noted professor of anatomy and an avid marine biologist.  At Grant's suggestion, Darwin also became a member of Plinian Society for student naturalists at the University of Edinburgh.
Having given up on a medicine as a future career, Charles Darwin's father then sent him to Cambridge University in 1828 to pursue an ordinary degreeprogram with the goal of later becoming an Anglican parson.  In Cambridge his life's direction continued its radical change.  He became very interested in the scientific ideas of the geologist Adam Sedgwick and the naturalist John Henslow with whom he spent considerable time collecting specimens from the countryside around the university.  At this time in his life, Darwin apparently rejected the concept of biological evolution, just as his mentors Sedgwick and Henslow did.  However, Darwin had been exposed to the ideas of Lamarck about evolution earlier while he was a student in Edinburgh.
Picture of a portrait of Charles Darwin in his 20's
Photo of Captain Robert Fitzroy in civilian clothes Captain Robert Firzroy 1805-1865
Charles Darwin
1809-1882


Following graduation from Cambridge in 1831 with a Bachelor of Arts degree, Darwin was clearly more interested in biology and geology than he was in a clerical career.  Fortunately, John Henslow was able to help him secure a berth on a British Navy mapping expedition that was going around the world on what would ultimately become a nearly five year long voyage.  Initially, Darwin's father refused to allow him to go but was eventually persuaded by Charles and even agreed to pay for his passage and for that of his man servant on the journey.  They sailed two days after Christmas in 1831 aboard the survey ship H.M.S. Beagle with Darwin acting as an unpaid naturalist and gentleman companion for the aristocratic captain, Robert Fitzroy.  Darwin was 22 years old at the time, and Fitzroy was only 4 years older.  The Beagle was a compact 90 foot long ship with a crew of 74.  There was little space, even for the captain.  Darwin shared a cramped 10 X 11 foot cabin with two other men, a cabin boy, and their belongings.  Because of the Beagle's design and small size, it was generally thought by naval men that it was ill suited for the rough seas it would encounter, especially at the southern tip of South America.  Darwin frequently suffered from sea sickness on the voyage.  Fortunately, he was able to spend most of the time on land exploring.  In fact, he was at sea for only 18 months during the nearly 5 years of the expedition.
Captain Fitzroy was interested in advancing science and was especially drawn to geology.  He had a surprisingly good library of over 400 books onboard the Beagle that he made available to Darwin.  It was during the beginning of the voyage that Darwin read the first volumes of Charles Lyell's "Principles of Geology" and became convinced by his proof that uniformitarianism provided the correct understanding of the earth's geological history.  This intellectual preparation, along with his research on the voyage, was critical in leading Darwin to later accept evolution.  Especially important was his 5 weeks long visit to the Galápagos Islands click this icon to hear the preceding term pronounced in the Eastern Pacific Ocean.  It was there that he made the observations that eventually led him to comprehend what causes plants and animals to evolve, but he apparently did not clearly formulate his views on this until 1837.  At the time he left the Galápagos Islands, he apparently still believed in a traditional Biblical creation of all life forms.
Picture of HMS Beagle, from an 1841 watercolor

map highlighting the route of H.M.S. Beagle in its around the world expedition--Britain to Brazil, Argentina, Chile, Galapagos Islands, New Zealand, Australia, South Africa, Brazil, and finally back to Britain

H.M.S. Beagle
(90.3 ft long, 24.5 ft. wide)
Five year voyage of H.M.S. Beagle (1831-1836)



click this icon to hear the following audio interview  Darwin's Beagle Diary
audio recording of excerpts from Darwin's popular account of his voyage of exploration.  This link takes you to an external website. To return here, you must click the "back" button on your   browser program.     (length = 68 mins, 19 secs)

The Galápagos Islands have species found in no other part of the world, though similar ones exist on the west coast of South America.  Darwin was struck by the fact that the birds were slightly different from one island to another.  He realized that the key to why this difference existed was connected with the fact that the various species live in different kinds of environments.
Map of Galápagos Islands in relationship to South America 600 miles to the east
On returning to England, Darwin and an ornithologist associate identified 13 species of finches that he had collected on the Galápagos Islands.  This was puzzling since he knew of only one species of this bird on the mainland of South America, nearly 600 miles to the east, where they had all presumably originated.  He observed that the Galápagos species differed from each other in beak size and shape.  He also noted that the beak varieties were associated with diets based on different foods.  He concluded that when the original South American finches reached the islands, they dispersed to different environments where they had to adapt to different conditions.  Over many generations, they changed anatomically in ways that allowed them to get enough food and survive to reproduce.  This observation was verified by intensive field research in the last quarter of the 20th century.
drawings showing heads of four of the Darwin finch species highlighting the differences in their beaks

click this icon in order to see the following video  Galapágos Creatures--some of the unusual animals that Darwin
        saw on the Galapágos islands.  Video clip from "Evolution:
        Constant Change and Common Threads".  (Howard Hughes
        Medical Institute, 2005)               (length = 24 secs.)
Finches from the Galápagos Islands

Today we use the term adaptive radiation to refer to this sort of branching evolution in which different populations of a species become reproductively isolated from each other by adapting to different ecological niches click this icon to hear the preceding term pronounced and eventually become separate species.
diagram illustrating the adaptive radiation of descendent species from a common ancestor              
Darwin came to understand that any population consists of individuals that are all slightly different from one another.  Those individuals having a variation that gives them an advantage in staying alive long enough to successfully reproduce are the ones that pass on their traits more frequently to the next generation.  Subsequently, their traits become more common and the population evolves.  Darwin called this "descent with modification."
The Galápagos finches provide an excellent example of this process.  Among the birds that ended up in arid environments, the ones with beaks better suited for eating cactus got more food.  As a result, they were in better condition to mate.  Similarly, those with beak shapes that were better suited to getting nectar from flowers or eating hard seeds in other environments were at an advantage there.  In a very real sense, nature selected the best adapted varieties to survive and to reproduce.  This process has come to be known as natural selection.
painting of Thomas Malthus

Thomas Malthus 
(1766-1834)  

Darwin did not believe that the environment was producing the variation within the finch populations.  He correctly thought that the variation already existed and that nature just selected for the most suitable beak shape and against less useful ones.  By the late 1860's, Darwin came to describe this process as the "survival of the fittest."   This is very different from Lamarck's incorrect idea that the environment altered the shape of individuals and that these acquired changes were then inherited.
Nineteenth century critics of Darwin thought that he had misinterpreted the Galápagos finch data.  They said that God had created the 13 different species as they are and that no evolution in beak shape has ever occurred.  It was difficult to conclusively refute such counter arguments at that time.  However, extensive field research since the early 1970's has proven Darwin to be correct.
In 1798, Thomas Malthus click this icon to hear the name pronounced, an English clergyman and pioneer economist, published Essay on the Principles of Population.  In it he observed that human populations will double every 25 years unless they are kept in check by limits in food supply.  In 1838, Darwin read Malthus' essay and came to realize that all plant and animal populations have this same potential to rapidly increase their numbers unless they are constantly kept in check by predators, diseases, and limitations in food, water, and other resources that are essential for survival.  This fact was key to his understanding of the process of natural selection.  Darwin realized that the most fit individuals in a population are the ones that are least likely to die of starvation and, therefore, are most likely to pass on their traits to the next generation.
click this icon in order to see the following video  Who Was Charles Darwin?--video clip from PBS 2001 series Evolution
        requires RealPlayer to view         (length = 6 mins, 26 secs)




An example of evolution resulting from natural selection was discovered among "peppered" moths living near English industrial cities.  These insects have varieties that vary in wing and body coloration from light to dark.  During the 19th century, sooty smoke from coal burning furnaces killed the lichen on trees and darkened the bark.  When moths landed on these trees and other blackened surfaces, the dark colored ones were harder to spot by birds who ate them and, subsequently, they more often lived long enough to reproduce.  Over generations, the environment continued to favor darker moths.  As a result, they progressively became more common.  By 1895, 98% of the moths in the vicinity of English cities like Manchester were mostly black.  Since the 1950's, air pollution controls have significantly reduced the amount of heavy particulate air pollutants reaching the trees, buildings, and other objects in the environment.   As a result, lichen has grown back, making trees lighter in color.  In addition, once blackened buildings were cleaned making them lighter in color.  Now, natural selection favors lighter moth varieties so they have become the most common.  This trend has been well documented by field studies undertaken between 1959 and 1995 by Sir Cyril Clarke from the University of Liverpool.  The same pattern of moth wing color evolutionary change in response to increased and later decreased air pollution has been carefully documented by other researchers for the countryside around Detroit, Michigan.  While it is abundantly clear that there has been an evolution in peppered moth coloration due to the advantage of camouflage over the last two centuries, it is important to keep in mind that this story of natural selection in action is incomplete.  There may have been additional natural selection factors involved.
drawing of dark and light colored peppered moths on a tree with dark colored bark and a tree with light bark
  Dark moths on light colored bark are
  easy targets for hungry birds but are
  hidden on pollution darkened trees.

click this icon in order to see the following video  The Making of the Fittest: Natural Selection and Adaptation--an example of natural
        selection in mice.  This link takes you to a video at an external website.  To return
        here, you must select this page again.           (length = 10 mins, 25 secs) 
click this icon in order to see the following video  Evolution in Action--an example of natural selection among salamanders in California
        
This link takes you to a video at an external website.  To return here, you must select
        this page again.           (length = 3 mins, 20 secs) 
click this icon in order to see the following video  Toxic Newts--the evolutionary arms race between predator and prey driving evolution
        
This link takes you to a video at an external website.  To return here, you must select
        this page again.           (length = 5 mins, 28 secs) 




Darwin's use of the phrase "survival of the fittest" is frequently misunderstood.  Many people assume that "the fittest" refers to the strongest, biggest, or smartest and most cunning individuals.  This may or may not be the case.  From an evolutionary perspective, the fittest individuals are simply the ones who have the combination of traits that allow them to survive and produce more offspring that in turn survive to reproduce.  In fact, they may be relatively weak, small, and not particularly intelligent.  What makes an individual fit all depends on the environment at the time and the combination of traits that are most suited to flourishing in it.  In the case of Darwin's finches, specialized beaks provided the advantage.  However, in a changing environment, it is often the versatile generalist who has the greatest success.
Darwin did not believe that evolution follows a predetermined direction or that it has an inevitable goal.  His explanation that evolution occurs as a result of natural selection implied that chance plays a major role.  He understood that it is a matter of luck whether any individuals in a population have variations that will allow them to survive and reproduce.  If no such variations exist, the population rapidly goes extinct because it cannot adapt to a changing environment.  Unlike Lamarck, Darwin did not believe that evolution inevitably produces more complex life forms and that the ultimate result of this process is humans.  These were shocking, revolutionary ideas even for scientists who accepted evolution.
Darwin did not rush his ideas about evolution and natural selection into print.  He first concentrated his efforts on writing the account of his around the world voyage on the Beagle and analyzing the many preserved animal and plant specimens and extensive notes that he brought back with him.  This occupied him for more than 10 years.  An additional factor that may have held him back from publishing his ideas about evolution was the widespread Christian evangelical fervor in England during the 1830's and 1840's.  He could have been charged with sedition and blasphemy for widely publishing his unpopular theory. 
After returning from the voyage of the Beagle, Darwin settled down in England, married Emma Wedgwood (his wealthy first cousin), raised a large family, and quietly continued his research at his newly purchased country home 16 miles south of London.  In 1842 he wrote a 35 page summary of his theory about evolution.  This was expanded to a 230 page manuscript in 1844, but it was not published and apparently was only known to a few people in British scientific circles.  Darwin busied himself over the next two decades establishing his reputation as an important naturalist by growing and studying orchids, pigeons, earthworms, and other organisms at his home.  He spent 8 of these years studying and writing about barnacles that people had sent him from around the world.
Picture of a portrait of Emma Darwin as a young woman

Photograph of Down House from the back garden

photo of Charles Darwin in late middle age
Emma Darwin
1808-1896
 

    Down House--Charles and Emma Darwin's country
    home where he wrote his major publications and  
    their family lived contentedly for 40 years.
Charles Darwin
1809-1882
 
It was not until he was 50 years old, in 1859, that Darwin finally published his theory of evolution in full for his fellow scientists and for the public at large.  He did so in a 490 page book entitled On the Origin of Species.  It was very popular and controversial from the outset.  The first edition came out on November 24, 1859 and sold out on that day.  It went through six editions by 1872.  The ideas presented in this book were expanded with examples in fifteen additional scientific books that Darwin published over the next two decades.
http://anthro.palomar.edu/evolve/images/Wallace.jpg

Alfred Wallace
1823-1913

What finally convinced Darwin that he should publish his theory in a book for the general educated public was the draft of an essay that he received in the summer of 1858 from a younger British naturalist named Alfred Wallace click this icon to hear the name pronounced, who was then hard at work collecting biological specimens in Southeast Asia for sale to museums and private collectors.  Darwin was surprised to read that Wallace had come upon essentially the same explanation for evolution.  Being a fair man, Darwin insisted that Wallace also get credit for the natural selection theory during debates over its validity that occurred at a meeting of the British Association for the Advancement of Science at Oxford University in 1860.  We now know that Darwin deserves most of the credit.  In 1837, one year after he returned from the voyage on the Beagle, he made detailed notes on the idea of evolution by means of natural selection.  At that time, Wallace was only 14 years old.  In addition, it was Darwin's book, rather than Wallace's essay, that had the most impact on the Victorian public.  Darwin not only described the process of natural selection in more detail, but he also gave numerous examples of it.  It was his On the Origin of Species that convinced most scientists and other educated people in the late 19th century that life forms do change through time.  This prepared the public for the acceptance of earlier human species and of a world much older than 6000 years. 
click this icon to hear the following audio interview  Darwin and Victorian Culture--interview with Darwin's biographer, James Moore
       This link takes you to an audio file at an external website.  To return here, you must click
       the "back" button on your browser program.           (length = 8 mins, 5 secs)


http://anthro.palomar.edu/evolve/images/Mendel.jpg

Gregor Mendel
1822-1884
Both Darwin and Wallace failed to understand an important aspect of natural selection.  They realized that plant and animal populations are composed of individuals that vary from each other in physical form.  They also understood that nature selects from the existing varieties those traits that are most suited to their environment.  If natural selection were the only process occurring, each generation should have less variation until all members of a population are essentially identical, or clones of each other.  That does not happen.  Each new generation has new variations.  Darwin was aware of this fact, but he did not understand what caused the variation.  The first person to begin to grasp why this happens was an obscure Central European monk named Gregor Mendelclick this icon to hear the name pronounced.  Through plant breeding experiments carried out between 1856 and 1863, he discovered that there is a recombination of parental traits in offspring.  Sadly, Darwin and most other 19th century biologists never knew of Mendel and his research.  It was not until the beginning of the 20th century that Mendel's pioneer research into genetic inheritance was rediscovered.  This was long after his death.   He never received the public acclaim that was eventually showered on Darwin during his lifetime.
Charles Darwin's convincing evidence that evolution occurs was very threatening to many Christians who believed that people were created specially by God and that they have not changed biologically since that creation.  The idea that there could have been prehistoric humans who were anatomically different from us was rejected for similar reasons.  However, Charles Lyell's geological evidence that the earth must be much older than 6,000 years along with the rapidly accumulating fossil record of past evolution convinced educated lay people in the 1860's to think what had been unthinkable earlier.

painting of Boucher de Perthes in 1832
Boucher de Perthes 
1788-1868  
Archaeological confirmation of the existence of prehistoric Europeans had been accumulating since the 1830's.  However, until the late 1850's, it had been widely rejected or misinterpreted.  Much of this evidence had been collected by Jacques Boucher Crèvecoeur de Perthes click this icon to hear the name pronounced, a customs officer in northern France during the early 1800's.  His hobby was collecting ancient stone tools from deep down in the Somme River gravel deposits.  Since he found these artifacts in association with the bones of extinct animals, he concluded that they must have been made at the time that those animals lived.

19th century drawing of a well shaped prehistoric hand ax in front and side views

Prehistoric artifact incorrectly thought
to be a "lightning bolt remnant"
  
Boucher de Perthes tried to publish his findings in 1838.  They were rejected by all important scientists and scientific journals.  The prehistoric stone tools usually were dismissed as being only "lightning stones" (i.e., the remnants of lightning bolts).  However, by 1858, his claims were beginning to be accepted by some enlightened Western European scientists.  Darwin's publication of On the Origin of Species the following year convinced even more educated people that Boucher de Perthes had been right.
Darwin's popularizing the idea of evolution also made it possible for scientists to begin to accept that some of the makers of Boucher de Perthes' prehistoric tools had already been discovered and that their bones were in museums.  These bones had been found in several Western European countries during the first half of the 19th century.  However, they had all been dismissed as being from odd looking modern people.  During the 1860's, some were correctly determined to be from an earlier species or variety of people who had lived during the last ice age--i.e., long before recorded history.  We now know that these ancient people were mostly Neandertals, who lived about 150,000-28,000 years ago.


NOTE:   Charles Darwin was an active collector of plant and animal specimens and a prodigious note taker on the voyage of H.M.S. Beagle.  By the time the ship returned to England in 1836, he had accumulated 5,436 plant and animal specimens that had been dried or preserved in alcohol.  He had 368 pages of notes on plants and animals as well as 1,383 pages of geological observations.  In addition, he had a 770 page diary that was the basis for his later popular book of his narrative on the voyage ("Journal of Researches Into the Natural History and Geology of the Countries Visited During the Voyage of H.M.S. Beagle Round the World, Under the Command of Capt. Fitz Roy, R.N.").
NOTE:   From the time that Charles Darwin published "On the Origin of Species" in 1859 on up to the present, the presumptions of many people led them to misread the title.  They assumed that it was "On the Origin of the Species".  The implication of inadvertently adding "the" is that his book was about human evolution.  In fact, that was not the case, though it had implications for human evolution.  It focused on non-human animals and the mechanisms of evolution.  He did not pointedly address the question of human evolution until the publication of his 1871 book "Descent of Man and Selection in Relation to Sex".
NOTE:   The phrase "survival of the fittest" was apparently first used in 1851 by the influential British philosopher Herbert Spencer (1820-1903) as a central tenet of what later became known as "Social Darwinism."  He misapplied Darwin's idea of natural selection to justify European domination and colonization of much of the rest of the world.  Social Darwinism was also widely used to defend the unequal distribution of wealth and power in Europe and North America at the time.  Poor and politically powerless people were thought to have been failures in the natural competition for survival.  Subsequently, helping them was seen as a waste of time and counter to nature.  From this perspective, rich and powerful people did not need to feel ashamed of their advantages because their success was proof that they were the most fit in this competition.  Despite misgivings by Alfred Wallace and other naturalists, Charles Darwin began to use "survival of the fittest" as a synonym for "natural selection" in the 5th edition of Origin of Species, which was published in 1869.
NOTE:   H.M.S. Beagle, the famous ship that took Charles Darwin on his 1831-1836 voyage around the world, had a rather mundane history following her return to England.  She was transferred by the British Navy to the Customs and Excise Department and was used to catch smugglers along the southeast coast of England.  The Beagle was finally sold for scrap in 1870 after 50 years of service.

Mar 24, 2015

Survival Of The Fittest Philosophy Essay: Darwin

Link:ukessays.com/essays/philosophy/survival-of-the-fittest-philosophy-essay.php

For original: Visit above link

Survival Of The Fittest Philosophy Essay

In the current essay we will review the survival of the fitters, different issues and theories connected with it. Survival of the Fittest – is the aphorism, introduced by Herbert Spencer and Darwin said in “Origin of Species” (1859) as the main factor of the theory of natural selection. This theory states: (A) reproduction in any species implies a certain degree of natural variations in results; (B) Any change that increases the survival ability of some members of the species with respect to the other, deprived of such changes could positively selected for reproduction capabilities; (C) the millennia, this process led to the development of complex organisms from simple and to the great diversification of the small number of initial organisms. The concept of "survival of the fittest" in sociology has described a few cases of apparent consumption, except for Social Darwinism. 
The chapter on natural selection overrides Darwin from that point on is: "Natural Selection, or The Survival of the Fittest." Darwin was forced to take this step, since his work "On the Origin of Species by Means of Natural Selection" directly exposed to allegations of massive appearance was in 1859, with the term "Natural Selection" is personified nature, as described in Charles Darwin Quotes: Scientific Theory. The decisive argument for the expanded terminology provided then Darwin's supporters Alfred Russel Wallace, who wrote to Darwin, the term "Natural Selection", which is actually a metaphorical expression for Herbert Spencer's "Survival of the Fittest." "Natural Selection" is therefore inappropriate, as in the evolution is not so much a beneficiary selection, rather than an elimination of unfavorable individuals occur. Darwin agreed with this criticism and took over the term. 
"Fit" or "fitness" describes in Darwin's sense of the level of adaptation to the environment (the adaptive specialization), or the reproductive capacity despite low specialization, and not the physical strength and ability in terms of direct competitive displacement with the use of force. That is not the kind of live that defies all repressed and other species, but one which adapts to either the environment or manages to proliferate continuously in spite of adverse environmental conditions. On the criticality, the ambiguity and the potential for abuse of Spencer's terminology - even in the original English language -. Darwin and Thomas Henry Huxley associate at an early stage of the discussion have indicated. Evolutionary biologists today avoid the term because its current idea of evolution does not adequately describe it. First, it suggests continuity in the evolution toward ever greater “fitness”. Today's species would then be "fitter" than extinct, which is not the case. Secondly, it ignores the principle of sexual selection.
Herbert Spencer coined the term "Survival of the Fittest" in 1864 in his Principles of Biology" and brought him to the debate about Darwin's book on the origin of species: 
“If ... Individuals of a species ... necessary in countless directions and degrees differ, must ... then have to be always less exposed than some other of the risk among all individuals and that their balance by a special force acting ... would be completely destroyed. ... The inevitable result will be that those individuals whose functions differ most from the equilibrium with the modified aggregate external forces must be destroyed, while the other hand, will live those who are their functions closest to the equilibrium with the modified sets of external forces near.” This survival of the fittest ... is the same as what Mr. Darwin understood as natural selection." Sometimes, represented in the history of science literature view, Spencer had coined the "Survival of the Fittest" already in 1851 in his "Social Statics" or 1852 in his "Theory of population", which is not correct in this form, as stated by Charles Darwin. Spencer took the concept here but not the term for the "Survival of the Fittest" in a political-sociological sense. The term "Survival of the Fittest", he brought only in 1864 as described above in the "Principles of Biology" in the debate over Darwin's Origin of Species, as described in Charles Darwin’s The Origin of Species.
Generally speaking, "fittest" in the "fittest" is the inventor of the Spencer coined as a result of this struggle for the survival of individuals, in Darwin's natural selection theory is naturally defined for each individual - the focus on being adaptable. You can directly observe the individual organism for which natural selection acts, whether a significant impact on survival is certainly lucky. The survival of the fittest takes place thousands of years – is a period of tens of thousands of years, "a generational change in mean thousands" are expected.  Creationists such as the objections to evolution "is a survivor of the fittest, the fittest survive," say the claim cycle theory (or a tautology, tautology), and science are not to argue. However, this expression is a metaphor for a brief description of the mechanism, the theory does not prove anything. Biologists generally not use this expression, called natural selection. And natural selection is supported by the fact that the observed field work and experiments. 
The idea that species can change under the action of selection, different scholars have repeatedly expressed since ancient times, including some English writers beginning of the XIX century. However, widespread acceptance of the concept of natural selection was once in 1858 by British scientist Charles Darwin and Alfred Wallace presented in his articles published in the same issue of the Journal of the Proceedings of the Linnean Society of London. Zoology, the idea that wildlife is a mechanism, similar to artificial selection, and especially after the publication in 1859 of Darwin's Origin of Species. Sense of their idea is that the emergence of successful creation of nature is not necessarily to understand and analyze the situation and can act at random. It is enough to create a wide variety of animals - and, ultimately, the fittest will survive. Currently, some naive views of Darwin himself turned out to be partially redesigned.Thus, Darwin imagined that the change should happen very smoothly, and the range of variation is continuous, as described in Darwin's Theory Of Evolution. Today, however, the mechanisms of natural selection are explained by genetics, makes for some originality in this sense. Mutations in the genes that operate at the first stage of the process described above, are discrete changes in the genotype. Clearly, however, that the basic meaning of Darwin's ideas remained unchanged. 
There are different classifications of forms of selection. Widely is used classification that is based on the nature of the effect of forms of selection on the variability of the trait in the population. Driving the selection - a form of natural selection, which operates in the directed change of environmental conditions, as described by Darwin and Wallace. In this case, individuals with symptoms that are deflected in a direction from the average, receive benefits. In this case, different variations of feature (its deviation in the opposite direction from the mean) are subjected to negative selection. As a result, in a population from generation to generation, a shift of the average character in a certain direction. The pressure driving the selection must meet the adaptive capabilities of the population and the rate of mutational change (otherwise the pressure of the environment can lead to extinction). 
Stabilizing selection - a form of natural selection, in which his action is directed against individuals with extreme deviations from the average, in favor of individuals with an average severity of the trait. There are described many examples of stabilizing selection in nature. For example, at first glance it seems that the greatest contribution to the gene pool of the next generation must make the individuals with the highest fertility. However, observations of natural populations of birds and mammals show that it is not that way. Selection in favor of mean values was found in a variety of symptoms. In mammals, newborns with very low and very high weight more likely to die at birth or during the first weeks of life than babies of average weight, as described in Darwin's Quotes: Not Survival of the Fittest? 
Disruptive (tearing) selection – is a form of natural selection, where conditions are conducive to two or more extreme options (directions) of variation, but not conducive to an intermediate, average trait. As a result, you may receive several new forms from a single source. Darwin described the action of disruptive selection, considering that it lies at the heart of the divergence, though he could not give evidence of its existence in nature. Disruptive selection contributes to the emergence and maintenance of polymorphism in populations, and in some cases can cause speciation. 
One of the possible situations in nature, which comes into effect disruptive selection – is when the polymorphic population is heterogeneous habitat. The different forms are adapted to different ecological niches or subnishes. 
Survival of organisms is important, but not the only component of natural selection exists. Another important component is attractive to individuals of the opposite sex. Darwin called this phenomenon of sexual selection: "This form of selection is determined not by the struggle for existence in the relations of organic beings to each other or with external conditions, but the rivalry between individuals of one sex, usually males, for the possession of individuals of the opposite sex." Sexual selection is a natural selection for success in breeding. Features that reduce the viability of their carriers, may occur and spread, if the benefits that they provide a breeding success is much higher than their weaknesses to survive. It was suggested that there are two main hypotheses about the mechanisms of sexual selection. According to the hypothesis of "good genes" and female "reasons" as follows: "If the male, despite its bright plumage and long tail, somehow managed not to die at the hands of predators and survive to sexual maturity, then, consequently, he has good genes, which allowed him to do it. Hence, he should be chosen as a father to his children: he will give them his good genes." Choosing bright males, females choose good genes for their offspring, as described by Michael Heeney.
According to the hypothesis of "attractive sons," the logic of the choice of females is somewhat different. If males are bright, for whatever reasons, they are attractive to females, you should choose a bright future for your sons, because sons will inherit the genes of bright colors and will be attractive to females in the next generation. Thus, a positive feedback loop that leads to the fact that generation after generation of bright plumage of males is increasingly growing. The process goes on increasing until it reaches the limit of viability. In the choice of mating females is no more and no less logical than the rest of their behavior. When the animal feels thirsty, it is not a reason for him to drink water in order to restore fluid and electrolyte balance in the body – he is going to drink because he feels thirsty. Likewise, the females choose bright males, they follow their instincts - they like the bright tails. All those who instinct other behavior, all they have left no progeny. Thus, we have not discussed the logic of the females, and the logic of the struggle for existence and natural selection – is a blind and automatic process, which, acting continuously from generation to generation, and formed all the amazing variety of shapes, colors and instincts, which we observe in the world of wildlife . 
Positive selection - a form of natural selection. Its effect is the opposite of truncation selection. Positive selection increases the number of individuals in the population, with useful features that increase the viability of the species as a whole. Truncation selection – is a form of natural selection. Its effect is the opposite of positive selection. Truncation selection is discarded from the population, the vast majority of individuals carrying signs, dramatically reduce the viability under these environmental conditions. 
Survival of the fittest is in terms of species and populations, such as species having gills in the water, because fit can win the fight for survival. There are survival bodied organisms, survival of the physically strongest of organisms as physical struggle for resources is an integral part of life. Survival of the most sexually successful organisms happens because sexual reproduction is the dominant mode of reproduction. In this case, it takes sexual selection. However, all these cases are private, but mostly remains successful preservation time. So sometimes these areas are violated for the sake of following the main goal, as stated in Survival of the fittest. 
Charles Darwin believed that natural selection is a fundamental factor in the evolution of life. Accumulation in the late XIX - early XX century, information on genetics, in particular the discovery of the discrete nature of the inheritance of phenotypic traits, prompted many researchers to revise the thesis of Darwin: as critical factors of evolution were considered mutation genotype. On the other hand, the discovery of the known correlations among the traits of related species led to the formulation of hypotheses about the evolution on the basis of laws and not random variability. Discussion of the role of various factors in the evolution continues today, and evolutionary biology came to the need for his next, the third synthesis. As a dact, Darwin long hesitated to publish his theory, as seen the problem of ants, which can be explained only in terms of genetics, as stated in Survival of the fittest.
Survival of the fittest is the main driving force of evolution of living organisms. Thinking about the existence of natural selection came independently and almost simultaneously to several English naturalists: V. Wells (1813), P. Mathews (1831), E. Blythe (1835, 1837), A. Wallace (1858), Darwin (1858, 1859), but only Darwin was able to discover the significance of this phenomenon as the main factor of evolution and created the theory of natural selection. Unlike human- artificial selection, natural selection is due to effects on organisms of the environment. According to Darwin, natural selection - is "the experience of the fittest" organisms, which resulted on the basis of uncertain genetic variation in the number of generations takes evolution. 
In general, we can say that natural selection is daily and hourly throughout the world investigating minute changes, rejecting the bad, preserving and pondered them good, working silently and invisibly, wherever and whenever they are neither presented in this case, on the improvement of each organic being in connection with the conditions of his life, organic and inorganic. Man does not see these slowly make changes in their movement forward and time to just ignore diversity of contemporary forms of life once existed. 
Although natural selection can only operate for the benefit of the organism and the only effect of this benefit, however the signs and structures, which seem to be quite insignificant, may enter into the terms of the selection process. When the insects that feed on leaves, green, and eating the bark - spotty - gray, alpine ptarmigan white in winter, and the red grouse is painted the color of heather, we must assume that these stains are beneficial to these birds and insects, protecting them from danger. Considering these differences between species that seem insignificant, one must not forget that they are directly influenced by climate, food, etc. Also, the force of law correlations should be noted that when one part varies and changes accumulate by natural selection, there are other changes, often the most unexpected properties, as described in Survival of the fittest. 
If the changes that occur under domestication, in a certain period of life, tend to occur in the offspring in the same period - even in the natural state, natural selection will act on the organisms and modify them at any age through favorable changes in this age group and by their inheritance in the corresponding same age. Natural selection may modify and adapt the larva of an insect to numerous conditions, quite different from those in which the adult insect lives, and these changes in the force of law correlations may impact on the adult form. Similarly, and vice versa: changes in adult insects may affect the structure of the larvae, but in any case, natural selection will ensure their safety, because otherwise having them exposed to the extinction of species. Natural selection changes the structure of relatively young parents and parents that are relatively young. In social animals, it adapts the structure of each individual to the needs of the community, if only to make the community benefit from this change in the selection of exposed individuals. 
In order to clarify the action of natural selection, it is sufficient to provide one or two imaginary examples. Let us consider the example of the wolf, feeding on different animals and one beset by force, and other tricks, the third-speed, imagine that the fastest prey, deer, for example, have increased in number by which any changes that have occurred in the area, or whether another production decreased in particular, just at the time of year when wolves suffer the most from lack of food. In such circumstances, the fastest and lean wolves will have a better chance to survive and, thus, remain or be selected. You can give another more complicated example, illustrating the mode of action of natural selection. Insects in search of nectar and pollen will crumble very often will move her from flower to flower. So by going to cross between the flowers, belonging to two different individuals, and this process will give rise to cross over the mighty seedlings, consequently will have the best chance for prosperity and survival. Plants that produce flowers with the nectaries, select the largest amount of nectar, insects will visit more often and more frequently subjected to cross-breeding and, eventually, will overcome their rivals, and form a local variety. One can imagine another case: insects visiting the flowers to collect nectar is not, and pollen, and as pollen is used exclusively for fertilization, then its destruction should be, it would seem to bring only damage to the plant, however, if a little pollen, first accidentally and then permanently tolerated eating insects pollen from flower to flower, and this would be achieved by cross-breeding, at least nine-tenths of the pollen being destroyed, this kind of robbery would be quite beneficial to plants, and individuals that produce more and more pollen and fitted with larger anthers, would be subjected to selection. Thus, the examples can be seen in the fact that natural selection operates only through the preservation and accumulation of small inherited modifications, each of which is advantageous for saving the creatures. 
Much of the variability, of course, and individual differences are likely to be a favorable circumstance. A large number of individuals are increasing the chances of a given period of useful changes, can compensate for a lesser degree of variation in individual animal and it is an important element of success. Hybridization plays an important role in nature, as it supports uniformity and consistency traits in individuals of the same species or same species.  Length of time in itself does not promote or impede natural selection. The length of time is important, as it increases the chances of favorable changes in their selection, accumulation and retention. 
Extinction is caused by natural selection. This issue should be mentioned because of its close connection with natural selection. Natural selection acts only through the changes, in some sense useful, and therefore root. Because of the rapid increase in the number of all organic beings exponentially, each area is already filled to the limit of the inhabitants, and from this it follows that, as the favored form will increase in number, the less favorable treatment will usually decrease in numbers and become rare. The rarity of forms – is a forerunner of extinction. Any form submitted by a small number of individuals has a better chance at the final extinction, due to a significant climatic fluctuations during the year or due to a temporary increase in the number of its enemies. Species, most wealthy individuals, have the greatest chance for the appearance at any given period of favorable changes. Hence, rare species at any given time will change and evolve more slowly and therefore will be defeated in the battle of life change and improve the descendants of the more common species. From this it follows that, since over time the activities of natural selection, the formation of new species, while others have become increasingly rare, finally disappear. 
Sometimes it is difficult to explain the people’s behavior, as people hurt one another, which, for example, you will never see among animals. You don't see wild animals killing animals of the same species, yet people do it all the time. Often people behave in a strange way, and the laws of “animal kingdom” do not apply. Also, prisoners and people on life support can be compared, as the examples of the consequences of the survival of the fittest. Nature has its laws and sometimes people can not control them. True that people have discovered many types of medicine that help people to survive and often save lives. The survival of the fittest can now be controlled in some way.
Nature has its rhythm and whatever people do does not change a lot in the world, as nature is more powerful than we think. Some people survive, some people die, but the tendency is that the number of people is constantly growing. However, some people believe that the laws of nature determine everything. It can be said that the Earth is a living organism and people can not interfere in its life. Some people and philosophers even think that people do not have to cure each other, as there is the survival of the fittest that determines everything.
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