Comparison of DNA and protein sequences only makes sense in light of evolution. Our understanding of infectious organisms and our tactics to combat them are entirely based upon understanding of evolution. No idea comes from thin air. The historical perspective helps to understand where the concepts behind evolutionary theory came from. Here are some of the basic historical issues. The typical view of the nature of species at the beginning of the nineteenth century is often described as the Doctrine of Fixed Species.
This concept had its primary roots in Greek philosophy: During the eighteenth century, Carolus Linnaeus developed the basis for our nested, hierarchical classification system, or Taxonomy. The geologic discipline of stratigraphy was developed during the late eighteenth and early nineteenth centuries.
Though this accomplishment was shared by many geologists throughout Europe, the name most commonly associated with developing the concept of stratigraphy is William Smith , who was an engineer engaged in building canals all over England.
George Cuvier eventually Baron George Cuvier was a scientist of the late 18th and early 19th centuries. His specialty was vertebrate anatomy. Because of his expertise in anatomy, Cuvier was the obvious person to ask to examine strange remains found during reconstruction after a major Paris fire.
These remains turned out to belong to extinct organisms, and led to the development of the field of study we call Paleontology. Cuvier was the first to reconstruct dinosaurs. Cuvier is also remembered for coming up with the concept of Catastrophism, as an attempt to reconcile his religious beliefs with the evidence he discovered as a scientist. Charles Lyell , a British geologist, developed the concept of Uniformitarianism. In other words, the forces acting upon and shaping the Earth today are the same as the forces that acted upon and shaped the Earth in the past.
Uniformitarianism is a central tenet of modern geology. Darwin was born in the first century of the nineteenth century to a wealthy family. His hobby was natural history.
He collected beetles, went on geological field trips and became very friendly with the natural history faculty at his universities. During the five-year trip, he collected tons literally of specimens of animals, plants and fossils, which he shipped back to England for later analysis. Upon returning to England, he officially became a naturalist. Almost all of his specimens were sent to experts for analysis.
He kept the barnacles for himself, setting out to become an expert in barnacles. It was the analyses that were returned to him from his experts that started him thinking along revolutionary pathways. Thus, in order for humans to continue to survive, some have to die. One reason he finally published in and then published Origin of Species in was that he discovered that another man, Alfred Russell Wallace , had independently discovered and was about to publish exactly the same theory Darwin had been working on for 20 years.
Darwin saw a clear pattern of common descent among the species of life. Examining the expert analyses of all of the specimens from the Beagle expedition, it was clear to Darwin that the various forms of life were all descended from one, or many from a very few, common ancestral species.
The mechanism Darwin figured out by which species could change from one thing into something different was natural selection. He saw environmental competition as providing the selective pressure in nature. All living things tend to over-reproduce.
There will be competition over resources, and not all members of any generation can survive. Many aspects of variation are heritable, meaning that they are passed from parents to offspring. Each new generation will tend to be more like the successful parents and less like the unsuccessful parents. Given enough time meaning enough generations , these changes can produce brand new species, especially if the environmental pressure is strong.
What is the evidence in support of the theory of evolution? This question could take weeks to answer. Observations of a wide variety of phenomena demonstrate evolutionary action and consequences. Here are some examples:. Adaptive radiation, which Darwin saw abundantly demonstrated among the species he observed and collected while on the Beagle. Adaptive radiation is the phenomenon in which a single species splinters into many daughter species.
This phenomenon is very commonly observed among species living on off-shore islands like the Galapagos Islands to the west of South America. The fossil record abundantly demonstrates evolutionary change.
Transitional sequences show, for instance, the emergence of mammals from reptiles in the Permian Period, and the emergence of Cetaceans from terrestrial mammals in the early Cenozoic Era.
Biogeography the distribution of species geographically abundantly supports evolution, specifically island biogeography, which shows us that the resident species of islands are always derived from the species on the adjacent mainland.
These are the questions man has been asking for thousands of years. It has only been recently, however, that science was sophisticated enough for us to be able to approach the real answer.
Anyone can tell you that the currently accepted explanation is the Theory of Evolution. In the early to mid s, the Theory of Evolution was being formed in the minds of many scientists, but it was first given voice by Charles Darwin in his Origin of Species. He proposed that a process called natural selection acts on random variation within a species to cause only the most fit of that species to survive and leave fertile offspring.
Natural Selection is a process that "chooses" specific individuals based on their characteristics, by allowing them to survive and multiply, whereas less suited individuals die out. Thus, over time, only those organisms most suited to their particular environment survive, and organisms become more and more specialized and sophisticated.
Darwin's theory was widely hailed at the time of its publication as being an excellent explanation for the diversity of living things on our planet, and as time has passed, it has only gained more acceptance.
Generally, the only opposition to the theory came from religious circles, who insisted that the world was created in six days and all the animals and plants were created exactly as we see them. While many in the public clung to their beliefs, this obviously did not have much support from the scientific community.
After all, there is very little evidence for such a creation, and there is plentiful evidence for evolution. However, in more recent times, other, more legitimate challenges to the Theory of Evolution have surfaced. This, then, is the goal of my paper: To outline the principle problems with the theory of evolution, the answers presented by the scientific community, and to evaluate the validity of the Theory based on these questions and answers.
During Darwin's lifetime, there was a great deal that science did not know, could not know, about the inner workings and mechanisms of life. Cells themselves had been discovered, but that was about the most anyone could find out about until the invention of the electron microscope, followed by even more advanced devices for detecting things on a microscopic level. The discoveries that have surfaced as a result of this technology has both helped and hindered Darwin?
On the one hand, we know much about DNA, the all-important molecule that is the blueprint for the body, and is passed down from generation to generation. It is this inheritance, and the variability of the genetic sequences, that allows for how natural selection acting on variation could actually work. Further, once you allow for the all too frequent advent of mutations in genes, Darwin? On the other hand, this wealth of new information makes us privy to so many complex mechanisms of such an unbelievably fine, elegant construction, many that would have had to exist before that actual origin of life in itself, that one finds it hard to fully believe the Theory of Evolution can have a place today.
The Darwinian concept is not one of large jumps, such as, say, having nothing one day and a perfectly functioning eyeball the next, but rather of small steps.
If there is a gene that codes for a finger, slight alterations to this gene should allow for a somewhat longer finger. Forelimbs that are flatter and therefore more suited to swimming in a marine creature can become more flat with successive generations. In the billions of years during which life has existed, surely there would be enough time for the development of all the various features we see around us.
There are two large problems with this way of seeing things. The first is that for so many different variations of life to have developed, there would have to be a lot more intermediary life-forms. Granted the less suitable organisms would have eventually died off, but certainly there should at least be some sort of fossil record of all these intermediate creatures.
There is a large and extensive fossil record, but the gaps between more primitive and more advanced forms are very large, and few, if any, intermediates have been found. This is a great puzzle to science. Drs Elliot and Gould theorized one possible answer, now known as the theory of Punctuated Equilibrium. This theory states that evolution takes place in a cycle consisting of a long period of little evolution followed by a relatively short period of much change and evolution, probably caused by large changes in an environment, such as the onset of an ice age or the death of a very large amount of organisms and species, thus clearing much evolutionary space.
By this theory, since the intermediate periods would be so relatively short, the chances of an adequate fossil being preserved are very small, which explains why we don? The problems with this theory abound. What reason is there for such evolution to occur at this time more than at any other? Richard Dawkins suggests that perhaps there is a gene that causes an increase in mutation rates, but since as a whole this sort of mechanism would tend to be detrimental rather than helpful to most organisms, and it as yet has not been discovered in any case, this would certainly be a very weak foundation upon which to rest a theory.
The other large problem modern science has with evolution is that the simple process of elongating an already existing organ structure would require more than just a simple change in one gene. Take, for example, the lengthening of a finger:
- Charles Darwin’s theory and evolution Introduction: Charles Darwin was an English scientist who developed the theory of evolution which had been around for long period of time which gave him fame during his life and after his death.
We Can Write a Custom Essay on Darwin's Theory of Evolution for You! Darwin's theory was widely hailed at the time of its publication as being an excellent explanation for the diversity of living things on our planet, and as time .
Charles Darwin proposed the theory of evolution to explain the origin, diversity and complexity of life. I will will disprove evolution by showing that natural selection only explains small evolutionary changes, collectively known as microevolution. Natural selection cannot drive large evolutionary changes, macroevolution. This free Science essay on Essay: Evolution and Charles Darwin is perfect for Science students to use as an example. What is the modern status of Darwin’s theory of evolution? A. All of the basic concepts have remained sound, and have survived extensive challenge and testing. There was a great deal of evidence in support of Darwin.
Essay on Charles Darwin's Theory of Evolution by Natural Selection - When the name Charles Darwin is uttered, an immediate association brings about the concept of Evolution. Although he was not the first to "discover" this phenomenon, he . Charles Darwin in his theory of evolution suggests that man evolved from ape-like creatures. In this theory, there is an indication that the early man was distinct from apes.