Natural Selection Essay Research Paper In suggesting

Natural Selection Essay, Research Paper

In suggesting the process of natural selection as the means resulting in evolution, Charles Darwin shows how evolutionary changes have occurred in organisms. Genetic change through time Understanding natural selection is paramount to our comprehension of evolution. is a much more accepted than the theory man has evolved from apes. Despite the fact that we are unable to prove without a shadow of doubt that man has evolved from apes, natural selection is relevant to the changes that have occurred over the years in humans.

Charles Darwin s theory of natural selection was based on two observations, first the fact that all species exhibit variability, for example height, colour, etc. Secondly all organisms than survive to reproduce. To understand why natural selection is much more acceptable than the idea of evolution from apes, we must first understand the Principles of Natural selection. The first principle of natural selection is that a species must be capable of reproduction of more than enough offspring to replace itself. Secondly, the environment may affect ones chances of survival. Third, because each individual is unique some may have more chances of survival than another. Lastly, the ability to adapt to ones environment increases ones chance for survival. After the acceptance of these principles, one can understand how change through time or evolution must have occurred in the past and continues to occur today.

The reproductive capacity of most organisms is enormous compared to the number of offspring that reach maturity in each generation. For example spiders can produce hundreds of offspring, dogs and cats produce fourteen or more offspring in a litter and human beings may produce ten or more offspring in a lifetime. It is this reproductive capability that fulfills the first of Darwin s principles. By reproducing we are continuing the life cycle allowing for more of each creature to exist in the future. It is the objective of each organism to try to ensure the future existence of its species through reproduction. It is this objective that explains attraction to the opposite sex and why certain traits are selected for in a mate. Although it seems the selection of a mate is random, it actually has more to do with ensuring the survival of ones gene pool than we realize. Humans select unconsciously according to what we believe to be the traits that will be selected for by nature. However, if all the offspring were to survive, the biosphere would be so crowded that eventually there would be no room for new organisms. So following the first of Darwin s principles, organisms are capable of reproduction, however the second principle keeps overcrowding from happening.

Killing thousands of people and animals each year, disasters such as flooding, tornados, earthquakes, drought, disease and infestation carry out the second of Darwin’s principles. Although it is saddening to realize that many must die in order for others to survive, this is what is referred to as survival of the fittest. It is these unforeseen disasters that are responsible for genetic drift, a process in which the genetic makeup of the population changes by chance over time instead of being shaped in a nonrandom way. The environment decides which organisms will live and die through natural disasters and those who can adapt to the changes that have occurred in the environment. Due to adaptation, organisms are able to keep from getting completely wiped out however; this does not guarantee the further existence of a species. It is important to notice that selection produces adaptations that benefit individuals. Such adaptation may or may not benefit the population or species. The species or population as a whole may not benefit because change has eliminated that breed and created a new breed that is more adapted to the requirements of the environment, for example temperature changes requiring fur verses no fur. The environment affecting ones chances of survival is not only due to natural disasters, if the environment changes the organisms in it must be capable of change as well. With out change or adaptation of the organism in a changing environment, continued existence is not possible. That is to say, a deme cannot afford to vary greatly in a stable, competitive, and hostile environment, for random variation may be lethal; the deme must remain well adapted. At the same time, the deme must be able to change, evolve, in adaptation to environmental change. This necessary genetic stability, accompanied by flexibility in the form of adaptability, is the basis of Darwinian fitness, and the balance struck between these two factors determines how fit a population is. Change for organisms is a delicate balance since survival depends on the right changes for the environment. Lack of adaptation is just as deadly to organisms as natural disasters, if not more so.

Each organism is an individual and differs from other organisms in many ways. Being diverse keeps the world interesting, but more than that it makes chances for survival unpredictable as well. It is organism s differences that can increase or decrease the probability of survival. If organisms in a niche were all white and a factory was built near the niche depositing black ashes throughout the area, the white organisms would be visible to prey and would be eaten. The only chance of survival would be