Evolution has explain how life has been changed over generations. These changes may involve all aspects of life, including mutation, natural selection, and genetic drift. One way to explain how evolution occurs is through natural selection. It is said that individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of their traits.
Evolution is the process of biological change by which descendants come to differ from their ancestors. The new generations are born with different inheritable traits and the traits which are superior for survival are passed on to the new generations.
The theory of evolution was developed by Charles Darwin in the mid 1800’s after many years of travelling, observation, experimentation and discussion. The theory and evidence to support his theory has changed the perception of the world and explains how species change over time and how adaptations may develop in species. Some of Darwin’s examples of how evolution occurs and why it is that organisms have features to serve specific functions are: he observed that numerous species found on one island looked different from those on nearby islands and that many of the islands species looked different from those on the nearest mainland. Also the saddle backed tortoises, which have long necks and legs and lived in areas with a lot of tall plants. While tortoises with shorter necks and legs lived in wet areas rich in mosses and short plants. His observation of numerous species of Finches in the Galapagos Islands with strong, thick beaks lived in areas with a lot of large, hard shelled nuts, while those species of finches with more delicate beaks were found where insects or fruits were widely available.
Since Darwin’s time, paleontologist have found fossils that supported the initial predictions and have supplied additional evidence and confirmation. Paleontologists have studied, recovered and also reconstructed many fossils remains of thousands of organisms that lived in the past, which shows that many kinds of extinct organism were very different in form from any modern organism that lives now. The fossil records have provided evidence to support the theory of evolution by documenting the pattern of evolution showing that past organisms differed from present-day organisms and that many species have become extinct.
Such as the discoveries of a 150-145 million year old fossil of Archaeopteryx, it had jaws with teeth and a long bony tail like dinosaurs, broad wings and feathers like birds, and skeletal features of both. This discovery verified the assumption that birds had reptilian ancestors.
Also with fossil records, it was discovered that whales evolved on land. Their last land ancestor was Indohyus which had teeth, bones, and ears that resemble the whale. Also scientific research in several different fields of biology have further supports and shows there is evidence that the modern whale species have descended from hoofed mammals; have vestigial pelvic and leg bones; small muscles devoted to external ears that no longer exist and they have DNA sequences of milk protein genes.
There are many different ways species change, but most of them can be described by the natural selection. Natural selection is the primary driving force of evolution and it is the process responsible for the evolution of adaptive features that allows species to survive, reproduce and pass these variation over to future generations.
The theory of evolution through natural selection was the first scientific theory that put together evidence of change through time as well as a mechanism for how it happens. Besides Charles Darwin, the other person who develop a theory about natural selection were Alfred Russel Wallace who also studied the huge diversity of plants and animals in the tropics. The four main principles of the Theory of natural selection are: variations, overproduction, adaptation and descent with modification.
Variation:
Every individual within a population is different from each other in some way – this shows variations. Some of these differences or variations can provide an increased chance of survival or decreased chance of survival. Some variations will provide either an advantage or disadvantage on an individual’s survival.
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Individuals that possess a favorable variation/phenotype will have an increased chance of reproducing and passing on this variation/phenotype to their offspring. Inheritance of this trait will provide the offspring an increased chance of survival and they will reproduce, passing on that variation/phenotype to the next generation. Over time and many generations, if this variation continues to provide an advantage for their survival. The individuals within the population showing the variation will increase chances of survival.
Whereas, individuals that have less favorable variations or have poorly adapted to their environment are less likely to survive and reproduce. Which means that their genes are less likely to be passed on to the next generation resulting in a decrease in the number of individuals with that particular variation within the population.
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Overproduction:
Individuals within a population are always competing each other for resources, such as food, shelter and even their mating partner. In the end, those who have a selective advantage over other individuals will be able to compete for the resource.
In many situations, there are times in which individuals do not compete for resources, but are competing so they will not be eaten by a predator or killed by a particular disease. In this case, individuals with a particular variation that reduces their chance of being eaten or killed will have a higher chance of survival. Types of variations that would benefit these situations include color variation – for camouflaging or variation in body behavior – Some animals, such as goats, freeze themselves to act as if they’re dead around predators.
Adaptation
Adaptation is a process that species go through to become fitted to its environment. For example Snakes lost their legs to fit into underground spaces, mice grew large ears to hear predators at night, and giraffes developed long necks to reach the leaves on tall trees and bend down to drink water.
Darwin explained that the organisms with more favorable variations or adaptations and with higher reproduction rates could increase their chance for survival. These species pass these adaptations to future generation, and that could help to spread their adaptations throughout the entire species.
Descent with modification
Descent with modification refers to passing on traits from parent to their offspring, and this concept is one of the fundamental ideas behind Charles Darwin’s theory of evolution. When these modifications are beneficial for survival, they can gradually become established in an entire population, by means of natural selection and other factors. In a population these modifications can result in significant differences from the initial population over many generations. Therefore many of species today do not look the same as their ancestors.
Natural selection can occur with or without environmental changes. Evolution by natural selection is dependent on traits being heritable in a population. Natural selection can cause microevolution or through genetic drift – a change in allele frequencies over time. These traits can be changed by directional selection which occurs when natural selection favors one extreme of continuous variation over other phenotypes. Over time the favored extreme will increase their chances for survival whereas the other extreme will be less common or lost. For example the white peppered moths in London at the beginning to the Industrial Revolution evolved into a dark species in order to blend in with the environment.
Stabilizing selection favors the intermediate phenotype against the extreme phenotype and becomes more common in the population. For example, the unchanging anatomy of sharks and ferns is evidence of stabilizing selection.
Disruptive selection occurs when both extreme phenotypes are favored against the intermediate phenotypes. For example when an animal has to camouflage to fit in to its environment.
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The most controversy facing evolutionary theory are some people argue that there is insufficient evidence to support the idea that species change over time. Also it is said that there is no evidence for speciation or for common descent or that speciation has never been observed. Another is mutation or genetic drift cannot be predicted. But evidence of evolution is proven by diverse sources such as geography, anatomy, embryology, medicine, chemistry and ecology.
We can safely conclude that evolution has occurred and continues to occur. All life forms, including humans, evolved from earlier species, and all still living species of organisms continue to evolve today. New technology and modern techniques such as DNA sequence analysis and molecular fingerprinting has further our understanding of evolution and provide new information about the way evolution occurs. As environment change, populations would adapt or go extinct. When a population becomes extinct, a different species can take its place and the cycle will continue. Natural selection is the only process that make populations adapted or better suited for their environment over time. Also, the success of passing on genes to the next generation will result in the continuity of life forms on earth over time.
