Evolution!
Evolution is a big subject. Full of controversy and “opinions”. Recently in our studies over evolution I have done some research on some different people who have contributed their theories to the subject of Evolution. Darwin is the philosopher that I had actually heard about...his name was familiar. Darwin had a theory that everything was related. And all life descended from a common ancestor. He believed that what an animal desired, like for example, longer trunks for an elephant to reach more food, or the changes a single organism experienced in its life had nothing to do with the evolution of the species. Darwin stated that all organisms are different, including organisms of the same species, and that those with variations in their traits that help them to survive have more offspring. And when these “varied” organisms have their offspring, they are born with the parent’s variations. And as they reproduce, most of the population is made up of individuals who share that trait. The other individuals in the species, who are not as well adapted as the others, die off. Back to the elephants for example- Most elephants had short trunks. Then when food and water became out of reach with the shorter trunks, those elephants died off. But the elephants with longer trunks continued to reproduce and soon all existing elephants had long trunks. Darwin also had the belief that evolution follows no plan. Lamarck on the other hand did believe that changes were made according to what the organism needed or wanted. Using the elephants again, Lamarck said that all elephants were short trunked and when they could no longer reach food or water they stretched their trunks. And then their offspring inherited the new long trunks. Lamarck also had the belief that the human body parts that are not being used would eventually disappear, people would no longer be born with those parts. Lamarck believed that when it came to evolution it was all set out in a predetermined plan and that all results have already been decided.
What is microevolution? Microevolution is evolution on a small scale. Basically evolution within a single species. Microevolution is focusing on one part of the tree of life basically. When I was looking through some websites I found that some of the keywords in microevolution are very important, they are the Mutation is a word that is often seen or used in our society in different media sources, like movies or books. But really what role does it play in microevolution? “Mutations are the source of new alleles, through changes in the genetic material.”1 The most common changes in genetic material are single nucleotide substitutions and gene duplications. Mutations are a very important source of novelty in micorevolution. But the observed rates of mutation are actually too low to be accounted for alone in the observed rates of microevolution in organisms. “Genetic drift is the random change of allele frequencies in small populations.”2 Genetic drift is the chance fluctuation in the frequency of the genes. Migration or gene flow also has an effect on microevolution. When organisms move to different places they take their genes with them, if their genes are different they change the evolution of the species in that area. Last but not least is Natural Selection. Natural Selection is when the organisms with a certain gene escape predation and live to reproduce faster than the organisms with a different gene. Natural Selection over time gradually eliminates inferior species. Natural Selection is Darwin’s theory, which I described above when I talked about the differences between the theories of different evolution philosophers.
Macroevolution on the other hand is evolution on a big scale. Macroevolution is what we see when we step back and look at the big picture. It focuses on the changes and stability of evolution as a whole over time. And it usually involves more than one species. It isn’t really easy to understand or see microevolutionary history or the effects considering we are looking at time spans that in some cases span billions of years. So evidence like geology, fossils, and living organisms are really helpful in seeing the history. Once we know what events concerning evolution happened we can look at how they happened. The basic evolutionary mechanisms like mutation, migration, genetic drift, and natural selection, which are also part of microevolution are present and at work in macroevolution and can help to show and explain the history of ever changing life. These mechanisms can create HUGE changes in evolution if given some time. That is what Macroevolution is, looking at those changes over time.
Biochemistry reveals the similarities between organisms that aren't in the same species. There is additional evidence that all organisms developed from a common ancestor because there are certain blood proteins found in almost every organism. Scientists have compared the universal blood proteins of some organisms. They have found evidence of the different levels of relatedness among different species. Embryology is the study of embryos, or unborn/unhatched animal or human young in the earliest phase. Embryos of many animals look quite similar. The traits found in the embryo of one organism are often found in the embryos of other organisms. One example is human and fish embryos. Both have gills. The difference is the gills on the fish continue to grow and develop, on the human being they disappear before birth. All of this shows that animals are similar and they develop similarly. This implies that they develop from a common ancestor and started out the same. Then they gradually started to develop new traits, but the basic plan for a creature's beginning stays exactly the same. Comparative Morphology involves the study of the external features of organisms. Analogous Structures and living fossils are the two evidences that Comparative Morphology reveal for evolution. Darwin used The Fossil Record to conclude that organisms just continue to get more complex. He noticed when he was studying fossils, that the older they get the less recognizable they became. They younger fossils were more like the organisms that exist today. Darwin used this as proof that organism's have not remained the same since the earth's beginning. From looking at the fossils he also found that new species arise and others go extinct.
I think Darwin and his theories are really what swayed me here when I was writing this paper. I think that the way the puts his findings together and the way he backed up everything really made sense. I believe that species have changed over time from Darwin’s theories about how the organisms with variations continued to live and reproduce which made them in the end the only living “versions” of that species. It makes sense. Almost a survival of the fittest type thing. I really understand evolution because of what I read on Darwin and his findings and I really agree with his view of the topic. Obviously evolution is very controversial and there are so many different theories and new evidence is brought out in to the open everyday. But I believe there is indeed substantial evidence from Darwin and many other theorists that support evolution.
All of the following websites helped me in completing this paper:
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Hi,
ReplyDeleteThe theme of your blog is very nice and the article is written very well, I will continue to focus on your article.
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Thanks!
Mark Holland