Evolution

In this article, “Descent with Modification: a Darwinian View of life”, Biology, 2005, N.A, Campbell, J.B. Reece explain how Darwin came up with his view of life and present the main points of his theory of evolution.

According to the authors, Darwin’s early ideas came from his travelling of five years through the world.(1831-1836) on the Beagle. The ship that he used was to explore the South American coastline. On this ship, he visited jungles, pampas, and grassland of South America. He spent most of time collecting and observing samples of animals, plants and fossils. Some of the fossils belong to ocean which found in mountain, this evidence can show earth He found that the fauna and flora of South America were similar to each other despite climatic differences, but different from Europe. Darwin stopped at the Galapagos Island; he found many species (finches) live nowhere else in the world. Then he began to think the life is influenced by environment.

From the above observations, the authors point out that new species are the result of evolution which Darwin called “descent with modification”. According to Darwin, as species had to adapt to their environment, some of their traits changed. Beaks of finches from Galapagos Islands, they can change their beaks for picking their food just in short period time and one generation. One species in two different environments can have different changes that depend on the environment, so all life forms are related to previous forms, according to Darwin. He used image of a tree to explain the history of life. The tree has multiple branches from a common trunk to the tips of the youngest twigs such as species of life in the present. A good example would be Asian elephants and African elephants. They look similar because they share the same line of descent until a relatively recent divergence from their common ancestors. About 99% branches are extinct, that’s why we can’t see the middle of their generation. Darwin perceived an important connection between natural selection: “struggle for existence” and the capacity of organisms to over reproduce”. Only the strongest survived and reproduce because they are the best adapted to their environments.

The chapter concludes with summary of natural selection, we know Darwin was able to observant how natural selection is working only in few generations. In nowadays, Artificial Selection is humans modify other species over many generations by selecting and breading individuals that make them change their traits. At the end of this article, the authors gave three important points about evolution by natural selection that many students often misunderstand. First one is overproduction of populations, individual do not evolve. That means the individual can’t evolve himself. The second one is heritable variations, means the good traits and genetic mutations transfer to the next generation, and only genetic modifications can be passed on, not acquired ones. The third one is environment factors, every species are influenced by environment. One generation affect by environment, but they may not change it immediately, this year’s positive adaptor would be next year’s negative one.
So, in the authors’ opinion, according to Darwin’s evolution, life changes very slowly, if there is enough time to let life change, entire diversity of life will be changed by environment.