Sunday, March 7, 2010

Components of Evolution

Coyne's book is obviously about him proving why he believes evolution is true. Before stating whether or not evolution is true, he must first define what he believes evolution is. He first mentions his definition of evolution on page 3 and says that evolution consists of 6 main components. What are the six main components of evolution? Define each component as well as how they relate to one another (Hint: Coyne refers to two of the components as "flip sides of the same coin," on page 4).


  1. Coyne defines evolution as having six main parts. These parts consist of evolution, gradualism, speciation, common ancestry, natural selection, and nonselective mechanisms. Evolution is when a species undergoes genetic change over time. DNA changes over time due to mutations in a species genome. Not all species evolve at the same rate however. The second part of evolution is gradualism; gradualism explains that evolution occurs over thousands of years, and it does not always happen at an even pace. Evolution can be more rapid when natural selection is strong or a species is colonizing a new environment. Evolution slows down as the species becomes more adapted to its environment, and it is more stable. It is also important to recognize that the planet is diverse with multiple groups of species. This is possible due to speciation. All species go back to a single common ancestor. This is proven due to the fact that all species share four common fundamental traits: the biochemical pathways used to produce energy, four-letter DNA code, the way in which DNA is read and translated into proteins. Speciation means that a single species split into two completely different species that cannot interbreed or exchange genes. This happens as a single species lives in different places, and their differences gradually grow large enough to prevent them from having the ability to interbreed. Not all species split though because some will die off and won't leave any descendants. Every time a species splits, it doubles the number of opportunities for future speciation. All species closely related share a common ancestor. This is shown by all species that exist within the vertebrates. Fish, amphibians, mammals, and reptiles all have a backbone and are all vertebrates. Therefore, they must have descended from a common ancestor that also have backbone. Within vertebrates, reptiles and mammals are united separate from fish and amphibians for having an amniotic egg; they must have had a more recent common ancestor that possessed this egg to allow them to be related. Mammals and reptiles are different however due to the fact that mammals are warm blooded, have hair, and produce milk, as opposed to reptiles that are cold blooded, are scaly, and produce watertight eggs.

  2. Natural selection is also another key part to the theory of evolution. Natural selection explains that individuals in a species that have certain genes that help them to survive better in their environment will be more likely to pass on their genes to the next generation. This next generation will have more of these good genes, which lead to higher survival and reproduction chances. The population overtime will become better suited to the environment as mutations arise and spread throughout. The wooly mammoth that lived in northern parts of Eurasia and North America was well adapted to the cold environment due to its thick hair. The mammoth probably evolved from an ancestor with less hair, and as the climate grew cold, the individuals with more hair were better suited to the environment and were able to survive and pass on their genes for more hair. As time went on, the number of individuals with more hair increased and the mammoth grew hairier. Other features that also helped an individual better survive in the cold could also have affected the mammoth genome, which would have allowed it to survive better in its environment. Mutations allow individuals to adapt to their environment; however, mutations do not create brand new features that an individual never had before. A new species is created from its previous ancestors. Natural selection creates fitter species, but it does not create perfection. Evolution does not only occur through natural selection however. This is the final point of evolutionary theory. Nonselective mechanisms besides natural selection can also create evolutionary changes in a species. Random changes in the proportion of genes occurs as different families have different numbers of offspring. Genetic drift can also play a small role in smaller populations because it probably accounts for some non-adaptive features of DNA. If evolution is true, then through the means of both natural selection and nonselective mechanisms, the genome of individuals in a species can be mutated to allow an individual to adapt to its environment and gradually change into a new species that cannot interbreed with its previous ancestors.