Evolution Paper Assignment

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Evolution Paper
Evolution according to Collins dictionary means gradual change in the characteristics of living things over successive generations, especially to a more complex form. My definition, evolution is gradual development, expansion, maturation or progress of life in different ways. Science defines evolution as the process by which species of organisms arise from earlier life forms and undergo change overtime through natural selection.
The modern understanding of the origins of species is based on Greenberger (11) theories on Charles Darwin combined with a modern knowledge of genetics based on the work Gregory Mendel (Edelson 51). Evolutionary processes give rise to diversity at every level of biological organization, including species, individual organisms and molecules such as DNA and proteins. Heritable traits are known to be passed from one generation to the next via DNA, a molecule that encodes genetic information. DNA is a long polymer composed of four types of bases.
The sequence of bases along a particular DNA molecule specifies the genetic information, in a manner similar to a sequence of letters spelling out a sentence. Before a cell divides, the DNA is copied, so that each of the resulting two cells will inherit the DNA sequence. Portions of a DNA molecule that specify a single functional unit are called genes; different genes have different sequences of bases (Virgilio 123). Within cells, the long strands of DNA form condensed structures called chromosomes. The specific location of a DNA sequence within a chromosome is known as a locus. If the DNA sequence at a locus varies between individuals, the different forms of this sequence are called alleles. DNA sequences can change through mutations, producing new alleles. If a mutation occurs within a gene, the new allele may affect the trait that the gene controls, altering the phenotype of the organism (Durrett 5).
However, while this simple correspondence between an allele and a trait works in some cases, most traits are more complex and are controlled by multiple interacting genes. Recent findings have confirmed important examples of heritable changes that cannot be explained by changes to the sequence of nucleotides in the DNA (Durrett 8). These phenomena are classed as epigenetic inheritance systems. DNA methylation marking chromatin, self-sustaining metabolic loops, gene silencing by DNA interference and the three dimensional conformation of proteins (such as prions) are areas where epigenetic inheritance systems have been discovered at the organismic level.
Developmental biologists suggest that complex interactions in genetic networks and communication among cells can lead to heritable variations that may underlay some of the mechanics in developmental plasticity and canalization. Heritability may also occur at even larger scales. For example, ecological inheritance through the process of niche construction is defined by the regular and repeated activities of organisms in their environment. This generates a legacy of effects that modify and feed back into the selection regime of subsequent generations. Descendants inherit genes plus environmental characteristics generated by the ecological actions of ancestors. Other examples of heritability in evolution that are not under the direct control of genes include the inheritance of cultural traits and symbiogenesis. For example, salmon trying to make it upriver to spawn before a hot summer hits, slow and steady loses the evolutionary race. Many species have changed their migration patterns over the past few decades in response to warmer and comfortable temperatures for laying their eggs. Salmon DNA records stretching back over 30 years show that nature has increasingly selected for fish that migrate from the ocean earlier in the year.
It is among the first pieces of genetic evidence that climate change is driving the evolution of a species. What is difficult to tell is whether the species are changing their behavior or evolving genetically - or both (Brener 161). An old experiment, researchers at the University of Alaska at Fairbanks were able to confirm that genes play a role in at least one animal's response to warmer temperatures - the pink salmon. Its migration from the ocean to the river is controlled largely by its genes.
In the 1970s, Anthony Gharrett was studying why some salmon migrate up Alaska's Auke Creek a month later than the rest of the population (Reardon Para 3). Gharrett selectively bred some late-migrating fish so t...