Week 2 - Natural_Selection_Simulation

Week 2 - Natural_Selection_Simulation - LS1 Read before...

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LS1 Read before section, bring copy to section Page 1 of 6 EVOLUTION: EXPERIMENTS USING COMPUTER SIMULATION Introduction Evolution is the process whereby populations of organisms change over time. This change occurs on small or large scales resulting in changes from modest to massive. The changes range from the development antibiotic resistance in bacteria, observable over the course of bacteria, to the diversity of life we see today, evolved over millennia. Evolution is such an integral part to so many aspects of biology, it prompted the illustrious scientist, Theodozius Dobzhansky (1900-1975), to famously remark, “Nothing in biology makes sense except in the light of evolution.” Most simply, evolution can be defined as a change in allele frequencies over time . Although the word “evolution” often evokes images of large, observable change - such as the evolution of the long neck in the giraffe – any significant change in its allele frequencies can be considered evolution. After enough time and the right conditions, these changes in allele frequency can produce morphological, physiological, or behavioral changes in the population as long as there is a genetic contribution to those traits. An individual’s genotype is its genetic constitution, the sum total of its genetic material. This genotype is translated into the phenotype of an organism, which is its physical and behavioral makeup. The phenotype is the product of their genetic makeup (genotype), development, and environmental conditions. Although the name most often associated with evolution is Charles Darwin (1809-1882), many biologists and naturalists before Darwin’s time recognized that species were not static, i.e. they evolved. Darwin’s own grandfather, Erasmus Darwin (1731-1802), a noted naturalist himself, theorized that species changed over time. Jean-Baptiste Lamarck (1744-1829) posited that morphological changes occurred over time due to the relative use or disuse of features, so that over time, evolution caused the elongation of the giraffe’s neck because they were always stretching their necks to feed on leaves high in the upper branches of trees. Charles Darwin’s theory of evolution by natural selection put forth a satisfactory mechanism explaining how these changes had occurred. Briefly summarized, the mechanism of natural selection as framed by Darwin has four key components: 1. More individuals in a population are born than survive and reproduce 2. There is inherent variation of traits in any population 3. Traits are heritable 4. Survival and reproductive success is not random . It is determined by the traits exhibited by the organism. Darwin deduced that the variation in the traits determined which individuals reproduced more than others (natural selection); and that because these traits are passed from parent
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LS1 Read before section, bring copy to section Page 2 of 6 to offspring, subsequent generations of that population would differ from their ancestors in the traits they possessed (evolution).
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