Given that a species diverged from its ancestor 80 million years ago, which of the following graphs most likely illustrates the pattern of mutation accumulation in the genome of this species over time?

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Quizplus · Accepted Answer

11ecba2d_1014_dca3_a3bf_f1a2af528a9f_MD0008_00 According to the neutral theory of molecular evolution, most genetic mutations are neutral and do not affect the fitness (reproductive success) of an organism. Genetic drift leads to the random fixation or loss of neutral mutations; ultimately, however, these neutral mutations accumulate at a fairly constant rate in a species over evolutionary time. This accumulation of neutral mutations in the homologous DNA of species is said to be linear and is referred to as a "molecular clock." The molecular clock model allows researchers to measure evolutionary time and estimate the evolutionary relationships between species by analyzing the rate of neutral mutations in the genome. The species described above diverged from its ancestor 80 million years ago and, according to the molecular clock model, it has likely been accumulating mutations across this entire span of time. Therefore, the overall number of mutations should increase linearly over evolutionary time; only the graph in Choice C shows this linear increase in mutations over time. (Choices A, B, and D) Because the increase in neutral mutations is linear over time, the species described should have a higher (not lower or unchanged) number of mutations than it did after diverging from its ancestor. Educational objective: Most genetic mutations are neutral and accumulate at a fairly constant rate across organisms over evolutionary time. The overall number of mutations in a species will therefore increase linearly across time. By analyzing the rate of neutral mutations in the genome, this "molecular clock" of evolution can be used to measure evolutionary time and estimate the evolutionary relationships between species.

Given That a Species Diverged from Its Ancestor 80 Million