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Chapter 33 : Analyzing Evolutionary Changes
In this activity, students count the differences in amylase amino acid sequences from seven different organisms and use the data to construct a simple evolutionary tree. Evolution is a unifying theme in biology. Students often learn about the evolution of plants and animals from single-celled progenitors, with discussions of adaptations and niches. This chapter looks at evolution of the protein amylase at the molecular level. Proteins from closely related organisms are more similar to one another than are proteins from less closely related organisms. A mutation in one of the proteins could result in large morphological changes. A specific type of change associated with speciation is a change in the timing of body maturity and reproduction. The accumulation of genome sequences is making it easier for researchers to trace evolutionary changes. Evolution requires genetic change, such as mutations or chromosomal rearrangements, and the fixation of the new genotype in a population. If a slightly deleterious change in a protein that for a different reason had a survival advantage arose in an organism, that deleterious change could become fixed. Conserved protein sequences also support the hypothesis that the various proteins are descendants of an ancestral form. If necessary, the student can review the relationship between DNA sequence and protein sequence, emphasizing how changes in DNA can cause changes in proteins. The point of this activity is not the method for producing an evolutionary tree. Rather, it is the idea of protein evolution.