Changes in the nucleotide sequence of DNA and amino acid sequence in proteins can be thought of as molecular fossils. That is, these changes act as historical records of evolutionary events and give us clues about the relatedness of different species in much the same way that changes in morphological characters, preserved in the form of fossils, give us clues about change over time. The extraordinary growth of sequence databases, along with the development of tools to explore and mine these databases, has radically enhanced the ability of biologists to uncover the patterns of organic evolution that have occurred throughout the history of life on Earth.
The following MicrobesCount! investigation can act as a springboard for you to pose evolutionary questions:
- Where would you expect Methanococcus and Pyrococcus to split off of the unrooted tree if the two domain (i.e., Bacteria and Eukarya) hypothesis is correct?
- Where would you expect Methanococcus and Pyrococcus to split off of the unrooted tree if the three domain (i.e., Bacteria, Archaea and Eukarya) hypothesis is correct?
- Did the species you added appear on the tree where you predicted?
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