On the origin of Eukaryotes.pdf

On the origin of Eukaryotes.pdf - On the origin of...

This preview shows page 1 - 2 out of 4 pages.

On the origin of Eukaryotes 1. Why did Carl Woese and his colleagues look at 16S rRNA in a wide range of prokaryotes and eukaryotes? What did their data tell them about the various groups of living organisms? Scientists first divided life into prokaryotes and eukaryotes in the mid-1900s, using increasingly powerful microscopes to see the fine details of cells. But they couldn't say much about how prokaryotes and eukaryotes were related. Did the two groups branch off from a common ancestor? Or did eukaryotes evolve from a particular lineage of prokaryotes long after the evolution of the first prokaryotes? They reasoned that species with similar sequences were closely related and used that reasoning to draw a tree of life. Eukaryotes were all more closely related to one another than any were to prokaryotes, they found, which suggests that eukaryotes all belong to a single lineage and that the eukaryote cell evolved only once in the history of life. But Woese and his colleagues got a surprise when they looked at the prokaryotes. The prokaryotes formed two major branches in their analysis. One branch included familiar bacteria such as E. coli. The other branch included a motley crew of obscure microbes methane-producing organisms that can survive on hydrogen in oxygen-free swamps, for example, and others that live in boiling water around deep-sea hydrothermal vents. Woese and his colleagues argued that there were three major groups of living things: eukaryotes, bacteria, and a group they dubbed archaea. And most surprising of all,
Image of page 1

Subscribe to view the full document.

Image of page 2

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern