Which group of bacteria is unusual in that they lack peptidoglycan in their cell walls?

The traditional tree of life (shown above) presents the three domains as distinct, monophyletic lineages. However, other hypotheses propose different views on the relationships among the Archaea, Bacteria, and Eukarya. In particular, the two-domain hypothesis—or eocyte hypothesis—is emerging as a well-supported alternative to the three-domain hypothesis. The eocyte hypothesis, illustrated below, suggests that eukaryotes evolved from eocytes (also known as the Crenarchaeota—a major lineage of the Archaea). Resolving the relationships among these ancient lineages is difficult, but it has profound implications on our understanding of the origin of eukaryotic cells. What other types of evidence or features might be used to ascertain whether the tree of life is best represented according to the three-domain or the eocyte hypothesis?

Which of the following groups of prokaryotes is classified as a member of the domain Archaea?

Which subgroup of proteobacteria contains many species that are closely associated with eukaryotic hosts in mutualistic or parasitic relationships?

Portions of the genomes of certain prokaryotic species are very similar to portions of the genomes of distantly related prokaryotes. The process that most likely accounts for this genetic similarity is __________.

Prokaryotes found inhabiting the Great Salt Lake would be __________.

Which clade of archaea includes most of the extreme thermophiles?

Scientists hypothesize that the O157:H7 strain of E. coli is so different from the K-12 strain because of __________.

Which of the following is a difference between bacteria and archaea?