Exam 26: Bacteria and Archaea

Which of the following is not one of the metabolic capabilities found in Archaea that enable them to live in hydrothermal vents, acidic or salty water, and the rumens of cows?

Based on the characteristics of crenarchaeote archaeons and euryarchaeote archaeons, these organisms likely first evolved in oxygen-poor habitats.

Consider the chemical reactions of the sulfur cycle shown in Figure 26.10. Oceans constitute the most significant reservoir of sulfur in the biosphere, and sulfate (SO₄^2-) reduction is the predominant form of anaerobic respiration in marine environments. In such cases, oxidized sulfur compounds like SO₄^2- are the electron acceptors instead of what?

The fossil record shows life originated on Earth at least 3.5 billion years ago and consisted entirely of microorganisms. Paleontologists provide the strongest evidence of this conclusion through the discovery of:

How do cattle digest complex plant polysaccharides like cellulose?

Bioluminescence, as seen in squids, is possible because:

Why is genomic information often more useful than phenotypic information in the bacterial phylogenetic tree?

Some shared metabolic capabilities such as anoxygenic photosynthesis or nitrogen fixation are a result of convergent evolution.

Plasmid DNA generally contains genetic information critical for the survival of a bacterial cell.

In which of the following environments would you NOT expect to find various crenarchaeote archaeons?

It has been suggested that cyanobacteria are the most important organisms to have evolved on the Earth. What evidence justifies this view?

Which of these trees reflects the hypothesis that Archaea are more closely related to Eukarya than they are to Bacteria?

Based on the energy and carbon sources used by humans, in what way would humans be classified?

Photoheterotrophs rely on sunlight and organic molecules obtained from the environment.

A researcher is comparing the sequences of genes encoding cell wall proteins in archaeons with those coding cell wall proteins in bacteria. How similar do you expect these sequences will be?

Scientists generate phylogenetic trees for a group of organisms using molecular data such as gene sequences. The 16S rRNA gene is used for this type of analysis because the gene phylogeny accurately reproduces the evolutionary history of the organisms from which the sequences were derived. Assume that the phylogeny below, which was produced based on analysis of the 16S rRNA gene, represents the evolutionary history of bacteria. You are interested in determining other genes that may be used to recover the same phylogeny. For each microbe in the tree, you sequence two other genes. The first is rpoB, which encodes one of the subunits in RNA polymerase holoenzyme and is located on the bacterial chromosome. The second is cat, a gene that confers resistance to the antibiotic chloramphenicol (a drug that targets the ribosome) and is located on a plasmid. Examine the two trees below. On the left is the phylogeny recovered using cat sequences and on the right is the phylogeny recovered using rpoB sequences. One of the two trees supports the hypothesis presented in the 16S rRNA gene phylogeny for this group of bacteria. Which of the following helps to explain why only one of the two trees matches the 16S rRNA gene phylogeny?

Organisms belonging to the Bacteria branch of the tree of life can demonstrate which of the following processes?

Even without the nitrogen cycle, life on Earth would continue with minimal interruption due to compensation by the carbon and sulfur cycles.

Stromatolites are of particular interest to researchers as they can provide a record of microbial sediment deposits over the last 3.5 billion years of Earth's history.

An organism classified as a eukaryote could be which of the following?