Micro Chapter 17

Which of the following is true of rRNA sequences? Select one: a. Certain regions of rRNAs are highly conserved among organisms. b. They cannot be used to construct phylogenetic trees. c. They resist being amplified by PCR. d. The genes encoding them are only present in some organisms.

a. Certain regions of rRNAs are highly conserved among organisms.

Defining bacterial species currently relies on __________ as these provide the best measures of similarity and divergence. Select one: a. DNA relatedness and sharing of ecological niche b. morphological traits and lifestyle c. DNA relatedness and RNA relatedness d. DNA relatedness and capacity of horizontal gene transfer

a. DNA relatedness and sharing of ecological niche

A clade is Select one: a. a group of organisms that share a common ancestor not shared by other organisms. b. a group of organisms that are similar in size and shape (morphology). c. a family of extinct organisms. d. another name for a paraphyletic group.

a. a group of organisms that share a common ancestor not shared by other organisms.

Cyanobacteria changed the atmosphere on early Earth because they led to increased Select one: a. atmospheric O2 levels. b. nitrogen levels. c. water levels in the oceans. d. reduced, soluble forms of iron.

a. atmospheric O2 levels.

Organisms acquire DNA Select one: a. via horizontal transmission from cells of any domain, and also from vertical transmission. b. via horizontal transmission, but only from cells of the same domain, and also from vertical transmission. c. via horizontal transmission, but only from cells of the same species, and also from vertical transmission. d. only from their parent cell via vertical transmission.

a. via horizontal transmission from cells of any domain, and also from vertical transmission.

Which of the following have NOT been used as evidence for life during the Archaean eon? Select one: a. Chemical biosignatures b. Fossil eukaryotes c. Isotope ratios d. Fossil stromatolites

b. Fossil eukaryotes

The core genome is Select one: a. the whole chromosomal genome but without plasmids. b. all genes found in all sequenced genomes of a species. c. all expected genes in all possible isolates. d. the whole chromosomal genome and all plasmid genes.

b. all genes found in all sequenced genomes of a species.

The taxonomic rank "order" belongs between Select one: a. genus and species. b. class and family. c. domain and phylum. d. family and genus.

b. class and family.

Emerging clades include all of the following EXCEPT Select one: a. candidate species. b. laboratory strains. c. uncultured organisms. d. environmental samples.

b. laboratory strains.

The metabolist model attempts to explain Select one: a. how the first cells became encapsulated by lipid membranes. b. the origin of biosynthesis on the basis of CO2 fixation. c. how DNA became the hereditary material. d. how the first nucleic acids formed.

b. the origin of biosynthesis on the basis of CO2 fixation

What do eukaryotes and archaea have in common that is lacking from bacteria? Select one: a. Unique membrane lipids in the cell membrane b. The presence of ribosomes c. Splicing machinery for introns d. A membrane surrounding the genetic material

c. Splicing machinery for introns

Which of the following is correct regarding stromatolites? Select one: a. Fossil stromatolites are made of layers of igneous rock. b. Living stromatolites can be found in the human colon. c. Stromatolites are the oldest forms of life for which there is clear fossil evidence. d. Living stromatolites grow on the deepest parts of the ocean floor as mats of cyanobacteria.

c. Stromatolites are the oldest forms of life for which there is clear fossil evidence.

Mitochondria and chloroplasts are surrounded by Select one: a. a double membrane, the inner one from the host and the outer one from the bacterial endosymbiont. b. three membranes. c. a double membrane, the inner one from the bacterial endosymbiont and the outer one derived from the host. d. a single membrane.

c. a double membrane, the inner one from the bacterial endosymbiont and the outer one derived from the host

Symbioses are Select one: a. relationships where one species lives inside the other's body. b. all negative relationships. c. any relationship with two unrelated species. d. all positive relationships.

c. any relationship with two unrelated species.

One reason why RNA molecules are the leading candidate as the first informational molecule is that Select one: a. RNA molecules are usually double stranded. b. RNA serves as the hereditary material in today's prokaryotic cells. c. some RNA molecules can function as enzymes. d. RNA nucleotides are a major component of cell membranes.

c. some RNA molecules can function as enzymes.

What assumption is made when a molecular clock is used to date species divergence? Select one: a. All cells have a one-day doubling time. b. All species contain the same genes. c. In cells, the rate of protein turnover is 24 hours. d. The mutation rate remains constant.

d. The mutation rate remains constant.

Although the exact definition of a species for prokaryotes is debated, two individual bacteria can often be considered members of a single species if they Select one: a. can mate and produce fertile offspring. b. have a high degree of morphological similarity. c. can be cocultured because they have the same growth requirements. d. have a high degree of DNA similarity.

d. have a high degree of DNA similarity.

Organisms in the genus Wolbachia bacteria are Select one: a. vertebrate endosymbionts. b. free-living bacteria. c. plant endosymbionts. d. invertebrate endosymbionts.

d. invertebrate endosymbionts

Reductive evolution is the Select one: a. decrease in species number over time due to extinction. b. opposite of oxidative evolution. c. evolutionary decrease in body size of organisms over time. d. loss or mutation of DNA encoding unselected traits.

d. loss or mutation of DNA encoding unselected traits.

A major mechanism of microbial evolution is genome duplication and divergence as discussed in Chapter 9. This allows for existing genes to acquire mutations as there is a "backup" copy of the gene that will continue to function. Genes that have diverged through mutation to have different function are called Select one: a. orthologs. b. homologs. c. analogs. d. paralogs.

d. paralogs.