A gram-negative cell wall consists of __________.

A new organism has been discovered. Tests have revealed that it is unicellular, is autotrophic, and has a cell wall that contains peptidoglycan. Based on this evidence, it should be classified as a(n)a. alga.b. archaean.c. protist.d. bacterium.

The bacteria that cause tetanus can be killed only by prolonged heating at temperatures considerably above boiling. This suggests that tetanus bacteriaa. have cell walls containing peptidoglycan.b. secrete endotoxins.c. are autotrophic.d. produce endospores.

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. The Bacteria and Archaea both include microscopic prokaryotes that lack membrane-bound nuclei. What criteria have led to the classification of these two groups as separate domains?

Gram-negative bacteria have __________ peptidoglycan than gram-positive cells, and their cell walls are __________ complex structurally.

Bacteria that __________ tend to have abundant internal membranes.

Bacterial flagella have a very complex structure composed of 42 distinct proteins. What is the most likely explanation for the evolution of these complex structures?

The bacteria that cause tetanus can be killed only by prolonged heating at temperatures considerably above boiling. This suggests that these bacteria __________.

Using the figure below, describe the stages that may have led to the origin of life.