Exam 24: Early Life and the Diversification of Prokaryotes

How were conditions on the early Earth of more than 3 billion years ago different from those on today's Earth?

Chloramphenicol is an antibiotic that targets prokaryotic (70S) ribosomes, but not eukaryotic (80S) ribosomes. Which of these questions stems from this observation, plus an understanding of eukaryotic origins?

Use the information in the following paragraph to answer the next few questions. A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the intestinal lining. It adheres to the intestinal lining using a feature that also protects it from phagocytes, bacteriophages, and dehydration. Fecal matter from a human in whose intestine this bacterium lives can spread the bacterium, even after being mixed with water and boiled. The bacterium is not susceptible to the penicillin family of antibiotics. It contains no plasmids and relatively little peptidoglycan. -This bacterium derives nutrition by digesting human intestinal contents (in other words, food). Humans lacking this bacterium have no measurable reproductive advantage or disadvantage relative to humans who harbor this bacterium. Consequently, the bacterium can be properly described as which of the following? 1. symbiont 2) endosymbiont 3) mutualist 4) commensal

Regarding prokaryotic genetics, which statement is correct?

If a bacterium regenerates from an endospore that did not possess any of the plasmids that were contained in its original parent cell, the regenerated bacterium will probably also

The data were collected from the heterocysts of a nitrogen-fixing cyanobacterium inhabiting equatorial ponds. Study the graph in Figure 24.3 and choose the most likely explanation for the shape of the curve. Figure 24.3

Figure 24.2 depicts changes to the amount of DNA present in a recipient cell that is engaged in conjugation with an Hfr cell. Hfr cell DNA begins entering the recipient cell at Time A. Assume that reciprocal crossing over occurs (in other words, a fragment of the recipient's chromosome is exchanged for a homologous fragment from the Hfr cell's DNA). Use Figure 24.2 to answer the following questions. Figure 24.2 -How is the recipient cell different at Time D than it was at Time A?

If it were possible to conduct sophisticated microscopic and chemical analyses of microfossils found in 3.2-billion-year-old stromatolites, then one should be surprised to observe evidence of which of the following within such microfossils? I. double-stranded DNA II. a nuclear envelope III. a nucleoid IV. a nucleolus V. ribosomes

Which species might be able to include Hfr cells?

The typical prokaryotic flagellum features

Match the numbered terms to the description that follows. Choose all appropriate terms. 1. autotroph 2) heterotroph 3) phototroph 4) chemotroph An organism that obtains both carbon and energy by ingesting prey

Foods can be preserved in many ways by slowing or preventing bacterial growth. Which of these methods should be least effective at inhibiting bacterial growth?

Which statement about bacterial cell walls is false?

Carl Woese and collaborators identified two major branches of prokaryotic evolution. What was the basis for dividing prokaryotes into two domains?

If the experimental population of E. coli lacks an F factor or F plasmid, and if bacteriophages are excluded from the bacterial cultures, then which of these is (are) means by which beneficial mutations might be transmitted horizontally to other E. coli cells?

The following questions refer to Figure 24.1. In this eight-year experiment, 12 populations of E. coli, each begun from a single cell, were grown in low-glucose conditions for 20,000 generations. Each culture was introduced to fresh growth medium every 24 hours. Occasionally, samples were removed from the populations, and their fitness in low-glucose conditions was tested against that of members sampled from the ancestral (common ancestor) E. coli population. Figure 24.1 -Which of the following, if it occurs in the absence of any other type of adaptation listed here, is least reasonable in terms of promoting bacterial survival over evolutionary time in a low-glucose environment?

If the vertical axis of Figure 24.1 refers to "Darwinian fitness," then which of the following is the most valid and accurate measure of fitness?

The following questions are based on the observation that several dozen different proteins comprise the prokaryotic flagellum and its attachment to the prokaryotic cell, producing a highly complex structure. -If the complex protein assemblage of the prokaryotic flagellum arose by the same general processes as those of the complex eyes of molluscs (such as squids and octopi), then

In Fred Griffith's experiments, harmless R strain pneumococcus became lethal S strain pneumococcus as the result of which of the following? 1. horizontal gene transfer 2) transduction 3) conjugation 4) transformation 5) genetic recombination

In a hypothetical situation, a bacterium lives on the surface of a leaf, where it obtains nutrition from the leaf's nonliving, waxy covering while inhibiting the growth of other microbes that are plant pathogens. If this bacterium gains access to the inside of a leaf, however, it causes a fatal disease in the plant. Once the plant dies, the bacterium and its offspring decompose the plant. What is the correct sequence of ecological roles played by the bacterium in the situation described here? Use only those that apply. 1. nutrient recycler 2) mutualist 3) commensal 4) pathogen 5) primary producer