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Exam 24: Early Life and the Diversification of Prokaryotes

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Question 1

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What is a main difference between endotoxins and exotoxins?

A) Endotoxins are proteins and exotoxins are lipopolysaccharides.
B) Endotoxins are lipopolysaccharides and exotoxins are proteins.
C) Exotoxins are released only when the bacteria die and their cell walls break down.
D) Exotoxins are made of RNA and endotoxins are made of DNA.

E) A) and B)
F) A) and C)

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Question 2

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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

A) 1, 3, 4
B) 2, 3, 4
C) 2, 4, 1
D) 1, 2, 5
E) 1, 2, 3

F) C) and E)
G) B) and D)

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Question 3

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Prokaryotes' essential genetic information is located in the

Which of the following statements is not true?

The table depicts characteristics of five prokaryotic species (A-E) . Use the information in the table to answer the following question(s) . Table 24.1 -Which two species might be expected to cooperate metabolically, perhaps forming a biofilm wherein one species surrounds cells of the other species?

Plantlike photosynthesis that releases O₂ occurs in

Please use the following information to answer the question(s) below. 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 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's ability to survive in a human who is taking penicillin pills may be due to the presence of which of the following? 1) penicillin-resistance genes 2) a gram-positive cell wall 3) a gram-negative cell wall 4) an endospore

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 question(s) . Figure 24.2 -Data were collected from the heterocysts of a nitrogen-fixing cyanobacterium inhabiting equatorial ponds. Study the following figure 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 question(s) . Figure 24.2 -Which question arising from the results depicted in Figure 24.2 is most interesting from a genetic perspective and has the greatest potential to increase our knowledge base?

Which of the following is likely the greatest impact that organisms have ever had on Earth?

Bacteria participate in many ecological interactions. Which role typically does not involve symbiosis?

The predatory bacterium Bdellovibrio bacteriovorus drills into a prey bacterium and, once inside, digests it. In an attack upon a gram-negative bacterium that has a slimy cell covering, what is the correct sequence of structures penetrated by B. bacteriovorus on its way to the prey's cytoplasm? 1) membrane composed mostly of lipopolysaccharide 2) membrane composed mostly of phospholipids 3) peptidoglycan 4) capsule

Several scientific laboratories across the globe are involved in research concerning the origin of life on Earth. Which of these questions is currently the most problematic and would have the greatest impact on our understanding if we were able to answer it?

The table depicts characteristics of five prokaryotic species (A-E) . Use the information in the table to answer the following question(s) . Table 24.1 -Which species is most likely to be found both in sewage treatment plants and in the guts of cattle?

Please use the following information to answer the question(s) below. Nitrogenase, the enzyme that catalyzes nitrogen fixation, is inhibited whenever free O₂ reaches a critical concentration. Consequently, nitrogen fixation cannot occur in cells wherein photosynthesis produces free O₂. Consider the colonial aquatic cyanobacterium Anabaena, whose heterocytes are described as having "a thickened cell wall that restricts entry of O₂ produced by neighboring cells. Intracellular connections allow heterocysts to transport fixed nitrogen to neighboring cells in exchange for carbohydrates." -Given that the enzymes that catalyze nitrogen fixation are inhibited by oxygen, what are two "strategies" that nitrogen-fixing prokaryotes might use to protect these enzymes from oxygen? 1) package them in membranes that are impermeable to all gases 2) be obligate anaerobes 3) be facultative aerobes 4) package these enzymes in specialized cells or compartments that inhibit oxygen entry

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 question(s) . Figure 24.2 -During which two times can the recipient accurately be described as "recombinant" due to the sequence of events portrayed in Figure 24.2?

Jams, jellies, preserves, honey, and other foodstuffs with high sugar content hardly ever become contaminated by bacteria, even when the food containers are left open at room temperature. This is because bacteria that encounter such an environment

In general, what is the primary ecological role of prokaryotes?

Scientists have identified two major branches of prokaryotic evolution. What was the basis for dividing prokaryotes into two domains?

The following question(s) 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. -Certain proteins of the complex motor that drives bacterial flagella are modified versions of proteins that had previously belonged to plasma membrane pumps. This evidence supports the claim that