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GBio 153 Chapter 24

Terms in this set (30)

Scientists hypothesize that prokaryotes evolved before eukaryotes because
the oldest fossilized cells resemble prokaryotes.
Approximately how far back in time does the fossil record extend?
3.5 billion years
Which of the following steps has not yet been accomplished by scientists studying the origin of life?
formation of protocells that use DNA to direct the polymerization of amino acids
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
undergo death as a result of water loss from the cell.
Mitochondria are thought to be the descendants of certain alpha proteobacteria. They are, however, no longer able to lead independent lives because most genes originally present on their chromosome have moved to the nuclear genome. Which phenomenon accounts for the movement of these genes?
horizontal gene transfer
Suppose it were possible to conduct sophisticated microscopic and chemical analyses of microfossils found in 3.5-billion-year-old stromatolites. Which of the following structures would be surprising to observe?
I. RNA
II. vesicles
III. a nucleus
IV. ribozymes
III
Which of the following is the correct sequence of events in the origin of life?
I. formation of protobionts
II. synthesis of organic monomers
III. synthesis of organic polymers
IV. formation of DNA-based genetic systems
II, III, I, IV
A fish that has been salt-cured subsequently develops a reddish color. You suspect that the fish has been contaminated by the extreme halophile Halobacterium. Which of these features of cells removed from the surface of the fish, if confirmed, would support your suspicion?
1. the presence of the same photosynthetic pigments found in cyanobacteria
2. cell walls that lack peptidoglycan
3. cells that are isotonic to conditions on the surface of the fish
4. cells unable to survive salt concentrations lower than 9%
5. the presence of very large numbers of ion pumps in the plasma membrane
2, 3, 4, and 5
How were conditions on the early Earth of more than 3 billion years ago different from those on today's Earth?
Only early Earth was intensely bombarded by large space debris.
Which of the following is likely the greatest impact that organisms have ever had on Earth?
Early cyanobacteria released oxygen to Earth's atmosphere during the water-splitting step of photosynthesis.
Which two structures play direct roles in permitting bacteria to adhere to each other or to other surfaces?
1. capsules
2. endospores
3. fimbriae
4. plasmids
5. flagella
1 and 3
Plantlike photosynthesis that releases O2 occurs in
cyanobacteria.
Photoautotrophs use
light as an energy source and CO2 as a carbon source.
The first genes on Earth were probably
self-replicating RNA molecules.
Which of the following is a defining characteristic that all protobionts had in common?
a surrounding membrane or membrane-like structure
Prokaryotes' essential genetic information is located in the
nucleoid.
Fossilized stromatolites
resemble structures formed by bacterial communities that are found today in some shallow marine bays.
Match the numbered terms to the description that follows. Choose all appropriate terms.
1. autotroph
2. heterotroph
3. phototroph
4. chemotroph
a prokaryote that obtains both energy and carbon as it decomposes dead organisms
2 and 4
Which of the following oxidizes inorganic substances to obtain energy that is used, in part, to fix CO2?
chemoautotrophs
In Figure 24.1, data are presented from an eight-year experiment in which 12 populations of Escherichia 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 24.1If 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?
number of offspring or close kin that survive to reproductive age
Which of these statements about prokaryotes is correct?
They divide by binary fission, without mitosis or meiosis.
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
2 and 4
Which of the following is an accurate characteristic of bacterial cell walls?
They prevent cells from bursting in hypotonic conditions.
Bacteria participate in many ecological interactions. Which role typically does not involve symbiosis?
decomposing dead organisms and organic wastes
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
4, 1, 3, 2
In Figure 24.1, data are presented from an eight-year experiment in which 12 populations of Escherichia 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 24.1E. coli cells typically make most of their ATP by metabolizing glucose. Under the conditions of this experiment, what should be true of E. coli's generation time (especially early in the course of the experiment, but less so later on)?
Generation time should be slower than in the typical environment.
Genetic variation in bacterial populations cannot result from
meiosis.
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
2, 4, 1
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 energy from light
3 only
The first genetic material on early Earth was most likely
RNA.
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