Question 1

-The predatory bacterium Bdellovibrio bacteriovorus drills into a prey bacterium and,once inside,digests it.When the predatory bacterium attacks the gram-negative bacterium,what are the first structures penetrated by B.bacteriovorus on its way into the prey's cytoplasm?
A)lipopolysaccharides and an outer membrane
B)peptidoglycan layer and plasma membrane
C)lipopolysaccharides and plasma membrane
D)fimbriae and peptidoglycan layer

Accepted Answer

Bdellovibrio bacteriovorus targets gram-negative bacteria, which have an outer membrane covered by lipopolysaccharides. Thus, the first structures penetrated are the lipopolysaccharides and the outer membrane.

Question 2

The structure of a prokaryotic ribosome is not the same as a ribosome in an animal cell.As a result,which of the following is correct?
A)Some antibiotics can block protein synthesis in bacteria without harming the eukaryotic host.
B)Eukaryotes did not evolve from prokaryotes.
C)Translation can occur at the same time as transcription in eukaryotes but not in prokaryotes.
D)Some antibiotics can block the synthesis of peptidoglycan in the walls of bacteria.
E)Prokaryotes are unable to use a greater variety of molecules as food sources than can eukaryotes.

Accepted Answer

The difference in ribosome structure allows for some antibiotics to specifically target bacterial ribosomes and block protein synthesis without affecting eukaryotic ribosomes.

Question 3

Which of the following is a defining characteristic that all protocells or vesicles had in common?
A)the ability to synthesize enzymes
B)a surrounding membrane or membrane-like structure
C)RNA genes
D)the ability to replicate RNA

Accepted Answer

The defining characteristic that all protocells or vesicles had in common was a surrounding membrane or membrane-like structure. This membrane helped to contain and organize the contents of the protocell and separate it from its environment, allowing for the development of internal biochemical processes. The other choices (A, C, and D) are not necessarily defining characteristics of all protocells or vesicles. While some may have had the ability to synthesize enzymes, RNA genes, or replicate RNA, these traits were not universal to all early protocells or vesicles.

Question 4

The first genetic material on early Earth was most likely
A)DNA.
B)RNA.
C)peptidoglycan.
D)protocells.

Accepted Answer

RNA is believed to be the first genetic material on early Earth because it has the ability to both store genetic information and catalyze chemical reactions, which is essential for the development of life. DNA is a more stable form of genetic material, but it is believed to have evolved from RNA later on. Peptidoglycan and protocells are important components of bacterial cell walls and the study of the formation of life but not the first genetic material.

Question 5

What fossil evidence supports the hypothesis of modification by descent,or adaptation,of early Earth's bacteria?
A)the presence of distinct stromatolite morphologies and stromatolite formations in both lake and marine environments
B)cyanobacterium fossils,which have one of the earliest appearances in the fossil record
C)the presence on non-photosynthetic bacteria
D)the presence of spherical,rod-shaped,and spiral prokaryotes

Accepted Answer

Stromatolites, which are layered structures formed by the activity of microbial communities, show distinct morphologies and formations that indicate adaptation to different environments over time, supporting the hypothesis of modification by descent.

Question 6

The first genes on Earth were probably
A)DNA produced by reverse transcriptase from abiotically produced RNA.
B)DNA molecules whose information was transcribed to RNA and later translated in polypeptides.
C)self-replicating RNA molecules.
D)antibiotic resistant.

Accepted Answer

RNA is thought to be the first genetic material on Earth, and self-replicating RNA molecules would have been the first genes. This is known as the RNA world hypothesis. The other choices are not supported by current scientific understanding.

Question 7

Which of the following is an accurate characteristic of bacterial cell walls?
A)They are primarily made of chitin.
B)They prevent cells from shrinking in hypertonic environments.
C)They prevent cells from bursting in hypertonic environments.
D)They have peptidoglycan only if they are gram-negative.

Accepted Answer

Bacterial cell walls help prevent the cell from bursting in hypotonic environments by providing structural support and determining the shape of the cell. In hypertonic environments, water tends to move out of the cell, which could cause it to shrink, but the cell wall's primary function is to combat the lysis (bursting) in hypotonic environments where water would rush into the cell.

Question 8

Bacteria can rarely colonize and contaminate foods with high sugar content,such as syrup,honey,jelly,or bags of sugar,even if these products are left open in warm temperatures.The reason they do not become contaminated is because bacteria that encounter these foods
A)undergo death as a result of water loss from the cell.
B)are unable to metabolize the glucose,sucrose,or fructose and thus starve to death.
C)experience lysis.
D)are obligate anaerobes.
E)are unable to move through these thick and viscous materials.

Accepted Answer

Bacteria that encounter high sugar content foods undergo death due to osmotic pressure, which causes water to move out of the bacterial cell, leading to dehydration and death.

Question 9

Which of the following is likely the greatest impact that organisms have ever had on Earth?
A)Early cyanobacteria released hydrogen to Earth's atmosphere during the water-splitting step of photosynthesis.
B)Early cyanobacteria released carbon dioxide to Earth's atmosphere during the water-splitting step of photosynthesis.
C)Early cyanobacteria released oxygen to Earth's atmosphere during the water-splitting step of photosynthesis.
D)Early cyanobacteria released nitrogen to Earth's atmosphere during the water-splitting step of photosynthesis.

Accepted Answer

The release of oxygen into Earth's atmosphere by early cyanobacteria during photosynthesis had the greatest impact on Earth. This event, known as the Great Oxygenation Event, began about 2.4 billion years ago and was instrumental in the evolution of complex life on Earth. Oxygen allowed for the development of aerobic respiration, which is much more efficient at producing energy than anaerobic respiration. This allowed organisms to become larger and more complex, ultimately leading to the development of multicellular life. Additionally, oxygen in the atmosphere allowed for the formation of the ozone layer, which protects life on Earth from harmful UV radiation from the sun.

Question 10

On early Earth,more than 4 billion years ago,environmental conditions were very different from those today because
A)only early Earth was intensely bombarded by large rocks and ice from space.
B)only early Earth had an oxidizing atmosphere.
C)less ultraviolet radiation penetrated early Earth's atmosphere.
D)early Earth's atmosphere had significant quantities of ozone.

Accepted Answer

Early Earth was intensely bombarded by large rocks and ice from space, leading to volcanic activity and a lack of stability in the environment. This constant bombardment would have made environmental conditions very different from those today.

Question 11

On early Earth,what substance is hypothesized to have played a key role to facilitate the formation of polymers of amino acids,polymers of RNA,and vesicles?
A)DNA
B)sand,rock,or clay
C)peptidoglycan
D)biofilms

Accepted Answer

Sand, rock, or clay are hypothesized to have played a key role in facilitating the formation of polymers of amino acids, polymers of RNA, and vesicles on early Earth. These substances could have acted as catalysts, providing a surface for the molecules to bind to and facilitating the formation of complex structures.

Question 12

Which portion of a typical prokaryotic flagellum is embedded in the cell wall and plasma membrane? 
A)a hook
B)a complex "motor"
C)a filament
D)a pili

Accepted Answer

The answer of Which portion of a typical prokaryotic flagellum...

Question 13

Bacteria are able to adhere to substrates and to other individuals by using which structures?
A)capsules and endospores
B)capsules and fimbriae
C)endospores and fimbriae
D)fimbriae and plasmids
E)fimbriae and flagella

Accepted Answer

Bacteria are able to adhere to substrates and to other individuals by using structures called fimbriae, which are thin, hair-like appendages that protrude from the surface of the cell. Capsules are not involved in adhesion, but rather serve to protect the bacteria from their environment. Endospores are dormant, resistant structures that form inside some bacteria, and are not involved in adhesion. Plasmids are small, circular pieces of DNA that can be exchanged between bacteria, but do not play a role in adhesion. Flagella are whip-like appendages that bacteria use for movement, but are not involved in adhesion.

Question 14

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 challenging and would have the greatest impact on our understanding if we were able to answer it?
A)How can amino acids,simple sugars,and nucleotides be synthesized abiotically?
B)How can RNA molecules catalyze reactions?
C)How did RNA sequences come to carry the code for amino acid sequences?
D)How could polymers involving lipids and/or proteins form membranes in aqueous environments?
E)How can RNA molecules act as templates for the synthesis of complementary RNA molecules?

Accepted Answer

Understanding how RNA sequences came to carry the code for amino acid sequences would give us a better insight into the early stages of the evolution of life on Earth. It would help us understand how the first living systems arose from the mixture of chemicals on the primordial Earth. This would have a greater impact on our understanding of the origin of life than the other choices listed.

Question 15

Approximately how far back in time does the fossil record extend?
A)3.5 million years
B)5.0 million years
C)3.5 billion years
D)5.0 billion years

Accepted Answer

The fossil record extends back approximately 3.5 billion years, to the origins of life on Earth.

Question 16

According to scientists' hypotheses,prokaryotes most likely evolved prior to eukaryotes because
A)prokaryotic cells lack nuclei.
B)the meteorites that have struck Earth contain fossils only of prokaryotes.
C)laboratory experiments have produced ribosomes abiotically.
D)ribosomes closely resemble prokaryotic cells.
E)the oldest fossilized cells resemble prokaryotes.

Accepted Answer

The oldest fossilized cells found resemble prokaryotes, suggesting that they evolved before eukaryotes. Other options, such as the lack of nuclei in prokaryotic cells or the similarity of ribosomes to prokaryotic cells, are characteristics of prokaryotes but do not provide a direct explanation for their evolutionary timeline. The presence of prokaryotic fossils in meteorites or laboratory experiments producing ribosomes abiotically are not currently supported by scientific evidence.

Question 17

Which of the following is the correct sequence of events in the origin of life?
A)formation of protocells,synthesis of organic molecules,synthesis of organic macromolecules,formation of DNA-based genetic systems
B)formation of protocells,synthesis of organic macromolecules,synthesis of organic molecules,formation of DNA-based genetic systems
C)synthesis of organic molecules,synthesis of organic macromolecules,formation of protocells,formation of DNA-based genetic systems
D)synthesis of organic molecules,synthesis of organic macromolecule,formation of DNA-based genetic systems,formation of protocells

Accepted Answer

The correct sequence starts with the synthesis of organic molecules, followed by the synthesis of organic macromolecules. These steps are necessary before the formation of protocells, which eventually leads to the formation of DNA-based genetic systems. This sequence reflects the gradual complexity increase in the origin of life.

Question 18

In 2009,which of the following did scientists discover was possible on early Earth?
A)abiotic synthesis of RNA monomers
B)bacterial cell walls made mainly of chitin
C)gram-positive bacteria with outer membranes that contain lipopolysaccharides
D)gram-negative bacteria with cell walls composed of a thick layer of peptidoglycan

Accepted Answer

In 2009, scientists discovered that abiotic synthesis of RNA monomers was possible on early Earth. This was a key step in the development of life as RNA is believed to have been one of the first molecules capable of both storing genetic information and catalyzing chemical reactions.

Question 19

What structure(s)can allow a bacterium to persist,often over extended periods of time,in extreme environments such as those lacking in nutrients,dehydrating,and freezing,or in very hot temperatures?
A)nucleoids
B)capsules or endospores
C)plasmids
D)peptidoglycan
E)fimbriae

Accepted Answer

Capsules or endospores are structures that allow bacteria to persist in extreme environments. Capsules protect the bacteria from desiccation and nutrient depletion, while endospores are dormant structures that can survive very hot or very cold temperatures and lack of nutrients for extended periods of time. Nucleoids, plasmids, peptidoglycan, and fimbriae do not specifically provide persistence in extreme environments.

Question 20

Suppose it were possible to conduct sophisticated microscopic and chemical analyses of microfossils found in 3.5-billion-year-old rock formations.Which of the following structures would be surprising to observe?
A)RNA
B)vesicles with a membrane
C)a nucleus
D)ribozymes

Accepted Answer

The presence of a nucleus in 3.5-billion-year-old rock formations would be surprising because nuclei did not evolve until much later in the history of life on Earth. The other options (RNA, vesicles with a membrane, ribozymes) are all plausible components of early life forms.

Quiz 24: Early Life and the Diversification of Prokaryotes

-The predatory bacterium Bdellovibrio bacteriovorus drills into a prey bacterium and,once inside,digests it.When the predatory bacterium attacks the gram-negative bacterium,what are the first structures penetrated by B.bacteriovorus on its way into the prey's cytoplasm?

The structure of a prokaryotic ribosome is not the same as a ribosome in an animal cell.As a result,which of the following is correct?

Which of the following is a defining characteristic that all protocells or vesicles had in common?

The first genetic material on early Earth was most likely

What fossil evidence supports the hypothesis of modification by descent,or adaptation,of early Earth's bacteria?

The first genes on Earth were probably

Which of the following is an accurate characteristic of bacterial cell walls?

Bacteria can rarely colonize and contaminate foods with high sugar content,such as syrup,honey,jelly,or bags of sugar,even if these products are left open in warm temperatures.The reason they do not become contaminated is because bacteria that encounter these foods

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

On early Earth,more than 4 billion years ago,environmental conditions were very different from those today because

On early Earth,what substance is hypothesized to have played a key role to facilitate the formation of polymers of amino acids,polymers of RNA,and vesicles?

Which portion of a typical prokaryotic flagellum is embedded in the cell wall and plasma membrane?

Bacteria are able to adhere to substrates and to other individuals by using which structures?

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 challenging and would have the greatest impact on our understanding if we were able to answer it?

Approximately how far back in time does the fossil record extend?

According to scientists' hypotheses,prokaryotes most likely evolved prior to eukaryotes because

Which of the following is the correct sequence of events in the origin of life?

In 2009,which of the following did scientists discover was possible on early Earth?

What structure(s) can allow a bacterium to persist,often over extended periods of time,in extreme environments such as those lacking in nutrients,dehydrating,and freezing,or in very hot temperatures?

Suppose it were possible to conduct sophisticated microscopic and chemical analyses of microfossils found in 3.5-billion-year-old rock formations.Which of the following structures would be surprising to observe?