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Questions and Answers
What is the primary energy source at Deep-Sea Hydrothermal Vents according to the text?
What is the primary energy source at Deep-Sea Hydrothermal Vents according to the text?
In the context of the text, what is the role of impact from meteorites in 'Synthesis by Destruction'?
In the context of the text, what is the role of impact from meteorites in 'Synthesis by Destruction'?
What is the function of clay in 'Macromolecule Assembly' as described in the text?
What is the function of clay in 'Macromolecule Assembly' as described in the text?
What is the key aspect of RNA's role in 'Reproduction of Macromolecules' according to the RNA World hypothesis?
What is the key aspect of RNA's role in 'Reproduction of Macromolecules' according to the RNA World hypothesis?
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What does research suggest about molecules synthesized under prebiotic conditions in relation to the 'System Assembly' described in the text?
What does research suggest about molecules synthesized under prebiotic conditions in relation to the 'System Assembly' described in the text?
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Which hypothesis suggests that organic molecules were synthesized when comets or asteroids struck the early Earth?
Which hypothesis suggests that organic molecules were synthesized when comets or asteroids struck the early Earth?
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What was the main energy source used in the Miller-Urey Experiment to simulate lightning?
What was the main energy source used in the Miller-Urey Experiment to simulate lightning?
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Where was extraterrestrial organic matter, dated to be 3.3 billion years old, found?
Where was extraterrestrial organic matter, dated to be 3.3 billion years old, found?
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Which hypothesis suggests that organic molecules were synthesized at hydrothermal vents on the ocean floor?
Which hypothesis suggests that organic molecules were synthesized at hydrothermal vents on the ocean floor?
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What were the main building blocks formed in the Primordial Soup according to the Oparin-Haldane Hypothesis?
What were the main building blocks formed in the Primordial Soup according to the Oparin-Haldane Hypothesis?
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Which step of a virus lifecycle involves the synthesis of viral proteins and genome by the host cell?
Which step of a virus lifecycle involves the synthesis of viral proteins and genome by the host cell?
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In the context of viral classification, which criteria are used to classify viruses?
In the context of viral classification, which criteria are used to classify viruses?
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Which of the following is true about the attachment phase in a virus lifecycle?
Which of the following is true about the attachment phase in a virus lifecycle?
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Which mechanism is typically involved in the entry phase of a virus lifecycle for bacteriophages?
Which mechanism is typically involved in the entry phase of a virus lifecycle for bacteriophages?
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What is the main function of the tails in bacteriophages like the one shown in the transmission electron micrograph?
What is the main function of the tails in bacteriophages like the one shown in the transmission electron micrograph?
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Which process is NOT involved in the mystery of the origins of life on Earth?
Which process is NOT involved in the mystery of the origins of life on Earth?
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What were the conditions on early Earth that scientists believe supported the development of life?
What were the conditions on early Earth that scientists believe supported the development of life?
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Which process is required for the assembly of macromolecules but is NOT associated with the mystery of the origins of life?
Which process is required for the assembly of macromolecules but is NOT associated with the mystery of the origins of life?
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What specific event allowed for the condensation to form oceans during Earth's early history?
What specific event allowed for the condensation to form oceans during Earth's early history?
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Which of the following is a common problem that needs to be solved to account for the origin of life on Earth?
Which of the following is a common problem that needs to be solved to account for the origin of life on Earth?
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What is the main difference between the regressive hypothesis and the progressive hypothesis mentioned in the text?
What is the main difference between the regressive hypothesis and the progressive hypothesis mentioned in the text?
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Which statement is true regarding virus morphology based on the text?
Which statement is true regarding virus morphology based on the text?
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What is a characteristic of naked viruses according to the text?
What is a characteristic of naked viruses according to the text?
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Which statement accurately describes the virus genome as mentioned in the text?
Which statement accurately describes the virus genome as mentioned in the text?
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What role does DNA play in viruses according to the text?
What role does DNA play in viruses according to the text?
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Study Notes
Origin of Life on Earth
- Africa, a material collected from an asteroid's surface, contains clues about the origin of life on Earth
- Synthesis at deep-sea hydrothermal vents: energy source is chemical gradient, and vent microbes are some of the most primitive living organisms (Archaea)
- Deep ocean was protected from meteorite bombardment and lethal radiation
Synthesis by Destruction
- Energy source: impact from meteorites
- Inorganic molecules in the presence of clay can be converted to organic molecules
Macromolecule Assembly
- Monomers → polymers
- Enzymes are responsible for assembly in cells today, but there's a "chicken-and-egg" problem
- Mineral surfaces such as clay act as catalysts and templates for formation of polymers
- Release of electrons to provide energy to form chemical bonds
- Act as catalysts to speed reactions
- Polypeptides and polynucleotides (RNA molecules) have been linked together on clay surfaces
Reproduction of Macromolecules
- Identical copies of macromolecules are necessary for continuity of life from one generation to the next
- RNA stores information, but some RNA can also act as a catalyst for chemical reactions (ribozymes)
- RNA World hypothesis: a single macromolecule could be both the genetic carrier and the catalyst to copy itself
- Natural selection: best replicators would produce greater numbers in each succeeding generation
System Assembly
- Machinery of life must be separate from its surroundings
- Building blocks are held in higher concentration to facilitate chemical reactions
- Research has shown that fatty acids and other molecules synthesized under prebiotic conditions can form lipid bilayers and spontaneously assemble into enclosed vesicles
- Supports primordial soup hypothesis
Development of Life on Earth
- Hypotheses on the origin of organic compounds:
- Hypothesis 1: Organic molecules were synthesized from inorganic compounds in the atmosphere
- Hypothesis 2: Organic molecules rained down on the Earth from outer space
- Hypothesis 3: Organic molecules were synthesized at hydrothermal vents on the ocean floor
- Hypothesis 4: Organic molecules were synthesized when comets or asteroids struck the early Earth
Oparin-Haldane Hypothesis
- Life arose from inorganic molecules: gradual chemical evolution
- Primordial soup: inorganic molecules + energy = building blocks such as amino acids and nucleotides
- Oxygen-poor atmosphere
- Building blocks combined to form larger, more complex molecules
- Polymers assembled into structures capable of sustaining and replicating themselves
Miller-Urey Experiment
- Tested the Oparin-Haldane hypothesis
- Recreated environmental conditions of early Earth
- Energy source: electricity to simulate lightning
- Produced organic molecules such as amino acids, sugars, and lipids
Exogenous Delivery
- Organic molecules seeded by comets, meteorites, space dust
- Evidence: Meteorite in Australia in 1969 contained dozens of different amino acids
- 3.3 billion year old extraterrestrial organic matter found in sediment in S. Viroids
Conditions on Early Earth
- Almost no atmosphere: volcanic gases such as hydrogen sulfide, methane, and carbon dioxide
- Intense solar radiation
- Strong volcanic activity
- Constant bombardment by meteorites and comets
- History of Earth:
- Earth is ~4.5 billion years old
- Scientists think Earth developed conditions for life ~4.3 billion years ago
- Break in the asteroid bombardment
- Cooler temps allowed condensation to form oceans
- Second round of bombardment ~3.9 billion years ago
- Oldest fossils are ~3.5 billion years old
- Sulfur-metabolizing bacteria
- Life may have evolved multiple times during the billion year gap
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Description
Test your knowledge on viroids - small circles of RNA lacking capsid and envelope, and the conditions on early Earth that influenced the origins of life. Learn about how viroids infect plants and the environmental conditions present during Earth's early stages.
