Origins Of Life Practice Questions Flashcards
Which hypothesis suggests that life on Earth might have originated from extraterrestrial sources?
a) Abiogenesis
b) Panspermia
c) Endosymbiosis
d) Oparin-Haldane
Answer: b) Panspermia
Which of the following conditions simulated by the Miller-Urey experiment was critical for the formation
of organic molecules?
a) High levels of oxygen in the atmosphere
b) Presence of reducing gases like methane and ammonia
c) Absence of water vapor in the experimental setup
d) Constant low temperatures throughout the experiment
Answer: b) Presence of reducing gases like methane and ammonia
Why was early Earth’s atmosphere considered “reducing”?
a) It lacked CO₂.
b) It had high levels of O₂.
c) It lacked O₂, which prevented oxidation of molecules.
d) It contained free radicals.
Answer: c) It lacked O₂, which prevented oxidation of molecules
What makes RNA a strong candidate for the first genetic material?
a) It is more stable than DNA.
b) It can store information and catalyze reactions.
c) It is easier to replicate than DNA.
d) It has more nucleotides than DNA.
Answer: b) It can store information and catalyze reactions.
What are ribozymes?
a) Proteins that catalyze RNA synthesis.
b) RNAs that catalyze reactions.
c) RNAs that store energy.
d) Lipids that help RNA replicate.
Answer: b) RNAs that catalyze reactions.
The transition from RNA to DNA likely occurred because:
a) DNA is more reactive than RNA.
b) DNA is more stable for long-term information storage.
c) DNA catalyzes reactions more efficiently than RNA.
d) RNA cannot form double strands.
Answer: b) DNA is more stable for long-term information storage.
Which environment is thought to be the cradle of life?
a) Volcanic craters
b) Deep-sea alkaline vents
c) Glacier valleys
d) Desert hot springs
Answer: b) Deep-sea alkaline vents
The energy gradient in deep-sea vents is created by:
a) H⁺ ions moving between alkaline and acidic regions.
b) UV radiation heating vent water.
c) Sulfur reacting with oxygen.
d) Lightning striking the vents.
Answer: a) H⁺ ions moving between alkaline and acidic regions.
What role did iron-sulfur clusters in deep-sea vents likely play in the origin of life, and how are they
relevant to modern energy metabolism?
a) Iron-sulfur clusters acted as structural components in early cell membranes and have no modern equivalent
b) Iron-sulfur clusters facilitated early chemical reactions by transferring electrons and are still found in
modern enzymes involved in energy metabolism.
c) Iron-sulfur clusters were the first sources of genetic information and now play a role in RNA synthesis.
d) Iron-sulfur clusters provided a stable environment for early protocells and are now used exclusively in
photosynthesis.
Answer: b) Iron-sulfur clusters facilitated early chemical reactions by transferring electrons and are still
found in modern enzymes involved in energy metabolism.
How do iron-sulfur clusters in modern enzymes relate to pre-biotic chemistry in deep sea alkaline vents?
a) They indicate that life likely originated from volcanic lava flows.
b) They suggest that early life forms used carbon dioxide as their primary energy source.
c) They provide evidence that early biochemical processes may have been catalyzed by minerals similar
to iron-sulfur clusters found in hydrothermal vents.
d) They show that oxygen was abundant in early Earth environments.
Answer: c) They provide evidence that early biochemical processes may have been catalyzed by minerals
similar to iron-sulfur clusters found in hydrothermal vents.
Which of the following was NOT a characteristic of LUCA?
a) DNA→RNA→Protein system.
b) Lipid bilayer membrane.
c) Aerobic metabolism.
d) Ribosomes.
Answer: c) Aerobic metabolism
What type of metabolism did LUCA most likely rely on?
a) Aerobic respiration
b) Anaerobic metabolism using H₂ and CO₂
c) Photosynthesis
d) Fermentation of sugars
Answer: b) Anaerobic metabolism using H₂ and CO₂
LUCA was likely thermophilic, meaning it:
a) Thrived in extreme temperatures.
b) Used sunlight for energy.
c) Required oxygen for survival.
d) Lived in alkaline conditions.
Answer: a) Thrived in extreme temperatures.
Early phototrophs used which molecule for H⁺ ions before switching to water?
a) CO₂
b) H₂S
c) NH₃
d) O₂
Answer: b) H₂S
The Great Oxygenation Event was caused by:
a) Anaerobic respiration.
b) Photosynthesis by cyanobacteria.
c) Deep-sea vent activity.
d) Eukaryotic evolution.
Answer: b) Photosynthesis by cyanobacteria.
