HL Pre-class: A2.1.3— Challenge of explaining the spontaneous...

The principle that “all cells come from pre-existing cells” seems to conflict with the idea of abiogenesis. How do scientists reconcile this?

• Abiogenesis describes an ongoing process that still happens today.

• Abiogenesis explains how the first cells formed before cell division existed.

• Abiogenesis means all cells arose directly from LUCA.

• Abiogenesis shows that the first cells formed from fossilized protocells.

LUCA (the Last Universal Common Ancestor) is described as:

• The very first protocell formed by abiogenesis.

• The only ancestor of humans, not other organisms.

• A descendant of earlier protocells that arose through abiogenesis.

• A cell that lived 750 million years before Earth formed.

Why would the lack of oxygen in Earth’s early atmosphere have been essential for abiogenesis?

• Oxygen would have immediately fossilized protocells.

• Oxygen would have blocked volcanic gases from forming.

• Oxygen would have broken down organic molecules before they could accumulate.

• Oxygen would have lowered surface temperatures, preventing polymerization.

Which of the following best illustrates compartmentalization as a step toward the first cells?

• Ribozymes catalyzing their own replication.

• Fatty acids forming vesicles with internal chemistry distinct from the environment.

• Amino acids forming spontaneously in the Miller–Urey experiment.

• Monomers linking together to form RNA polymers.

Why do linked scientific models, such as the Miller–Urey experiment and protocell studies, strengthen the plausibility of abiogenesis?

• Because they show protocells must have fossilized.

• Because they demonstrate multiple processes that together could form living systems.

• Because they confirm abiogenesis is the only possible explanation.

• Because they reproduce the exact historical conditions of early Earth.

Which of the following describes a limitation of scientific models when studying abiogenesis?

• Models cannot be used to test scientific claims.

• Models always provide absolute proof of natural processes.

• Models cannot capture every detail and depend on assumptions about early Earth.

• Models are useless unless they perfectly replicate early Earth conditions.

If early Earth had contained oxygen from the start, which step in abiogenesis would most likely have been prevented?

• Assembly of polymers into larger macromolecules.

• Compartmentalization into membrane vesicles.

• Synthesis of simple organic molecules from inorganic precursors.

• Replication of ribozymes in an RNA world.

Why is studying the spontaneous origin of cells considered more difficult than studying cell division today?

• Cell division cannot be recreated in modern laboratories.

• Scientists are unsure if LUCA ever existed.

• Protocells formed too recently to leave reliable evidence.

• Early protocells left no fossils, and early Earth conditions cannot be fully replicated.

Which of the following best explains why experiments like Miller–Urey are still important, even though they cannot prove exactly how life began?

• They allow scientists to perfectly reconstruct ancient protocells.

• They demonstrate that LUCA was the first protocell.

• They provide indirect evidence by testing plausible pathways for abiogenesis.

• They eliminate all uncertainty about early Earth’s conditions.

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