27 exam-style questions on Origins of cells — topic A2.1 of Unity and diversity in the IB Biology syllabus — with answers and explanations. Samples below; the full set is free with an account.
State what the Miller–Urey experiment (1953) provided evidence for.
Answer: Amino acids can form spontaneously under early-Earth conditions
Passing sparks through a reducing gas mixture yielded amino acids, showing organic monomers could form abiotically; it did not create life or free oxygen.
In the RNA world hypothesis, RNA is proposed as the first genetic material mainly because RNA can:
Answer: store genetic information and catalyse reactions
RNA can act as both a heritable template and a catalyst (ribozyme), so it could support early self-replication before DNA and proteins specialised.
Which observation best supports the endosymbiotic origin of mitochondria?
Answer: Mitochondria have 70S ribosomes and circular DNA
Prokaryote-type 70S ribosomes and a small circular chromosome resemble free-living bacteria, consistent with mitochondria descending from an engulfed prokaryote.
The last universal common ancestor (LUCA) is best described as:
Answer: the ancestor of all living things
LUCA is the inferred common ancestor of all living organisms, evidenced by shared features such as the genetic code and core metabolism.
State what a ribozyme is.
Answer: an RNA molecule that acts as a catalyst
Ribozymes are catalytic RNA molecules; their existence supports the idea that RNA could catalyse reactions in early life before protein enzymes.
Membrane-bound droplets that form spontaneously when phospholipids are mixed with water and are used as models for the first cells are called:
Answer: protobionts
Phospholipids self-assemble into bilayer vesicles (protobionts), providing a compartment that concentrates molecules — a plausible precursor to the first cells.
That was 6 of 27 Origins of cells questions.
Practise all 27 freeStateAO1 · 1–2 marks
One word or one short sentence. No explanation, no working: the mark is for the fact itself.
OutlineAO2 · 1–4 marks
A brief account or summary: the main points in two or three sentences, no evaluation.
ListAO1 · 1–2 marks
Give the items only, one per line. Extra description earns nothing and costs time.
27 Origins of cells questions — free with an account. Spaced repetition, streaks and full exam simulations included.
Practise them freeThis platform is independently developed and is not endorsed by, affiliated with, or sponsored by the International Baccalaureate Organization. “International Baccalaureate” and “IB” are registered trademarks of the IBO.