Biology HL
Origins of Cellular Life
- 1.
A hypothetical sealed apparatus circulates water vapour and a gas mixture through an electrical discharge. Organic molecules appear after several days. A matched apparatus without the discharge produces far fewer. Explain the role of the comparison and evaluate the claim that the experiment has created living cells and proved the exact origin of life on Earth.
[4 marks] · no calculator - 2.
Fatty acids in water can assemble into membrane-bounded vesicles. Explain why this is a plausible step towards the origin of cells, and give two additional capabilities needed before a vesicle population could undergo sustained Darwinian evolution.
[4 marks] · no calculator - 3.
Explain why RNA is a candidate for an early hereditary molecule. Then explain how widespread use of the same genetic code supports common ancestry, without implying that the last universal common ancestor was necessarily the first life ever to arise.
[4 marks] · no calculator - 4.
In a hypothetical experiment, fatty acids form vesicles in water. A fluorescent solute is initially trapped inside some vesicles but gradually appears outside. Explain how this result supports compartment formation but does not demonstrate a fully living cell. Suggest a control for leakage from the vesicles.
[4 marks] · no calculator - 5.
A hypothetical RNA molecule catalyses a reaction in a laboratory but cannot copy itself under the tested conditions. Explain why catalytic RNA is relevant to an RNA-world hypothesis and why this result alone cannot establish how the first self-replicating system arose.
[3 marks] · no calculator