Explain the Oparin-Haldane theory of the origin of life and describe the experiment that supported it.
How to lay out the answer. Follow the frame, then write it in your own words.
1 · State the theory in one line. Oparin and Haldane proposed that the first life arose from non-living organic molecules, formed earlier by chemical evolution from inorganic substances.
2 · Describe the early Earth.
High temperature, volcanic storms and lightning.
Reducing atmosphere with CH₄, NH₃, H₂ and water vapour, and no free oxygen.
3 · Give the sequence. Inorganic gases, then simple organic molecules (amino acids, sugars, bases), then giant molecules, then non-cellular life (about 3 billion years ago), then the first cells (about 2 billion years ago).
4 · Describe Miller's experiment. Closed flask with CH₄, H₂, NH₃ and water vapour at 800 °C, electric discharge, condenser; amino acids formed.
5 · Draw Miller's apparatus. [Diagram: spark chamber with electrodes, gases, condenser, trap with organic compounds, boiling water flask]
6 · Add the extra evidence. Others obtained sugars, nitrogen bases, pigments and fats; meteorites contain similar compounds.
7 · Close in one line. So life most likely began by chemical evolution followed by biological evolution.
Scoring tip: Name both scientists and write the four gases and 800 °C exactly. A labelled apparatus earns a separate mark.
