Explain the theory of chemical evolution and the experiment that supports it.

1. 1 · Define in one line. Chemical evolution says life formed slowly from simple chemicals on the early Earth. It was given by Oparin (1924) and Haldane (1929).
2. 2 · Describe the early Earth. Very hot; a reducing atmosphere of CH₄, NH₃, H₂ and water vapour; no free oxygen; energy from lightning, UV rays and volcanoes.
3. 3 · Write the stages.
   • Gases → simple organic molecules (amino acids, sugars, bases)
   • Collected in the sea as the primordial soup
   • Joined into proteins and nucleic acids
   • Wrapped as coacervates → first simple cells
4. 4 · Explain the Miller and Urey experiment (1953). Gases and water vapour in a closed apparatus; electric sparks as lightning; a condenser cooled the gases; amino acids collected in the trap after about a week.
5. 5 · Draw the apparatus. Boiling flask, large gas flask with electrodes, condenser and U-tube trap. Label the gases, the spark and the amino acids.
6. 6 · Link to daily life. These amino acids are the same building blocks of protein that we get from dal, milk and eggs.
7. 7 · Close in one line. So organic molecules can form from inorganic ones, which supports chemical evolution.

Scoring tip: Write all four gases with their formulas and name one amino acid (glycine). A neat labelled apparatus earns marks.