Evolution and Origin of Life
This domain covers origin-of-life hypotheses, evidence for evolution, natural selection, population genetics, speciation and human evolution.
Core rules
- Oparin and Haldane proposed chemical evolution; Miller and Urey produced amino acids from simple gases and electric discharge.
- The RNA world hypothesis suggests RNA was both genetic material and catalyst before DNA and proteins.
- Evidence includes fossils, homologous organs, analogous organs, biogeography and molecular similarities.
- Natural selection acts on phenotypic variation in a population; individuals do not evolve.
- Hardy-Weinberg equilibrium requires no mutation, no migration, no selection, random mating and large population size.
Worked example
A recessive disease affects 1 in 10,000 people. If the population is in Hardy-Weinberg equilibrium, q^2 = 0.0001, so q = 0.01 and p = 0.99. Carrier frequency is 2pq = 2 x 0.99 x 0.01 = 0.0198, or about 2%. The calculation shows why a rare recessive disease can still have many carriers.
Traps
- Natural selection acts on phenotypes, not directly on genes.
- Analogous structures indicate convergent evolution, not common ancestry.
- Genetic drift is random and matters most in small populations.
- Hardy-Weinberg describes an ideal equilibrium, not a universal law.