Evolution and Diversity of Life
What this domain tests
Evolution and Diversity of Life asks you to explain how populations change over time and how living diversity arose. Expect natural selection, evidence for evolution, common ancestry, speciation, phylogeny, and the roles of genetic drift, gene flow, and mutation. Questions often ask you to interpret a scenario or cladogram rather than recall a definition.
Core rules
- Natural selection requires variation, heritability, and differential reproductive success.
- Individuals do not evolve; populations evolve as allele frequencies change across generations.
- Mutations and recombination create new genetic variation; selection, drift, and gene flow change its frequency.
- Evidence includes fossils, homologous structures, embryology, biogeography, and molecular similarities.
- Speciation occurs when populations become reproductively isolated and diverge.
- Phylogenies show common ancestry; homologous structures reflect shared ancestry, while analogous structures reflect similar function without close ancestry.
Worked example
A bacterial population is exposed to an antibiotic. A few cells carry a mutation that reduces drug binding. After treatment, those cells survive and reproduce, and the population becomes mostly resistant. Reasoning: The mutation existed before exposure; the antibiotic did not create it. The antibiotic acts as a selective pressure: resistant cells have higher fitness and leave more offspring. Over generations, the frequency of the resistance allele increases. This is directional selection, not individual adaptation during exposure.
Traps
- Writing that bacteria “learn” or “adapt” to the drug; resistance is inherited variation.
- Claiming natural selection creates variation; it acts on existing variation.
- Treating “fittest” as strongest; fitness means reproductive success in a given environment.
- Confusing homologous and analogous structures.