Evolution and Adaptation
This domain covers natural selection, adaptation, evidence for evolution and speciation. The exam asks you to explain changes in allele frequency and to avoid Lamarckian reasoning.
Natural selection
Populations show variation caused by mutations and sexual reproduction. Competition for resources means some variants survive and reproduce more successfully. Their alleles become more frequent in later generations. Evidence includes fossils, comparative anatomy and DNA sequences.
Adaptation and speciation
Adaptations can be anatomical, physiological or behavioural. Speciation occurs when populations become isolated, experience different selection pressures, and accumulate differences until they can no longer interbreed. Antibiotic resistance is natural selection in action.
Worked example
A bacterial population is exposed to an antibiotic. A few bacteria carry a mutation giving resistance. They survive, reproduce, and pass the resistance allele to offspring. Over generations, the proportion of resistant bacteria rises. Reasoning: the antibiotic selects existing variation; it does not create resistance in individual bacteria.
Traps
- Individual organisms do not evolve during their lifetime.
- Acquired characteristics, such as a builder's muscles, are not inherited.
- 'Survival of the fittest' means reproductive success, not physical strength.