Biology
Biology: integrating evidence across scales
The Scholarship Biology domain is not defined by a fixed content list in the source; the exam can draw on any Level 3 biological context. It tests whether you can use principles from genetics, evolution, ecology, cell biology and physiology to explain unfamiliar data, evaluate competing models, and connect molecular, organismal and population-level causes. Strong answers show a chain of reasoning, not a named example.
Core rules and concepts
- Treat variation as the raw material of selection: heritable differences plus differential reproductive success change allele frequencies across generations.
- Link structure to function at every scale, and link phenotype to genotype and environment rather than assuming a single gene determines a trait.
- Use feedback and causality: identify inputs, receptors, effectors and outputs in physiological or ecological systems.
- Distinguish timescales: physiological acclimatisation within a lifetime versus evolutionary change between generations.
- Evaluate evidence explicitly: sample size, controls, correlation versus causation, and alternative explanations.
- Use models as tools: state assumptions and limits before applying them to a new organism or ecosystem; a model is not the system.
Worked example
Question: explain why lactase persistence is common in populations with a long history of dairying. Reasoning: the ancestral condition is lactase non-persistence after weaning. A regulatory variant, such as the -13910 T allele in Europeans, maintains lactase expression. In dairying cultures, milk supplies energy and nutrients, so persistent individuals gain a survival/reproductive advantage. Selection raises the variant’s frequency over generations. This is gene–culture coevolution; different populations have independently selected different regulatory variants, so the trait is convergent, not a single global mutation.
Traps that cost marks
Teleology (“evolved to need milk”) replaces mechanism; individual acclimatisation is confused with population evolution; the environment is ignored as a selective filter; data are described but not evaluated; and conclusions exceed the evidence. A claim about a population cannot be supported by a single individual’s response. Always name the selection pressure, the heritable variation and the fitness consequence.