DemosthenesPer disputationem veritatem quaerimus
Demosthenes/Notes/A-level Biology

AQA · free revision notes

A-level Biology notes

Notes for every topic on the A-level Biology — AQA route specification, with worked examples and key equations. Free to read; create an account to practise each topic with exam questions and timed papers.

  1. Biological moleculesAlmost everything else in this course is downstream of this topic. Four classes of large molecule — carbohydrates, lipids, proteins and…
  2. CellsThis topic moves from the molecules of AB1 to the structures they build. Two ideas hold the whole topic together. First, structure and…
  3. Exchange with the environmentOne relationship runs underneath every subtopic here: rate of diffusion is proportional to surface area and to concentration difference,…
  4. Genetic information and variationThis topic follows one chain from a gene's physical existence on a chromosome to the diversity it makes possible. DNA is organised into…
  5. Energy transfersTwo of the same underlying mechanisms recur throughout this topic, once in each direction. Chemiosmosis — an electron transport chain…
  6. Responses and coordinationEvery subtopic here is a variation on the same three-part control loop — receptor, coordinator, effector — running at a different scale: a…
  7. Populations, evolution and ecosystemsThis topic follows genetic variation upward in scale, from a single cross between two individuals, through the allele frequencies of a…
  8. Control of gene expressionEvery earlier topic in this course treated 'has a gene' and 'expresses a gene' as roughly the same thing; this topic is about everywhere…