A-level Biology Key Concepts

Short explainers of the ideas that come up again and again in A-level Biology exams. Start here if a topic isn't clicking.

Molecules and cells

Polar and charged molecules
Surface area to volume ratio
Mitosis and the cell cycle

Transport and physiology

Haemoglobin and the Bohr effect
How to read a spirometer trace
Plant responses

Maths and practical skills

Independent and dependent variables
Averages, range and standard deviation

Genetics and ecology

Hardy-Weinberg calculations
Autosomal linkage, epistasis and chi-squared
The nitrogen cycle