Evolution — common mistakes

For Paper 4, remember that evolution questions often require you to explain processes rather than just defining terms. When describing natural selection or speciation, ensure you link genetic variation, selection pressures, differential survival/reproduction, and changes in allele frequencies over time. For Hardy-Weinberg, always show your working clearly and state what each calculated value represents.

For Cambridge A-Level Biology 9700 topic 17.3, Evolution covers key concepts like natural selection (directional, stabilising, disruptive), the sources of genetic variation, allopatric and sympatric speciation, the Hardy-Weinberg principle for allele and genotype frequencies, and the impact of genetic drift on populations.

To ace Paper 4 Evolution questions, focus on explaining the mechanisms and interconnections between concepts. Don't just list facts; describe the sequence of events in natural selection, the roles of isolation in speciation, and the assumptions of Hardy-Weinberg. Practise applying formulas and interpreting graphs.

Natural selection is a non-random process where individuals with advantageous traits are more likely to survive and reproduce, leading to adaptations. Genetic drift, however, is a random process of allele frequency change due to chance events, particularly significant in small populations. While both alter allele frequencies, only natural selection leads to adaptation.