Hardy-Weinberg equation, mutation & natural selection (Edexcel Int. A-level Biology)

This lesson describes how the Hardy-Weinberg equation can identify changes in allele frequency that can be the result of mutation and natural selection. The detailed PowerPoint and accompanying resources have been designed to cover points 4.20 (i) & (ii) of the Edexcel International A-level Biology specification

The lesson begins with a focus on the equation to ensure that the students understand the meaning of each of the terms. The recessive condition, cystic fibrosis, is used as an example so that students can start to apply their knowledge and assess whether they understand which genotypes go with which term. Moving forwards, a step-by-step guide is used to show students how to answer a question. Tips are given during the guide so that common misconceptions and mistakes are addressed immediately and then students are given the opportunity to apply their knowledge to a set of 3 questions, which have been differentiated so that all abilities are able to access the work and be challenged

The rest of the lesson focuses on describing how the mutations which create the variation needed for natural selection to occur can be given as reasons for any change in allele frequency. 2 quick quiz competitions are used to introduce MRSA and then to get the students to recognise that they can use this abbreviation to remind them to use mutation, reproduce, selection (and survive) and allele in their descriptions of evolution through natural selection. The main task of the lesson challenges the students to form a description that explains how this strain of bacteria developed resistance to methicillin to enable them to see the principles of natural selection. This can then be used when describing how the anatomy of the modern-day giraffe has evolved over time.