In this new context concept approach, field research on the Trinidadian guppy is used as an appealing example of evolutionary change in populations. Pupils are asked to investigate the underlying mechanisms. In doing so, defects in their knowledge are revealed, in particular the role of meiosis in creating genetic variation. The reason for these defects is probably the incomplete explanation of meiosis and mitosis during class. Whereas mitosis is aimed at the strict conservation of genetic information, the process of meiosis results in the creation of genetic variability by the independent assortment of chromosomes. Once corrected, pupils gain a better insight into the relevant integration levels of biology, such as that processes at a cell level reveal themselves during natural selection and lead to changes in the phenotype of the population. The importance of sexual reproduction for evolutionary change also becomes clearer to the pupils.