page 11 21. In three-spined stickleback fish, males have a distinctive red underside in the breeding season, which is not present in females. Territorial males were presented with model fish, some of which had their undersides painted red and some of which were left unpainted. Males showed an automatic attack response to only the red-painted models. This attack response behaviour is triggered by A sexual dimorphism B sexual selection C an honest signal D a sign stimulus. 22. The list shows three events in meiosis I. Q Independent assortment R Recombination of alleles of linked genes S Pairing of homologous chromosomes The order in which these events occur is A S – R – Q B S – Q – R C Q – R – S D Q – S – R. [Turn over