The diagram shows the impact of birds feeding on a population of beetles over time - HSC - SSCE Biology - Question 3 - 2019 - Paper 1

The change in the beetle population can be attributed to Environmental pressure. In this context, the birds represent a selection pressure on the beetle population, affecting their survival and reproduction. As the birds prey on the beetles, those with traits that make them less detectable or less palatable will have a higher chance of surviving and passing on their genes. This process illustrates natural selection, where environmental factors influence the survival of species over time.