In the diagram, the change in the length of the neck of the giraffes shown was brought about by

The change in the length of the neck of the giraffes shown in the diagram was brought about by natural selection. Over time, giraffes with longer necks were better able to reach food sources that were higher up in trees, giving them a survival advantage over giraffes with shorter necks. These longer-necked giraffes were then more likely to survive and reproduce, passing on their longer-necked traits to their offspring. This process of natural selection gradually led to the evolution of longer necks in giraffes over many generations. Geographical isolation, predation, and symbiosis may also play a role in evolution, but in this particular case, the lengthening of the giraffe necks was primarily driven by natural selection.