Explain how different tortoises developed on different islands with regards to evolution & natural selection.

On the island there is competition for lower lying grasses and no competition for higher bushes.Because of natural variation some tortoises have longer necks, which enables them to reach the higher bushes on island 2. Therefore, they have an advantageous mutation and they become stronger because they are better adapted and so are more likely able to reproduce effectively. Those offspring with the same mutation are at an advantage and so become bigger and stronger again. This adaptation, is advantageous and those with longer necks thrive. The adaptation is selected for. This happens until the being long-necked allele is selected for, and so it becomes a dominant allele.