Provide and explain one example of natural selection

For natural selection to occur, four conditions must exist. The first is that the population reprodces enough for there to be competition for resouces and survival between the members. The second is that parents are able to pass on traits through their genes. The third is that there is variation in the traits of members of the population. And the fourth is that this variation in traits affects the chances of survival. The case of a change in the beak size of Galapagos finches on Daphne Major is an example of rapid evolutionary changes explained by natural selection. The finches on the islands showed variation in beak sizes, finches that lived on islands with large seeds had bigger beaks which allowed them to open these seeds, and those that lived on islanands with small seeds had smaller beaks. In 1977 a drought hit the islands which resulted in plants producing larger and tougher seeds. Finches with small beaks could not eat these seeds and starved and died before being able to reproduce, while finches with big beaks survived and reproduced to create finches who also had large beaks. And so due to natural selection, the average beak size of the finches increased.