Long necks in giraffes are an example of a trait that has been naturally selected over the evolutionary history of an organism. Which of the following best explains what must have happened for this selection to occur? In each generation of giraffes, long-necked giraffes mated only with short-necked giraffes.
In each generation of giraffes, all the neck lengths were the same, and all the long-necked generations survived.
In each generation of giraffes, there was an abundance of resources available for each individual.
In each generation of giraffes, there was variation in neck lengths, and scarcity of resources meant that not all giraffes survived.