Question

During a conversation at the dinner table, a high school student tells his mother that, "At first all giraffes had short necks because they all ate leaves close to the ground, but when all those leaves were gone some giraffes started being born with long necks".
Which statement would be most helpful for the student to understand the concept?

• A. Phenotypic variations occur through random mutations which are then selected for or against.
• B. The phenotype for neck length changed in giraffes so that the species did not go extinct.
• C. Short-necked giraffes developed long necks in response to increased competition for food.
• D. When the environment changed, the struggle to exist created new mutations in the gene pool and natural selection acted on them.

Answer 1

The correct option is D When the environment changed, the struggle to exist created new mutations in the gene pool and natural selection acted on them.

For the giraffes, the change in the position of the food (leaves) from near to ground level to higher on the trees, triggered for adaptation to prevent extinction. So, those giraffes that underwent genetic changes/variations and developed long necks were able to obtain food and survive in the changed environmental conditions, while others perished, as this change in the genetic pool was beneficial for the giraffes propagation. It was passed on to next generation and so the modern day giraffe has long necks.