Nick, who is 13, regularly drinks beer with three friends of the same age. How much more likely are they to become dependent on alcohol than if they had waited for another eight or nine years before they started drinking?

Natural selection involves changes in the genetic makeup of a population over a period of time. the random change of dna from parent to offspring, called mutations, can produce variations in offspring. some mutations can be , while others can be harmful. in this experiment, students modeled random mutations. data was collected to determine if the mutations were or harmful when trying to collect and eat food.