Cracking the AP Biology Exam


Diversity of Organisms


Man has long been aware of the diversity of life, but figuring out exactly how organisms are related to one another took some work. Early scientists agreed that many creatures shared common features. However, there was little agreement about how all organisms were related to one another, if at all!

Interestingly, our means of classifying organisms is essentially the same as that used by those earliest scientists: We order organisms into groups on the basis of shared characteristics or traits. The major difference between our approach and that of early biologists is that we now know that such traits are acquired over the long process of evolution. Consequently, we group animals together on the basis of evolutionary relatedness, and not simple appearance. These relations are manifested in traits, and the sum of these traits is known as phylogeny. The science of classifying animals according to their phylogeny is known as taxonomy.