What is one characteristic that evolution acts on?

Evolution acts on heritable characteristics of populations because these traits are passed from one generation to the next through genetic material. Heritable characteristics can be influenced by natural selection, genetic drift, mutation, and gene flow. By favoring traits that enhance survival and reproduction, evolution can lead to changes in the frequency of these traits within a population over time.

The other options do not directly represent what evolution targets. The physical environment can influence which traits are favorable, but it is not a characteristic that evolves itself. Similarly, the behaviors of animals can be influenced by evolution, but it is primarily the genetic basis of those behaviors that is acted upon through evolutionary processes. The historical context of life forms provides background on how they evolved but does not itself represent a characteristic subject to evolutionary change. Therefore, heritable characteristics are the core elements on which evolutionary forces operate.