 So, if the proper way to understand natural selection casts organisms as the units of selection, and species as the unit of evolution, then Gould and Eldredge’s model of PE challenges that view. Alternatively, if the proper way to understand natural selection merely names biological individuals as the units of selection and biological populations as the unit of evolution, and species can be biological individuals too, then Gould and Eldredge’s model of PE is not really a challenge to the model of natural selection, it is just a new instance of it. This is because the notion of  biological individual (see entry)  is more expansive than that of biological organism; biological individuals include but are not limited to biological organisms. Biofilms, coral reefs, insect colonies, obligate symbionts, siphonophores, slime molds, and viruses are just a few of the many biological entities that we might want to consider as individuals, although they are not organisms (see Buss 1983; J. Wilson 1999; Clarke 2010, 2013; and R.A. Wilson &amp; Barker 2013, among others). If species are themselves individuals (Ghiselin 1974; Hull 1976), then the traditional evolutionary theorist may be able to accommodate species-level selection—in this sense, it is just another flavor of individual-level selection. Note that is it is very easy for this dispute to become an instance of what the philosopher John Beatty (1997) calls a “relative significance” debate—one in which proponents move from arguing about whether something is possible (species acting as the unit of selection) to whether that thing is significant (as opposed to a mere oddity).