Marcel Weber (1999) argued that the principle of competitive exclusion is a law of ecology that could explain phenomena (1) by direct application, or (2) by describing default states. Since he did not offer an account of explanation by direct application of laws, I offer an interpretation of explanation by direct application of laws based on a proposal by Elgin and Sober (2002). I show that in both cases it is the descriptions of mechanisms that explain phenomena, and not the laws. Lev Ginzburg and Mark Colyvan (2004) argued Malthus’ Law of Exponential Growth is the first law of ecology, and that its role explanations is to describe default states. I argue the role of the descriptor of default states is not necessary for ecological explanations, and the descriptions of underlying mechanisms offer the required explanations. Additionally, I examine the possibility not considered by Ginzburg and Colyvan that Malthus’ law could explain the phenomena of exponential growth by direct application. I also show that this explanation is inferior to the descriptions of underlying mechanisms.