The present study elaborates on a domain-specific approach to NOS (Nature Of Science) and employs a NOTSs (Nature Of The Sciences) agenda to investigate how Greek in-service physics teachers understand the unique features of school physics and biology. Our theoretical framework focuses on the notion of worldview and important differences that exist between the Newtonian and the neo-Darwinian worldviews, whereas our methodology involves questionnaires and mainly individual interviews. The empirical findings indicate that participants understand the nature of the sciences from the perspective of how they understand their own science and tend to share homogeneous NOTSs conceptions that mostly stem from how they have assimilated positivistic tenets. As a result, they have serious misunderstandings regarding (a) the nature of biology because they project upon biology epistemological characteristics that biology does not possess and (b) several NOS items because they erroneously consider domain-specific NOS (or NOTSs) conceptions to be domain-general and disregard important NOTSs conceptions that underpin the understanding of domain-general NOS items. The implications of all such findings for synergies that may exist between the NOTSs agenda and the current domain-general approach to NOS are also discussed.