I have been teaching science since 1981. What differentiates teaching this discipline from others is that it must be hands-on as often as feasible to illustrate concepts that may be difficult to explain verbally or by reading text. The most meaningful learning takes place when students apply the concepts they learned in an experiment. Therefore, although teachers in all areas need to differentiate their lessons in terms of the type of learners they have in their classrooms-auditory, verbally, kinestheically, etc, in science, it is extremely meaningful when students can do trial and error learning, and come to their own conclusions about a concept from the curriculum.
I think that teachers of Science might point to the fact that the field of Science is so indepth each subsection could constitute its own field. For example, teachers of Algebra can cross over into Geometry with relative ease. Students can see how closely related the concepts are. Grammar and writing are elements that students can see as different, but linked with one another. Yet, students in scientific rigor would have to see fields such as Biology, Chemistry, and Physics in the course of a year. Each unit is so indepth that it can represent its own lifetime in study. For Science teachers, this is a condition that makes their own discipline uniquely different from others.
Another reason why Science teachers might feel that their subject is more distinctive than other subjects would be in the laboratory inquiry presence. In the end, students engaged in the process of learning through labs have to activate a sense of inquiry to a greater degree than perhaps other courses which are more linear in terms of developing student understanding. For science teachers, the "light bulb" moment or that "A-Ha" moment, what is seen as the Archimedes envisioning of "Eureka!," is something that lies dormant within the student, but which is something that the competent science teacher seeks to evoke from their children. As any science teacher can tell you, this is tough and fundamentally different than other subjects.
In good conscience, I think that it should be noted that there might not be an answer to such a question. History teachers will find a set a factors that make teaching their subject different than anyone else. Their colleagues who teach English will find a bevy of reasons why their subject is differentiated from others and their next door Math colleagues will not relent in how there are a multiplicity of factors that make their courses fundamentally different than others. In the end, every teacher will find a set of factors that differentiate their subject's teaching from another. Two questions arise from this condition. The first is what is really gained when we live in an academic world that prevents a full embrace of interdisciplinarity and the second is what agenda is being advocated by the division of content teaching into specific differentiating factors.