The principle aim of this project is to determine the effect of a teaching didactic unit with the topic of the circulation in human beings to the development of argumentative ability in the third grade students of the College to Jose Antonio Galan of the city of Pereira. The starting point of the research hypothesis is given by the implementation of a teaching didactic unit, based on young scientific methodology that is based on the inquiry, collaborative work, the experiences of observation, the use of scientific tools and records. Through this is tool is expected to improve and develop the argumentative ability in the third grade students of the College to Jose Antonio Galan of the city of Pereira. This research is based on the quantitative approach of quasi-experimental with a constructive perspective of education, which allowed facilitating the learning processes of students. Therefore, this project developed a didactic teaching unit following the parameters of the young scientists program, which displays significant strategies for teaching science, the proposal enters the development of the following elements of the argumentation: justification, data or evidence, conclusion and also basic knowledge, the project seeks to identify the initial level of the argumentative capacity in students through a pre-test, which will allow to design and implement a didactic unit in taking into account the necessities about the concept of movement and finally through a post-test to analyze the changes in the level of argumentation. The results of these instruments were organized and systematized in Excel, through charts and graphs, and then made a detailed analysis of individual (per student) as a general form. Finally, there was a contrast of the results, both in the post-test as in the pre-test. This project has a theoretical and conceptual support and based on the teaching of science, argumentation, Small Scientists program, standardized tests and KNOW TIMMS and circulation in human beings. At the end of this research we can conclude that the teaching didactic unit achieved a major impact on the development of argumentative ability inasmuch as students initially applied only some elements of the argument, however, the implementation of the post-test could evidence the significant advance in each of the components of this.