<![CDATA[The research we did at Wiroborang 1 Elementary School, Probolinggo in improving students' critical thinking skills was using the Problem Based Learning (PBL) learning model or problem-based learning. The application that we do using this model is to give students a problem about ecosystem components in Natural Sciences subjects. In this learning model we provide pretest and posttest given before and after learning. The test was carried out with the aim of being able to determine the level of understanding of critical thinking possessed by students. This test was also carried out to compare the results of the scores before and after the material was given to students. The methods used in the observation activities at Wiroborang 1 Elementary School, Probolinggo are qualitative and quantitative methods in the form of delivering material through presentation techniques, question and answer activities, discussion between groups and giving test questions. The results of this study were that students' critical thinking skills increased from a median score of 51.2 to a median score of 66.04, while for the results of giving questions related to the Based Learning learning model that was worked on in groups experienced an increase in the median score of 96. It can be concluded that students at Wiroborang 1 Elementary School, Probolinggo experienced an increase in critical thinking of 19.88% in natural science learning materials related to ecosystem components.]]>
