The EFFECT OF PROBLEM-BASED LEARNING MODEL ON STUDENTS’ SCIENCE LITERACY SKILLS IN CLASS VII ECOLOGY MATERIAL IN PUBLIC JUNIOR HIGH SCHOOL 27 MEDAN. universe [Internet]. 2024 Sep. 17 [cited 2026 Aug. 13];5(1):122-33. Available from: http://universe.ppj.unp.ac.id/index.php/universe/article/view/924