ABSTRAK
Tujuan penelitian adalah untuk meningkatkan kemampuan argumentasi  tertulis siswa kelas X MIPA 2 SMA Negeri 5 Surakarta pada materi Ekosistem melalui penerapan project based learning.
Penelitian yang dilakukan termasuk penelitian tindakan kelas (PTK) yang terdiri dari 3 siklus dan pada masing-masing siklus terdiri dari 4 tahap, yaitu perencanaan, tindakan, observasi, dan refleksi. Subjek penelitian adalah siswa kelas X MIPA 2 SMA Negeri 5 Surakarta yang berjumlah 30 siswa. Data diperoleh melalui tes, observasi, dan dokumentasi. Validasi data menggunakan triangulasi teknik. Analisis data dilakukan dengan teknik deskriptif kualitatif. Prosedur penelitian menggunakan metode spiral, yang terdiri dari empat tahap kegiatan, yaitu: perencanaan, tindakan, observasi, dan refleksi.
Hasil penelitian menunjukan penerapan project based learning meningkatkan kemampuan argumentasi tertulis siswa pada materi Ekosistem. Kemampuan argumentasi tertulis siswa mengalami peningkatan secara fluktuatif. Kemampuan argumentasi tertulis siswa pada Pra-Siklus sebesar 22,04%, pada Siklus I sebesar 30,48%, pada Siklus II sebesar 25,74%, dan pada Siklus III sebesar 32,01%. Kemampuan stgumentasi tertulis setiap siswa pada akhir siklus menglami peningkatan dari Pra-Siklus.
Kesimpulan penelitian adalah penerapan project based learning meningkatkan kemampuan argumentasi tertulis siswa kelas X MIPA 2 SMA Negeri 5 Surakarta pada materi Ekosistem.
Kata Kunci: Project Based Learning, Argumentasi Tertulis.
ABSTRACT
The objectives of this research was to improve students written argumentation skill on Ecosystem material in class X Science 2 SMA Negeri 5 Surakarta through the aplication of projcet based learning. This research was a class room action research conducted in three cycle. The subject of this research was students in X Science 2 of SMA Negeri 5 Surakarta academic years 2014/2015 that are 30 students. Data of this research were obtained from the test, observation, and documentation. Data validation of this research was triangulation method. This research was descriptive qualitative research which was analyzed through three component analysis: data reduction, data presentation, and taking the conclusion or verification. This research uses spiral model that consists of 4 stages, namely: planning, action, observing, and reflecting.
Results of this research shows that the aplication of project based learning improved students written argumentation skill. Students written argumentation skill were 22,04% in the precycle, 30,48% in the  first cycle, 25,74% in the second cycle, and 32,01% in the third cycle.
The research conclution was the implemantation of project based learning improved students written argumentation skill on Ecosystem material in class X Science 2 SMA Negeri 5 Surakarta.
Keywords: Project Based Learning,  Written Argumentation