<![CDATA[This research aimed to know the influence of discovery learning towards studentss critical thinking skill and learning activity on immune system subject matter. The samples were student on 11th grade of Science 3 and Science 2 in SMAN 1 Seputih Surabaya. The design was pretest-posttest non equivalent. The quantitative were obtained from studentss critical thinking skill that was analyzed by t-test and U-test with signification level of 5%. The learning activity and studentss perception were analyzed descriptively. The result showed that N-gain on experiment class was 42,72 which was higher than control class that was 34,01. Beside that, the students learning activity on experiment class was 77,78% which was also higher than control class that was 60,00%. Based on this research, it can be concluded that discovery learning model gave influence towards critical thinking skill and students learning activity on immune system subject matter.Penelitian ini bertujuan untuk mengetahui pengaruh Discovery Learning terhadap KBK dan aktivitas belajar siswa pada materi sistem pertahanan tubuh. Sample berupa kelas XI IPA3 dan XI IPA2 SMAN 1 Seputih Surabaya. Desain penelitian yaitu pretest-posttest non equivalent. Data kuantitatif berupa KBK siswa yang dianalisis menggunakan uji t dan U dengan taraf signifi-kansi 5%. Sementara data aktivitas belajar dan tanggapan siswa dianalisis secara deskriptif. Hasil penelitian menunjukkan N-gain siswa kelas eksperimen (42,72) lebih tinggi dan berbeda signifikan dibanding kelas kontrol (34,01). Aktivitas belajar siswa kelas eksperimen (77,78%) juga lebih tinggi daripada kelas kontrol (60,00%). Berdasarkan hasil penelitian, dapat disimpulkan bahwa model Discovery Learning berpengaruh signifikan terhadap KBK dan aktivitas belajar siswa pada materi sistem pertahanan tubuh.Kata kunci: aktivitas belajar, discovery learning, keterampilan berpikir kritis]]>
