ABSTRAKPenelitian ini bertujuan untuk mengetahui peningkatan penguasaan konsep siswa MA kelas X setelah digunakannya penugasan fenetik melalui lembar kerja siswa. Metode penelitian yang digunakan adalah weak experiment dengan desain penelitian One-Group Pretest-Posttest Design. Data peningkatan penguasaan konsep siswa diperoleh melalui selisih atau gain skor posstest dan pretest, yang kemudian dihitung gain ternormalisasinya. Respon siswa dan guru tentang penggunaan penugasan fenetik melalui LKS dijaring melalui angket siswa dan wawancara guru. Sampel penelitian adalah kelas X-A di Madrasah Aliyah Darul Arqam Garut tahun pelajaran 2009/2010. Hasil penelitian menunjukan bahwa terdapat pengaruh penugasan fenetik melalui LKS terhadap penguasaan konsep pada keanekaragaman hayati yang diketahui dengan adanya peningkatan penguasaan konsep dengan nilai gain ternormalisasi 0,306 yang berkategori sedang.ABSTRACTThis study aims to determine the increase in students' mastery of concepts MA class X after using phenetic assignment through student worksheets. The research method used was weak study design experiment with OneGroup Pretest-Posttest Design. Data of the increasing students' mastery of concepts was obtained by difference or gain scores posstest and pretest, which was further calculated its normalized-gain. The response of students and teachers on phenetic assignment through worksheets were captured through student questionnaire and teacher interviews. The research sample was XA classes at Madrasah Aliyah Garut Darul Arqam school year 2009/2010. The results showed that there is an influence phenetic assignment through the mastery of concepts worksheets on biodiversity of seed plant as the increasing of concept’s mastery with normalized-gain value 0.306 , which is categorized as moderate.