Studies have shown that in their study of biology, students perceive genetics and ecology to be difficult areas to learn. This has translated into rote learning of genetics and ecological concepts and reflected in poor performance in tests involving these concepts. Considering the importance of genetics and ecology to man's understanding of himself and his environment, there is a need to inquire into ways of ensuring that students attain meaningful learning of genetics and ecology rather than learning by rote. The efficacy of the concept-mapping strategy was tried out in this study with 138 predegree biology students. The results showed that the 63 students in the experimental group who employed the concept-mapping technique performed significantly better on the test of meaningful learning in genetics, t(136) = 16.01. p < 0.001, and ecology, t(136) = 12.27, p < 0.001, than their control group counterparts (N = 75). The implications of these results for teacher education in biology are addressed in the article.