On the basis of previous lexical bundle studies, this paper examines the forms, structures and functions of 4-word bundles in a corpus of textbooks and a corpus of research articles in Biology. The study includes the main biological disciplines and focuses on three major features: the overall distribution of bundles, their typical structures, and their functions in discourse in Biology. The findings support the idea that lexical bundles are a basic linguistic construct with important functions for the construction of discourse in this area. Concluding discussion highlights the pedagogical implications of using research journals and/or textbooks to teach English to biologists in a second language context. Furthermore, the importance of explicit instruction in these word combinations in courses on English for Biologists is emphasized.