Investigations in Natural Science is a program in secondary school biology, chemistry, and physics based upon the description of science as a quest for knowledge, not the knowledge itself. This teaching guide is designed for use with the 18 biology investigations found in the student manual. These investigations focus on concepts related to: organisms; classification; populations; producers; food chains; ecosystem; cells; cell transport; circulation; calories; digestion; breathing; responses; locomotion; cell division; reproduction; inheritance; and homeostasis. Each investigation includes activities related to the three learning cycle components, namely, exploration, conceptual invention (the idea), and expansion of the idea. The guide contains: (1) a list of biology concepts fostered in each investigation; (2) detailed instructional strategies for the student investigations, which are reproduced in the teacher's manual in reduced form; and (3) student reading questions and answers (the readings, however, appear only in the student manual). Included in appendices are student materials and teaching guide on microscope skills, sample essay evaluation questions for each investigation, and a list of equipment and materials needed for each investigation. (JN)