"Biology" is not one science -- it is dozens of different sciences, each with its own set of tools and techniques, theories and questions, puzzles and paradigms. Here are some examples of biological sciences:
Biochemistry: biological molecules and their interactions; metabolism
Microbiology: bacteria, viruses, and other microscopic organisms, and their interactions with other organisms
Cytology and Histology: cell structures and their functions
Physiology: functions of tissues, organs and organ systems, such as the muscular system, the nervous system, etc.
