This study aims to determine those topics and concepts that biology and science teacher candidates find most challenging to learn in biology lessons. A qualitative case study research method was used to this end. A total of 132 science and biology teacher candidates studying at a state university were asked to write down the ten subjects or concepts they found difficult to learn in biology and the order in which these came to mind. As a result of the content analysis of the collected data, a novel concept map was created using the Processing 3.3.4 software. According to this map, the subjects that teacher candidates found most challenging to learn in biology are circulatory, genetics, respiratory, and energy. Comparably, those subjects they found least challenging to learn were Basic components of living things, Support and movement systems, and Evolution. The results of the novel mind map can help researchers conduct studies on subjects that are difficult to learn in biology. The results of the novel mind map produced by this study will help future research on subjects that are difficult to learn in the field of biology.