In addition to the 90 ECTS major program in Biology, it is possible to choose a 30 ECTS Master's minor degree program (Master's degree 90 ECTS + 30 ECTS -> 120 ECTS Master's degree program). Some Master's minor degree program follow consecutively on a Bachelor's minor degree program, and some can be started during the Master's.
In particular, it is possible to acquire the subject-specific scientific requirements for the teaching diploma "Lehrdiplom für Maturitätsschulen" in a second subject by combining a minor of 60 ECTS in the Bachelor and a 30 ECTS minor in the Master program.
Note that the Master's thesis project in Biology takes one year of full-time study. Any minor degree program must be planned around this. Even if the minor consists of 30 ECTS credits, it is rather impossible that it can be completed within one semester.