The 35th IBO brought together about 300 students from 80 countries, and the contest comprised practical exams, which included experiments, and theoretical exams.
Croatia's delegation consisted of four students plus their mentors.
Vrdoljak is a senior student of the "III. Gimnazija" in Split and Markulin is a senior student of the "XV. Gimnazija" in Zagreb.
The International Biology Olympiad (IBO) is the association that organizes the world's premier biology competition for secondary school students.