When it comes to the earliest days of biology at the University of Zagreb, what we are really discussing is the development of botany and zoology, the only professions of the time that represented biology from the 17th to the 19th century. However, neither the Jesuit Neo Academia Zagrabiensis (1669-1773), nor the royal Regia Scientiarum Academia (1773-1850), nor the Orthodox Academy (1859-1874) provided the appropriate conditions for the development of scientific and teaching activities in biology in Zagreb. That is why the first scientific discussions in the field of biology were berthed outside of these institutions, and it was in 1780 that the Jesuit Augustin Michelazzi published the Compendium Regni Vegetabilis (Gorizia, 1780), outlining the insights in botany of the time. That same year, Peter Nutrizio Grisogono published the natural geography atlas of Dalmatia, Notizie per servire alla storia naturale della Dalmazia, in which he gave an overview of the fauna of the Adriatic Sea. Increasingly frequent discussions in natural sciences followed soon after, including botany and zoology, i.e. biology. These scientific discussions, along with others, fostered the idea of a need to establish a university such as those that “advanced” nations had. After lengthy debate, the Croatian Parliament established the University (1874), within which three faculties were established. Among them was the Faculty of Philosophy and its Department of Mathematics and Natural Sciences. This year marked the beginning of organised scientific and teaching work at the University of Zagreb as well as the initiation of the systematic development of biology in our country. Gradually, new departments and divisions were established within the Department of Mathematics and Natural Sciences, including the Department of Zoology and the Division of Botany and Physiology.
Classes in biology began on 21 April 1876, in the summer semester. That year, only botany professor Dr Bohuslav von Jiruš held classes, whereas zoology professor Dr Spiridion Brusina began doing so in April 1877. The natural sciences within the Faculty of Philosophy were never able to procure sufficient resources for contemporary scientific work, and especially not for experimental work, which is why their aspiration to become independent and transform into a separate faculty was understandable. This was realised in 1946, when the Faculty of Science was founded. Looking back at the development of the Department of Biology during this period, it was undoubtedly the centre of many naturalistic research directions in the Republic of Croatia and the wider region. Initially, the research included two basic directions: botany and zoology. Research covered all areas of botany and zoology; from cells and organisms to communities. Groundwater ecology and fauna studies were worthy of particular note. During this period, many members of the Department profiled themselves into leading Croatian botanists and zoologists, whose expertise was also recognised internationally. Here we should mention the botanist Prof Radovan Domac, author of Little Flora of Croatia, Prof Beatrice Đulić, whose collection of small mammals is one of the most valuable and interesting in this part of Europe (now owned by the Department), and Prof Milan Meštrov, a pioneer of biospeleological research.