BYSTRIANSKA,Viktória: Impact of light pollution on the biotic component of the environment. [BACHELOR THESIS]. Technical university in Zvolen. Faculty of Ecology and Environmental science; Department of Applied Ecology. Supervisor: doc. Ing. Jana Škvareninová, PhD., Degree of Professional qualification: Bachelor (Bc.). Zvolen – FEE TU in Zvolen, 2018. 65 s.Invention of artificial light is one of the most important technological advances, though its aggregated and unreasonable introduction has an adverse impact on humans, the ecological and evolutionary aspects of plants, animals and can transform entire ecosystems. In the introduction, thesis work deals with the issue of light pollution and its sources, the legislation dealing with light pollution in Slovakia and in some states of the world and with the concept of phenology and phenological phases. A substantial part of the work brings together findings about the observed adverse effects of light pollution on animals, plants and changes in their natural behaviour. The aim of the work is to investigate the effect of light pollution on trees in the city of Zvolen based on our own observations using phenology. The object of observation was to find out the onset of phenological phases of yellowing and falling of leaves on illuminated and non-illuminated parts of trees. Observations took place between september and november of 2017. The results is graphical representation and verbal evaluation and comparison of detected phenological data.