In this lesson, students learned about the classification of species into alien, indigenous, and endemic groups, focusing on the impact of alien species, also known as invasive species, on local ecosystems. Alien species are defined as plants or animals that are introduced to Malta from other countries, disrupting native flora and fauna. The lesson highlighted examples from around the world, such as the introduction of zebra mussels in the United States and cane toads in Australia, emphasizing the significant ecological and economic threats posed by these species.