Invasive species are plants or animals that are not native to a particular ecosystem and have been introduced either intentionally or accidentally by humans. They can have a negative impact on native species and ecosystems, as they often compete for resources such as food and habitat. They can also spread diseases and parasites, and can cause changes in the structure and function of ecosystems.
Additionally, some exotic species may have been introduced intentionally as ornamental plants or pets, while others may have been accidentally introduced through trade or travel.
Overall, the presence of exotic flora and fauna in different parts of the world is usually the result of human activity, either intentionally or unintentionally.