This story looks at some of Scotland's 'alien' plants and animals.
Plants and animals that do not originally come from Scotland but have arrived here because of people's actions.
Many alien species can live happily with Scotland's native animals and plants. But others can harm and even destory them.
Some alien species were introduced so long ago that they are often thought of as native to Scotland. And many exotic-looking species are actually native.
Try out the Alien or Native? quiz.