What do you understand by 'exotic species'?
Exotic species are species which are not the natural inhabitants of the local habitat but are introduced into the system. These species do not originally belong to the local ecosystem and are brought in from outside.
The introduction of exotic species can cause extensive damage to the natural biotic community of the ecosystem. There are many examples where ecosystems have suffered because of such introductions. For instance, the islands of Hawaii have many unique plants and animals that are threatened by introduced species and land development.
Explanation
The textbook clearly defines exotic species in the first paragraph of the provided context. The definition is straightforward: species not natural to the local habitat but introduced into the system. The context also mentions their negative impact on natural biotic communities and provides Hawaii as an example where unique plants and animals are threatened by introduced species. This answer covers the definition and impact within the required word limit for a 2-mark question.