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, either unintentionally or deliberately.
When such species are introduced, some of them turn invasive and cause extensive damage to the natural biotic community of the ecosystem. They can lead to the decline or even extinction of indigenous species.
Examples include the Nile perch introduced into Lake Victoria which led to the extinction of more than 200 species of cichlid fish. Other examples of invasive exotic species include carrot grass (Parthenium), Lantana, water hyacinth (Eicchornia), and the African catfish which threatens indigenous catfishes in our rivers.
Explanation
The textbook defines exotic species as species not naturally found in a local habitat but introduced into the system. The context also links exotic species to 'alien species invasions' - when introduced (intentionally or unintentionally), some become invasive and cause extinction of indigenous species. The answer includes specific examples from the text: Nile perch in Lake Victoria, and invasive weeds like Parthenium, Lantana, water hyacinth, and African catfish. This definition-plus-examples format is ideal for a 2-mark short answer question.
Solution Steps
Step 1: Define exotic species using the textbook definition
Step 2: Explain their impact on native ecosystems and biodiversity
Step 3: Provide relevant examples from the given context to support the answer