Question

When alien species are introduced, some of them turn invasive and cause decline or extinction of indigenous species. When a species becomes extinct, the plant and animal species associated with it in an obligatory way also become extinct. Which of the following is most appropriate?

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
• B. Both (A) and (R) are correct but (R) is not the correct explanation of (A)
• C. (A) is correct but (R) is not correct
• D. (A) is not correct but (R) is correct

Hint:

Co-extinction (R) is a consequence of extinction, not the mechanism by which invasive species cause indigenous species to decline (A).

Answer 1

The Correct Option is B

Step 1: Concept
Invasive species ecology and extinction cascades.

Step 2: Meaning
Invasive species outcompete natives causing their extinction; extinction cascades occur when obligate mutualists/parasites also go extinct.

Step 3: Analysis
Statement (A) is correct: introduced invasive species do cause decline/extinction of indigenous species.
Statement (R) is also correct: co-extinctions do occur when obligate associates lose their host.
However, (R) describes a consequence of extinction, not the reason why invasive species cause extinction. Hence (R) is not the explanation of (A).

Step 4: Conclusion
Both (A) and (R) are correct but (R) does not explain (A). Final Answer: (B)