Question

Assertion (A): The prickly pear cactus introduced into Australia caused havoc by spreading rapidly into millions of hectares of land.
Reason (R): When certain exotic species are introduced into a geographical area, they tend to become invasive and start spreading fast because of the absence of the natural predators

• A. Both A and R are true and R is the correct explanation of A
• B. Both A and R are true and R is not the correct explanation of A
• C. A is true, but R is false
• D. A is false, but R is true

Answer 1

The correct option is A Both A and R are true and R is the correct explanation of A

Predation is one of the types of population interactions which contributes more to the ecological balance.

Prey refers to the organisms which the predators feed upon.
Predators maintain the prey population under control. In the absence of predators, the prey population increases significantly causing ecosystem instability. This has been noticed in the 1920s in Australia when prickly pear cactus was introduced.

Prickly pear cactus is an exotic species. A species not native to a particular area is called exotic species.

This cactus created havoc by spreading rapidly into millions of hectares of rangeland. The reason for the rapid increase in their number is due to the absence of the natural predators in the new area.

Several methods were employed to bring this invasive cactus under control but it was of no great help. Finally, a cactus feeding moth from its natural habitat was introduced. The cactus feeding predator moth successfully brought the cactus under control. Hence, predators keep the prey population under control.

Therefore, both A and R are true and R is the correct explanation of A.