What is one of the reasons why exotic species sometimes become invasive and spread rapidly?

Absence of natural predators

The correct answer is Option (1) -Absence of natural predators

Exotic species, also known as introduced, alien, non-indigenous, or non-native species, can become invasive and spread rapidly in new environments. One of the reasons for their successful invasion is the absence or limited presence of their natural predators in the new habitat. Without natural predators to control their population, exotic species can experience unrestricted growth and reproduction.

The absence of natural predators allows exotic species to exploit available resources without facing significant predation pressure. This gives them a competitive advantage over native species, leading to their proliferation and colonization of new habitats. Without the control exerted by natural predators, the invasive species can outcompete native species for food, space, and other resources, leading to their displacement or extinction.

One example of this is the case of the prickly pear cactus, which was introduced into Australia in the early 1920s. Without its natural predators or controls, the prickly pear cactus quickly spread across millions of hectares of rangeland, posing a significant threat to the local ecosystem and agricultural activities.

To address the invasive growth of the prickly pear cactus, a solution was found in the form of a cactus-feeding predator, a moth. This moth, which naturally feeds on the prickly pear cactus in its native habitat, was introduced into Australia as a biological control agent. The introduction of the moth proved to be successful in managing the invasive cactus population.

The moth effectively feeds on the prickly pear cactus, reducing its growth and limiting its spread. This biocontrol method helped restore the natural balance in the ecosystem and brought the invasive cactus under control.

This example illustrates the importance of natural predators and biological control agents in regulating the population growth of invasive species. Introducing the natural predators or agents from the species' native habitat can provide an effective and environmentally friendly approach to managing and controlling invasive species.