Question

The prickly pear cactus became unusually abundant after its introduction in Australia because it
A.Had no co evolved herbivores
B.Formed new mycorrhizal association
C.Lost its thorn
D.All of these

Answer 1

Coevolution occurs when two or more species reciprocally affect each other's evolution through the process of natural selection. Opuntia, commonly called prickly pear, is a genus in the cactus family, Cactaceae

Complete answer:
Coevolution occurs when species evolve together.Co evolution is caused by the selection pressure that each of the two species exerts on the other since there has been no co-evolved herbivore with prickly cactus, it became abundant in Australia.

So, the correct answer is option A . Had no co evolved herbivores
Additional information:
Symbiosis is defined as a short or life long intimate association of two different species as a means of obtaining food by one or both the partners but may also provide protection to one member from enemies.The species participating in symbiosis are termed symbionts or symbiotes.Members of different populations often interact i.e. affect each other in various ways in their environment.Their interactions are based on three factors (i) nature of food and mode of obtaining it, (ii) kind of space needed as shelter and (iii) habits such as aggregation, breeding etc.
The interaction between the members of two species are of three main types- Positive or beneficial interactions , negative or antagonistic interaction, and neutral interaction .

Note:
Co evolution usually occurs in species having symbiotic association.
Commensalism, mutualism, amensalism, parasitism , competition , parasitism , predation are some type of interaction between two species.