When two protozoans, Didinium and Paramecium, were grown together in a petri dish, Didinium engulfed all the Paramecia within a day and then died of starvation. In this case, Didinium must be considered as a

Didinium is the predator and Paramecium is the prey. In general, predators are prudent and do not overexploit their preys because if a predator is too efficient and overexploits its prey, then the prey might become extinct and following it, the predator will also become extinct for lack of food. In the given situation, the predator engulfed all the prey organisms and then died of starvation. So, this predator is not prudent.