Keystone Species Role in Biodiversity — NEET Biology

Correct answer: B — S1 and S3

The core concept tested here is the ecological roles of predators and various adaptations related to predation. S1 is correct. The NCERT text states, "Predators also help in maintaining species diversity in a community, by reducing the intensity of competition among competing prey species." The example of the starfish Pisaster is given. S2 is incorrect. "Prudent predators" implies that predators do not overexploit their prey to the point of extinction, as it would lead to their own eventual demise due to lack of food. The NCERT states, "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. This is the reason why predators in nature are ‘prudent’." S3 is correct. The NCERT mentions, "Biological control methods adopted in agricultural pest control are based on the ability of the predator to regulate prey population." S4 is incorrect. In a broad ecological context, herbivores are indeed considered predators because they consume plant parts, thus transferring energy. The NCERT explicitly states, "Although animals eating plants are categorised separately as herbivores, they are, in a broad ecological context, not very different from predators." S5 is incorrect. The Monarch butterfly acquires its chemical during its caterpillar stage, not its adult stage, by feeding on poisonous weeds. The NCERT states, "Interestingly, the butterfly acquires this chemical during its caterpillar stage by feeding on a poisonous weed." Therefore, statements S1 and S3 are correct. The correct option is B because it accurately identifies S1 and S3 as the correct statements.