Which of the following statements are correct?

(A) A lion eating a deer and a sparrow feeding on grains are ecologically similar consumers.
(B) Predator star fish Pisaster helps in maintaining the species diversity of some invertebrates.
(C) Predators ultimately lead to the extinction of prey species.
(D) Production of chemicals such as nicotine and strychnine by the plants are metabolic disorders.

Choose the correct answer from the options given below.

(A) and (B) only

The correct answer is Option (4) → (A) and (B) only   

Statement (A) is correct. A lion eating a deer is a classic example of predation, where one organism (the predator) kills and consumes another (the prey). Similarly, a sparrow feeding on grains is also a form of predation, specifically herbivory, which is a type of predation where the prey is a plant. In both cases, one organism is consuming another for energy, making them ecologically similar consumers. They are both heterotrophs that obtain energy by feeding on other organisms.

Statement (B) is correct. Predators  help in maintaining species diversity in a community, by reducing the intensity of competition among competing prey species. In the rocky intertidal communities of the American Pacific Coast the starfish Pisaster is an important predator. In a field experiment, when all the starfish were removed from an enclosed intertidal area, more than 10 species of invertebrates became extinct within a year, because of inter- specific competition.

Statement (C) is incorrect. While predators can significantly impact prey populations, they typically do not lead to the extinction of their prey. The relationship between a predator and its prey is a dynamic one, often regulated by co-evolution. As prey populations decline, it becomes harder for predators to find food, leading to a decrease in the predator population. This, in turn, allows the prey population to recover. This cyclical pattern helps maintain a balance rather than leading to extinction.

Statement (D) is incorrect. Chemicals such as nicotine, strychnine, and caffeine produced by plants are not metabolic disorders. Instead, they are secondary metabolites. These compounds are not directly involved in the plant's growth, development, or reproduction. Their primary ecological function is to serve as defensive mechanisms against herbivores and pathogens. They can also attract pollinators or disperse seeds.