Some species of plants are insectivorous. Why?

Option 2 is correct. Carnivorous (insectivorous) plants possess specialised trapping and digestive structures to capture and digest insects, allowing them to absorb nutrients from prey rather than ‘‘eat’’ in an animal sense [1]. This habit is an adaptation to nutrient‑poor habitats (e.g., bogs, fens, acidic soils) where available nitrogen and other ions in the soil are scarce; by digesting insects they obtain nitrogen, phosphorus and other essential nutrients needed for growth and enzyme/protein synthesis [2]. Nitrogen is particularly important for building proteins and other compounds in plants, explaining why carnivory supplements rather than replaces photosynthesis (they remain autotrophic for carbon and energy) [2].

Sources

1. [1] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 13: Plant Diversity of India > 13.3. INSECTIVOROUS PLANTS > p. 198
2. [2] https://www.researchgate.net/publication/6598494_Nutrient_Limitation_and_Stoichiometry_of_Carnivorous_Plants
3. [3] Science , class X (NCERT 2025 ed.) > Chapter 5: Life Processes > Activity 5.2 > p. 83