Organisms and Populations — BIOLOGY STD 12 Science — Question

→ Plants have evolved an astonishing variety of morphological and chemical defences against herbivores.
→ Thorns (Acacia, Cactus) are the most common morphological means of defence.
→ Many plants produce and store chemicals that make the herbivore sick when they are eaten, inhibit feeding or digestion, disrupt its reproduction or even kill it.
→ The weed Calotropis growing in abandoned fields.
→ The plant produces highly poisonous cardiac glycosides and that is why you never see any cattle or goats browsing on this plant.
→ A wide variety of chemical substances that we extract from plants on a commercial scale (nicotine, caffeine, quinine, strychnine, opium, etc.,) are produced by them actually as defences against grazers and browsers.