Question

Some insects are called phytophagous because:

• A. they avoid feeding on plants due to the presence of thorns and spines
• B. they feed on the plant sap
• C. they avoid feeding on plants due to chemicals produced by the plants
• D. they absorb nourishment from the dead and decaying plant and animal matter

Answer 1

The correct option is B they feed on the plant sap

Predation is a type of interspecific interaction in which the predator eats another organism called prey.

The predators of plants are herbivores. It has been observed that approximately 25 percent of the insects are phytophagous as they feed on the plant sap and other plant parts. Sap refers to the watery fluid that flows through the xylem and phloem of plants.

If over-exploited by predators, the prey species might go extinct and hence it has been observed that the prey species have developed certain defence mechanisms to reduce the impact of predation.

Some plants produce thorns and spines to protect themselves from the predators. Many plants produce chemicals which make herbivores sick when they feed on the plants. These include alkaloids such as caffeine, nicotine and quinine which act as defence against herbivores. Calotropis produces very toxic cardiac glycosides that affect the heart. Hence, this plant is avoided by grazing cattle and goats.

Organisms obtaining nourishment from the dead and decaying plant and animal matter are called saprophagous organisms. Organisms belonging to the kingdom Fungi are good examples.