Which of the following is an example of Mutualism?

The correct answer is Option (4) → Fig tree and wasp

Mutualism is an interaction in which both species benefit (+/+). Lichens (fungus and alga) and mycorrhizae (fungus and plant roots) are examples. Plant-pollinator pairs, such as fig trees and their wasps, are among the most striking cases.

Option (1) Orchid growing as an epiphyte on a mango branch — Incorrect. The orchid gains a place to grow, while the mango tree neither gains nor loses. This is commensalism, not mutualism.

Option (2) Ticks on dogs — Incorrect. Ticks feed on the dog’s blood and harm it. This is parasitism (ticks are ectoparasites).

Option (3) Lice on humans and ticks on dogs — Incorrect. Lice on humans and ticks on dogs both live on the outside of their host and harm it. Both are parasitism.

Option (4) Fig tree and wasp — Correct. The female wasp pollinates the fig while looking for a place to lay eggs. In return, the fig gives the wasp an egg-laying site and some developing seeds as food for its larvae. Both gain, so this is mutualism.

NCERT Extract:
Population Interactions – “… (v) Mutualism: This interaction confers benefits on both the interacting species. … In many species of fig trees, there is a tight one-to-one relationship with the pollinator species of wasp …. It means that a given fig species can be pollinated only by its ‘partner’ wasp species and no other species. The female wasp uses the fruit not only as an oviposition (egg-laying) site but uses the developing seeds within the fruit for nourishing its larvae. The wasp pollinates the fig inflorescence while searching for suitable egg-laying sites. In return for the favour of pollination the fig offers the wasp some of its developing seeds, as food for the developing wasp larvae.”