What is mutualism? Explain it with the examples of lichens, mycorrhizae, fig and wasp, and the orchid Ophrys.

1. 1 · Define in one line. Mutualism is a (+, +) interaction in which both species benefit.
2. 2 · Explain lichens and mycorrhizae.
   • Lichen: the fungus gives shelter and water; the alga or cyanobacterium makes food.
   • Mycorrhiza: the fungus helps roots absorb nutrients; the plant gives carbohydrates.
3. 3 · Explain plant-animal mutualism. Plants pay pollinators with pollen and nectar and seed dispersers with fruits, and guard against cheaters.
4. 4 · Describe fig and wasp. A one-to-one partnership: the wasp pollinates while laying eggs; the fig feeds the larvae with some developing seeds.
5. 5 · Describe Ophrys. Sexual deceit: a petal mimics a female bee; the male bee pseudocopulates and transfers pollen; co-evolution keeps the likeness.
6. 6 · Link to real life. Pulses with Rhizobium nodules add nitrogen to Indian farm soils.
7. 7 · Close in one line. So in mutualism the partners' evolution is tightly linked.

Scoring tip: Show the benefit to each partner separately. Writing only 'both benefit' without saying how loses marks.