Biology · BIOLOGICAL CLASSIFICATION

Lichens are composite symbiotic associations consisting of an algal component (phycobiont) and a fungal component (mycobiont). Which statement accurately describes their physiological interdependence and ecological significance?

1. Phycobiont provides structural shelter and absorbs minerals; mycobiont performs photosynthesis
2. Phycobiont (autotrophic) synthesizes food for the fungus; mycobiont (heterotrophic) provides shelter and absorbs mineral nutrients and water; lichens do not grow in polluted areas
3. Both components synthesize food independently and function as major indicators of high sulfur dioxide pollution
4. Mycobiont fixes atmospheric nitrogen for the phycobiont; lichens flourish predominantly in industrial cities