Symbiosis basics: Lichens are composite organisms formed by the association of which two partners?

Introduction / Context:
Lichens exemplify symbiosis, combining photosynthetic partners with fungal hosts to occupy habitats ranging from tree bark to bare rock. Understanding their composition is a basic competency in botany and ecology.

Given Data / Assumptions:

• Lichens consist of a mycobiont (fungus) and a photobiont (alga or cyanobacterium).
• The association enables photosynthesis plus structural and moisture retention benefits.

Concept / Approach:
The photobiont provides fixed carbon through photosynthesis; the fungus supplies structure, protection, and microhabitat stability. This division of labor allows lichens to colonize extreme environments where neither partner would thrive alone.

Step-by-Step Solution:

Verification / Alternative check:
Standard taxonomy of lichens documents algal or cyanobacterial photobionts embedded in fungal tissues.

Why Other Options Are Wrong:

• Virus and bacteria: not the lichen partnership.
• Algae and bacteria: missing the fungal component.
• Fungi and mosses: mosses are plants, not the photobiont partner in lichens.
• Archaea and fungi: not the canonical lichen symbiosis.

Common Pitfalls:
Assuming all green surface growths are plant based; lichens are distinct from bryophyte mats.

Final Answer:
Algae (or cyanobacteria) and fungi