Biology and Ecology of Lichens: PTE Listening: Fill in the Blanks practice questions

Lichens are not single organisms but complex composite structures formed by a mutualistic between fungi and photosynthetic partners. The fungal component, known as the mycobiont, provides physical and absorbs moisture from the surrounding atmosphere. In return, the photosynthetic partner, which is usually green algae or cyanobacteria, manufactures vital nutrients through processes. This shared arrangement allows lichens to colonise bare rocks and harsh terrains where neither organism could survive independently. Over centuries, these durable organisms slowly break down mineral and contribute to the formation of early soils.

Because lichens lack roots and protective outer membranes, they absorb all their water and nutrients directly from the air. This physiological characteristic makes them extremely sensitive to chemical such as sulphur dioxide and heavy metals. Ecologists frequently use lichen diversity to monitor atmospheric quality across industrial and urban regions. When air pollution rises, the most delicate lichen varieties gradually from tree bark and stonework, leaving behind only the most species. By mapping these population shifts over time, scientists can detect subtle changes without relying entirely on electronic recording devices.

Following volcanic eruptions or glacial retreats, exposed bedrock presents an exceptionally environment for most vegetation. Lichens are typically the first pioneer colonisers to establish themselves on these barren expanses. By releasing specialised organic acids, they slowly the rocky substrate beneath them. This chemical action, combined with natural weathering from wind and frost, fractures the stone into microscopic over decades. As generations of lichens die and their organic remains blend with the mineral dust. This gradual accumulation creates the initial layer of fertile required for mosses and vascular plants to take root.