Biology · Biological Classification · NEET
Lichens are very sensitive to polluted air, especially sulphur dioxide gas from factories and vehicles. They absorb everything from the air and have no protective layer to block toxins. So in polluted areas they simply cannot survive. Because of this, if you see healthy lichens growing on trees or rocks, it tells you the air there is clean. This is why NCERT says they are 'very good pollution indicators.' NEET tests this exact line often.
No. Lichens do NOT grow in polluted areas. This is a very common trick in NEET. Many students think that because lichens 'indicate' pollution, they must live in dirty air. That is wrong. They indicate pollution by being ABSENT. Their absence tells you the air is dirty; their presence tells you the air is clean.
A pioneer species is the very first organism to colonise (start living in) a bare, empty area where nothing grew before, like fresh bare rock. Lichens are the classic pioneers on bare rocks. They release weak acids that slowly break down the rock. Over a long time this creates a thin layer of soil, and then mosses and small plants can grow. So lichens prepare the ground for other life.
Lichens are the pioneers on bare rocks (this is a real NEET 2016 answer). Mosses, liverworts, and green algae need some soil or moisture first, so they come later. Lichens can survive on completely dry bare rock because the fungus part holds water and the algal part makes food. Remember: bare rock, first colonizer = lichen.
These are two separate abilities. As a pioneer species, a lichen is the first to grow on empty bare rock and starts making soil. As a pollution indicator, its presence or absence tells us about air quality. Both come from the same feature: lichens are tough, self-feeding (fungus + alga), but very sensitive to bad air. NEET can ask either one, so learn both.
Lichens have no waxy cuticle or protective covering. They absorb water, minerals, and gases directly from the air over their whole surface. In clean air this is fine. But in polluted air they also absorb toxic gases like sulphur dioxide, which damages the algal partner's chlorophyll. Without the alga making food, the whole lichen dies.
Which of the following statements is correct?
Which of the following would appear as the pioneer organisms on bare rocks?
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Yes. NCERT clearly states lichens are very good pollution indicators. They do this by NOT growing in polluted areas, so their absence warns us that the air is dirty.
Sulphur dioxide (SO2) is the main air pollutant that harms lichens. It damages the algal partner and its chlorophyll, so the lichen cannot survive in industrial or heavily polluted areas.
Because they are the first organisms that can grow on bare, dry rock. They release acids that weather the rock and slowly build a thin soil layer, allowing mosses and plants to grow later. This starts ecological succession.
No. A lichen is a symbiotic (mutually useful) association of two organisms: a fungus (mycobiont) and an alga or cyanobacterium (phycobiont). The alga makes food; the fungus gives shelter, water and minerals.
Lichens come first. Mosses need some soil and moisture, which lichens create over time. So lichens are the pioneers, and mosses appear at a later stage of succession.
