Which of the following do not grow in polluted area ?

Correct — option (3), Lichen.

NCERT's Class XI Biology textbook, in its chapter Biological Classification, states: "Lichens are very good pollution indicators – they do not grow in polluted areas."

A lichen is a symbiotic association between an alga and a fungus. The algal partner, the phycobiont, prepares food; the fungal partner, the mycobiont, provides shelter and absorbs mineral nutrients and water.

Because lichens do not grow in polluted areas, finding them missing from a place can point to pollution there. That is what makes them indicators.

So the organism in the options that does not grow in polluted areas is Lichen.

The idea to remember: lichens, the alga–fungus partnership, are pollution indicators because they do not grow in polluted areas.

Why the others are wrong

• (1)
  Pseudomonas — Pseudomonas is a genus of bacteria; NCERT's statement about not growing in polluted areas is made for lichens. A Pseudomonas strain figures instead in a landmark case about oil clean-up. In Diamond v. Chakrabarty (1980), the US Supreme Court held that a human-made micro-organism is patentable subject matter.

  That micro-organism was a genetically engineered Pseudomonas bacterium able to break down multiple components of crude oil, which the Court said was believed to have significant value for treating oil spills.

• (2)
  Algae — Algae is a large group, and many algae grow in polluted water. The Bureau of Indian Standards' IS 10500:2012, Annex C, lists algal species with "Polluted waters" as their habitat.

  Its examples include green algae such as species of Chlorella and Spirogyra, listed for polluted waters and impounded sources, where they clog filters. The same annex lists other algae of clean waters as indicators of purification, so the group as a whole is not confined to clean areas.

• (4)
  Gymnosperms — Gymnosperms are a plant group defined by their seeds, not by where they can grow. NCERT's Class XI chapter Plant Kingdom describes them as plants in which the ovules are not enclosed by any ovary wall, so the seeds are naked.

  They include medium-sized and tall trees and shrubs, such as the giant redwood Sequoia. NCERT's statement about not growing in polluted areas is made for lichens.

A lichen looks like a single organism but is two living together. NCERT describes lichens as symbiotic, mutually useful associations between algae and fungi; the algal component (phycobiont) is autotrophic and the fungal component (mycobiont) is heterotrophic.

Some organisms act as biological indicators of their surroundings. A sensitive organism can point to pollution by being absent, as lichens are from polluted areas. Others thrive in polluted places: IS 10500 lists green algae such as Chlorella and Spirogyra for polluted waters.

Names can mislead here. NCERT notes that cyanobacteria, also called blue green algae, are not counted as algae any more, since members of Monera have been excluded from Plantae.

Key facts

• NCERT Class XI Biology: lichens are very good pollution indicators; they do not grow in polluted areas.
• A lichen is a symbiotic association of an alga (phycobiont, autotrophic) and a fungus (mycobiont, heterotrophic).
• In a lichen, algae prepare food for the fungi; the fungi provide shelter and absorb mineral nutrients and water.
• IS 10500:2012 Annex C lists green algae such as Chlorella and Spirogyra with polluted waters as habitat, where they clog filters.
• Gymnosperms (gymnos: naked, sperma: seeds) have ovules not enclosed by an ovary wall; their seeds are naked.

Common traps

• Mycorrhiza and lichen are both fungal partnerships, but with different partners: lichen is fungus with algae, mycorrhiza is fungus with the roots of higher plants.
• Pollution can show up as absence or as abundance. Lichens do not grow in polluted areas, while IS 10500 lists algae, such as Chlorella and Spirogyra, whose habitat is polluted waters.
• Gymnosperms are named for a structure, their naked seeds, not for any habitat. Do not read a classification name as a statement about pollution.

UnlockIAS will link similar questions from RAS Pre 2013 here once that paper is published on this site.

• practice — not a real PYQ

  In a lichen, the algal component and the fungal component are respectively known as:

  • (a)Mycobiont and phycobiont
  • (b)Phycobiont and mycobiont
  • (c)Phycobiont and mycorrhiza
  • (d)Mycorrhiza and mycobiont
  Answer(2) — NCERT names the algal component the phycobiont and the fungal component the mycobiont. Option (1) reverses them, and options (3) and (4) bring in mycorrhiza, which NCERT describes as an association of fungi with the roots of higher plants, not a lichen partner.
• practice — not a real PYQ

  Which of the following is a symbiotic association between algae and fungi?

  • (a)Mycorrhiza
  • (b)Lichen
  • (c)Viroid
  • (d)Prion
  Answer(2) — NCERT describes lichens as mutually useful associations between algae and fungi. Mycorrhiza is fungi with the roots of higher plants, a viroid is a free RNA without a protein coat, and a prion is an agent of abnormally folded protein, so options (1), (3) and (4) are wrong.