Q22 (IAS/2014) Environment & Ecology › Ecology & Ecosystem Basics › Ecological succession Official Key

Lichens, which are capable of initiating ecological succession even on a bare rock, are actually a symbiotic association of

Result

Your answer: — · Correct: B

Explanation

A lichen is not a single organism; it is a stable symbiotic association between a fungus and algae and/or cyanobacteria.[1] Lichens are commonly recognized as a symbiotic association of a fungus and a chlorophyll containing partner, either green algae or cyanobacteria[2], though it's important to note that cyanobacteria are sometimes present instead of or alongside algae. Lichens are actually two organisms, a fungi and algae. The two organisms occur together and form a symbiotic, or mutually beneficial, relationship.[3]

Among the given options, option B (algae and fungi) is the most accurate answer. Options A, C, and D are incorrect because lichens are not associations of algae and bacteria, bacteria and fungi, or fungi and mosses. The fungal partner provides structure and protection, while the algal or cyanobacterial partner performs photosynthesis to produce nutrients. This unique partnership enables lichens to colonize bare rocks and initiate ecological succession in harsh environments where other organisms cannot survive.

Sources

[1] https://britishlichensociety.org.uk/learning/what-is-a-lichen
[2] https://pmc.ncbi.nlm.nih.gov/articles/PMC4757690/
[3] https://www.canr.msu.edu/news/what_are_lichens_and_what_are_they_doing_on_my_tree

How others answered

Each bar shows the % of students who chose that option. Green bar = correct answer, blue outline = your choice.

Community Performance

Out of everyone who attempted this question.

75%

got it right

Web / Current Affairs

Online pages / news items supporting the statement

Web source

Presence: 5/5

"consist of a symbiotic association of algae (usually green) or cyanobacteria and fungi"

Why this source?

Directly describes the components of a lichen as algae or cyanobacteria together with fungi, showing fungus is a necessary partner.
Refutes the statement as phrased because it emphasizes fungus + (algae or cyanobacteria), not algae + bacteria alone.

Web source

Presence: 5/5

"a stable symbiotic association between a fungus and algae and/or cyanobacteria"

Why this source?

States a lichen is a stable symbiotic association between a fungus and algae and/or cyanobacteria, making the fungal partner explicit.
Shows that saying 'algae and bacteria' alone omits the fungal partner and so is incomplete/misleading.

Web source

Presence: 5/5

"Lichens are commonly recognized as a symbiotic association of a fungus and a chlorophyll containing partner, either green algae or cyanobacteria"

Why this source?

Summarizes lichens as a symbiosis of a fungus and a chlorophyll-containing partner (green algae or cyanobacteria).
Confirms cyanobacteria (bacteria) can be a photobiont, but the fungal partner is still required—so 'algae and bacteria' alone is not the full answer.

Indirect textbook clues (5)

How books hint at the answer

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 9: Indian Biodiversity Diverse Landscape > 4. Lichens > p. 157

Strength: 5/5

“A lichen is a peculiar combination of an alga and a fungus*the two live deriving mutual benefit. They are a group of greyish green plants which grow on rocks, tree-trunks, dead wood, etc. The algae manufactures food which becomes available to the fungus, and the absorbs and retains water and thus keeps the algal cells moist. An example of symbiosis. They are most common in wetlands, rare in rivers and streams and are not found in ground water.”

Why relevant

Explicit definition: 'A lichen is a peculiar combination of an alga and a fungus' — directly states the usual partners in lichens.

How to extend

A student could note that fungus, not bacteria, is named here and so seek external sources/maps of organism groups to check whether bacteria commonly replace fungi in lichens.

Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 1: BASIC CONCEPTS OF ENVIRONMENT AND ECOLOGY > Niche > p. 12

Strength: 5/5

“Some species have symbiotic relationships, an arrangement that mutually benefts and sustains each organism. For example, lichen (pronounced "liken") is made up of algae and fungi living together. Te algae is the producer and food source, and the fungus provides structure and physical support. Teir mutually benefcial relationship (mutualism) allows the two to occupy a niche in which neither could survive alone. An ecological niche consists of: • (i) Habitat– where the species live.• (ii) Food niche what a species eats and decomposes and what species it competes with.• (iii) Reproductive niche how and when it reproduces.• (iv) Physical and chemical niche temperature, moisture, and landform.• (v) Geo-ecological niche– topography, terrain, slope, and soils etc.”

Why relevant

Gives a general rule/example of symbiosis: 'lichen ... is made up of algae and fungi living together' and explains the functional roles (alga = producer, fungus = support).

How to extend

Use this functional-role pattern to ask whether bacteria can perform the same structural/support role or the algal producer role in lichens, then check microbial physiology references.

Science-Class VII . NCERT(Revised ed 2025) > Chapter 2: Exploring Substances: Acidic, Basic, and Neutral > HOLISTIC LENS > p. 10

Strength: 5/5

“Lichens are formed by the association of two living organisms, a fungus and an alga. They grow on rocks and trees in regions that have abundant rainfall and clean air. Do you fi nd lichens on trees in your neighbourhood? Lichens Now, let us classify the substances sorted in Group A, Group B, and Group C in Table 2.2. • The substances in Group A, such as lemon juice, amla juice, tamarind water, and vinegar turned the blue litmus paper to red, implying that these substances are acidic in nature.• The substances in Group B, such as soap solution, baking soda solution, lime water, and washing powder solution turned the red litmus paper to blue.”

Why relevant

Another independent source (NCERT) states 'Lichens are formed by the association of two living organisms, a fungus and an alga', reinforcing the fungus–alga pattern across texts.

How to extend

A student could treat repeated mention of fungus+alga as a strong pattern and look up exceptions (if any) in external taxonomic literature or field guides.

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 9: Indian Biodiversity Diverse Landscape > 1. Algae > p. 156

Strength: 4/5

“The green, non-differentiated plants (non-differentated into organs like root, stem and leaf) possessing chlorophyll are known as Algae. They usually grow in water or in moist situations. The fresh-water algae are generally green or blue-green in colour, whereas the marine ones are red or brown. These are autotrophic plants, as they can manufacture their own food.”

Why relevant

Defines algae as autotrophic producers that grow in moist situations — fits the cited role of algae in lichen as the food-manufacturing partner.

How to extend

Combine this with the fungus–alga pattern to reason that the typical lichen partner needs photosynthetic capability (alga), which bacteria (except cyanobacteria) generally lack; then check whether cyanobacteria are ever lichen partners.

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 4: Aquatic Ecosystem > 4.9. CORAL REEFS > p. 50

Strength: 3/5

“50 • Coral is actually a living animal. Coral has a symbiotic relationship (each gives something to the other and gets something back in return) with 'zooxanthellae' microscopic algae which live on coral [i.e. instead of living on the sea floor, the algae lives up on the coral which is closer to the ocean surface and so that the algae gets adequate light]. • Zooxanthellae assist the coral in nutrient production through its photosynthetic activities. These activities provide the coral with fixed carbon compounds for energy, enhance calcification , and mediate elemental nutrient flux. • The tissues of corals themselves are actually not the beautiful colors of the coral reef, but are instead clear (white)”

Why relevant

Gives an example of symbiosis between a non-fungal partner and algae (coral–zooxanthellae), showing symbiosis can involve algae with various hosts, not specifically bacteria.

How to extend

Use this example to broaden inquiry: since algae commonly form symbioses with fungi and animals, a student could survey whether bacteria also commonly serve as algal partners in lichen-like associations.

Which one of the following is a useful functional association between fungi and the roots of higher plants ?

Transition zone of varied natural vegetation occupying the boundary between two adjacent and differing plant communities is known as

In the grasslands, trees do not replace the grasses as a part of an ecological succession because of

Which of the following have species that can establish symbiotic relationship with other organisms? 1. Cnidarians 2. Fungi 3. Protozoa Select the correct answer using the code given below:

Question map

Lichens, which are capable of initiating ecological succession even on a bare rock, are actually a symbiotic association of

Explanation

PROVENANCE & STUDY PATTERN

SIMILAR QUESTIONS

Which one of the following is a useful functional association between fungi and the roots of higher plants ?

Transition zone of varied natural vegetation occupying the boundary between two adjacent and differing plant communities is known as

In the grasslands, trees do not replace the grasses as a part of an ecological succession because of

Which of the following have species that can establish symbiotic relationship with other organisms? 1. Cnidarians 2. Fungi 3. Protozoa Select the correct answer using the code given below:

The ecological niche of an organism relates to