Lichens, which are capable of initiating ecolological succession even on a bare rock, are actually a symbiotic association of
Contents15
- Aalgae and bacteria
- Balgae and fungi
- Cbacteria and fungi
- Dfungi and mosses
Show answer
Answer: (B) algae and fungi
Lichens = Algae + Fungi living together (symbiosis/mutualism).
The algae (or cyanobacteria) do photosynthesis and make food, while the fungi provide structure, protection, and help retain moisture.
This partnership is so tough that lichens can colonise bare rock — making them pioneer species in ecological succession.
Remember: it's NOT bacteria, NOT mosses.
(NCERT Class 12 Biology, Ch.13)
Lichens are pioneer species that can colonize bare rock and initiate primary succession where no other organisms can survive.
The symbiotic relationship involves algae providing food through photosynthesis while fungi provide structure and moisture retention.
UPSC tests the specific components of this mutualistic association, with common traps being bacteria or mosses instead of the correct algae-fungi partnership.
Lichens: Algae-Fungi Symbiosis
Environment Lichens symbiotic association algae and fungi
Lichens: Structure, Symbiosis & UPSC Key Facts
Lichens are algae + fungi in symbiotic partnership
Algae photosynthesize and make food, fungi provide structure and protection
Pioneer species that can colonize bare rocks
Composite organisms - neither plant nor fungus alone
What Are Lichens
Lichens are composite organisms formed by the symbiotic association of algae and fungi. This partnership is so successful that lichens can survive in extreme conditions where neither partner could live alone.
Symbiotic Partnership
Partner | What It Provides | What It Gets | Key Role |
|---|---|---|---|
Algae (or Cyanobacteria) | Food via photosynthesis | Structure, protection, moisture | Primary producer |
Fungi | Body structure, protection, water retention | Organic food from algae | Support system |
Ecological Significance
Pioneer species - first to colonize bare rock surfaces during primary succession
Can survive extreme conditions: drought, cold, nutrient-poor substrates
Break down rocks through biochemical weathering - release acids that dissolve minerals
Prepare habitat for other species by creating soil and organic matter
Found on rocks, tree bark, soil, and even man-made structures
Question Connection
This question tests the basic composition of lichens. The correct answer is algae and fungi - this symbiotic partnership enables lichens to initiate ecological succession on bare rock, something neither organism could do alone.
Not bacteria: Though some lichens have cyanobacteria (which are bacteria), the primary partnership is algae-fungi
Not mosses: Mosses are separate plants that may grow after lichens in succession
Not algae-bacteria: This combination doesn't form the tough, structured lichen body
Remember: Fungi provide structure, algae provide food - both essential
Ecological Succession & Pioneer Species
Environment ecological succession bare rock initiating
Ecological Succession: Types, Stages & Pioneer Species
Primary succession starts on bare rock/lifeless areas
Lichens are typical pioneer species in primary succession
Secondary succession occurs after disturbance on previously vegetated land
Succession leads to stable climax community
What Is Succession
Ecological succession is the gradual process by which ecosystems change and develop over time. It involves sequential colonization by different species until a stable climax community is reached.
Types of Succession
Type | Starting Point | Pioneer Species | Timeline | Example |
|---|---|---|---|---|
Primary | Bare rock, no soil | Lichens, mosses | Hundreds of years | Volcanic islands, glacial retreat |
Secondary | Disturbed area with soil | Grasses, herbs | Decades to century | Abandoned farmland, forest fire |
Primary Succession Stages
%%{init: {"flowchart": {"wrappingWidth": 460}}}%%
flowchart TD
s1["`**Bare Rock**
Lifeless substrate - volcanic rock, glacial deposits`"]
s2["`**Pioneer Stage**
**Lichens** colonize, begin rock weathering`"]
s3["`**Moss Stage**
Mosses grow on lichen-created soil`"]
s4["`**Grass Stage**
Grasses and small herbs establish`"]
s5["`**Shrub Stage**
Woody shrubs and small trees appear`"]
s6["`**Climax Forest**
Stable community of large trees`"]
s1 --> s2
s2 --> s3
s3 --> s4
s4 --> s5
s5 --> s6Pioneer Species Characteristics
Hardy organisms that can survive harsh, nutrient-poor conditions
Fast colonizers with efficient dispersal mechanisms
Environmental modifiers - change habitat for future species
Examples: lichens (bare rock), grasses (disturbed soil), algae (aquatic)
Eventually replaced by more competitive species in later succession
Primary vs Secondary: Primary = no soil initially, Secondary = soil present
Lichens pioneer primary succession, not secondary succession
Climax community is stable end-stage, not the pioneer stage
Pioneer species are replaced - they don't persist to climax stage
Symbiosis & Mutualism Types
Environment symbiotic association
Symbiosis Types: Mutualism, Commensalism & Parasitism
Mutualism: both species benefit (lichens, mycorrhiza)
Commensalism: one benefits, other unaffected
Parasitism: one benefits, other harmed
Symbiosis = close, long-term biological interaction
Understanding Symbiosis
Symbiosis refers to close, long-term biological interactions between different species. The relationship can benefit both partners, benefit one, or harm one while benefiting the other.
Types of Symbiotic Relationships
Type | Species A | Species B | Key Examples | UPSC Relevance |
|---|---|---|---|---|
Mutualism | Benefits (+) | Benefits (+) | Lichens (algae-fungi), Mycorrhiza | High - many examples |
Commensalism | Benefits (+) | Unaffected (0) | Epiphytes on trees, Remora-shark | Medium |
Parasitism | Benefits (+) | Harmed (-) | Plasmodium-human, Cuscuta-host | High - disease ecology |
Important Mutualism Examples
Lichens: algae provide food, fungi provide structure and protection
Mycorrhiza: fungi help plant roots absorb nutrients, get carbohydrates in return
Nitrogen-fixing bacteria: provide nitrogen to legumes, get shelter and nutrients
Pollination: insects get nectar, plants get reproductive service
Cleaner fish: remove parasites from larger fish, get food in return
Question Application
The lichen question specifically tests mutualism - both algae and fungi benefit from their association. This makes lichens extremely resilient and able to colonize harsh environments like bare rock.
Mutualism vs Commensalism: In mutualism both benefit, in commensalism only one benefits
Obligate vs Facultative: Some relationships are essential (lichens), others optional
Don't confuse examples: Lichens = mutualism, Epiphytes = commensalism
Lichen partners: Always algae + fungi, never bacteria + fungi or other combinations