NDA Biology · Biodiversity and Classification

The Five Kingdoms and Kingdom Fungi

All living things are sorted into five kingdoms (Monera, Protista, Fungi, Plantae, Animalia) by cell type, cellularity and nutrition; Fungi are the eukaryotic, chitin-walled, spore-forming decomposers that cannot photosynthesise.

All Biodiversity and Classification notes NDA Biology strategy

Why this matters

Start here — the five-kingdom system is the frame the whole chapter hangs on, and the NDA tests it directly. Two facts carry the marks: which kingdoms are made of only single cells (Monera and Protista), and the signature features of Fungi (chitin cell wall, mycelium, spores, NO photosynthesis). Both PYQs in this subtopic are EASY — pure recall.

Concept 1 of 2

Whittaker's five-kingdom classification

Intuition

Every organism on Earth belongs to one of five kingdoms. The first split is the cell type: Monera is the only kingdom of prokaryotes (no true nucleus); the other four are all eukaryotes. After that, kingdoms differ by how many cells they have and how they get food.

Definition

R. H. Whittaker (1969) proposed the five-kingdom system, splitting life on cell structure, body organisation and mode of nutrition:

Monera — prokaryotes (no true nucleus); always unicellular. Bacteria, blue-green algae (cyanobacteria).
Protista — eukaryotes; unicellular. Amoeba, Paramecium, Euglena.
Fungi — eukaryotes; mostly multicellular; saprophytic decomposers (absorb food). Mushrooms, moulds, yeast.
Plantae — eukaryotes; multicellular; autotrophs that photosynthesise. All green plants.
Animalia — eukaryotes; multicellular; heterotrophs that ingest food. All animals.

Worked example

Bacteria and Amoeba are both single-celled. Why are they placed in different kingdoms?

A bacterium is a prokaryote — its DNA is not enclosed in a true membrane-bound nucleus → kingdom Monera.
An Amoeba is a eukaryote — it has a true nucleus and membrane-bound organelles, but is still single-celled → kingdom Protista.
The deciding feature is cell type (prokaryote vs eukaryote), not the number of cells.

Answer:Bacteria are prokaryotes (Monera); Amoeba are unicellular eukaryotes (Protista).

Practice this conceptself-check · 4 quick reps

Try it yourself

Place each in its kingdom: (a) a mushroom, (b) cyanobacteria, (c) Paramecium, (d) a mango tree.

Practice — Level 1 (4 reps)

Quick reps to lock in the method. Try each, then check.

1.
Which two kingdoms contain only unicellular organisms?
2.
Which is the only kingdom of prokaryotes?
3.
Which kingdom do Amoeba and Paramecium belong to?
4.
Who proposed the five-kingdom system?

From the bank · past-year question

Example 1Biodiversity and ClassificationEASY

Which of the following kingdoms has/have only unicellular organisms?

[Q60 · Sep · 2018]

Only Monera and Protista are 'only unicellular'

The bank asks which kingdoms have only single-celled members. Monera (always unicellular) and Protista (unicellular eukaryotes) both qualify. Fungi is wrong — it has multicellular members (mushrooms). Watch the distractor 'Protista and Fungi'.

Unicellular is not the same as prokaryote

Both Monera and Protista are unicellular, but only Monera is prokaryotic. Protista cells are eukaryotic (true nucleus). The first split in the five-kingdom system is cell type, not cell count.

Concept 2 of 2

Kingdom Fungi — features

Intuition

Fungi look plant-like (they are fixed, branching, and live in soil) but they are NOT plants. The single most-tested point: fungi cannot photosynthesise — they have no chlorophyll, so they feed by absorbing nutrients from dead matter (saprophytes). Their cell wall is made of chitin (like an insect's shell), not cellulose.

Definition

Defining features of Kingdom Fungi:

No chlorophyll → cannot photosynthesise; they are heterotrophs (saprophytes/parasites that absorb food).
Cell wall of chitin — not cellulose (which is the plant cell wall).
Body is a network of thread-like filaments called hyphae, forming a mycelium.
Reproduce by spores (both asexual and sexual).
Examples: mushrooms, moulds (Rhizopus), yeast (unicellular), Penicillium.

Feature	Fungi	Contrast
Nutrition	Heterotroph — no photosynthesis (no chlorophyll)	Plants are autotrophs NDA 2023 — 'can carry out photosynthesis' is NOT a feature of fungi; it is the odd one out.
Cell wall	Chitin	Plants use cellulose
Body	Mycelium of thread-like hyphae	Not roots/stems/leaves
Reproduction	By spores (asexual + sexual)	Not by seeds
Examples	Mushroom, mould, yeast, Penicillium	Yeast is unicellular

Fungi are decomposers, not producers — the green-plant feature (photosynthesis) is exactly what they lack.

Practice this conceptself-check · 4 quick reps

Try it yourself

A student claims fungi are plants because they grow in soil and don't move. Give two features that prove fungi are NOT plants.

Practice — Level 1 (4 reps)

Quick reps to lock in the method. Try each, then check.

1.
Can fungi carry out photosynthesis?
2.
What is the fungal cell wall made of?
3.
What is the network of fungal filaments called?
4.
How do fungi reproduce asexually?

From the bank · past-year question

Example 2Biodiversity and ClassificationEASY

Which one of the following is not a characteristic feature of fungi?

[Q105 · Apr · 2023]

Photosynthesis is the feature fungi LACK

A 'which is NOT a feature of fungi?' question lists chitin wall, mycelium and spores (all true) alongside 'can carry out photosynthesis' (false). Fungi have no chlorophyll — the photosynthesis option is always the answer to the 'not a feature' version.

Chitin, not cellulose

Fungal cell walls are chitin; plant cell walls are cellulose. Don't let the plant-like appearance of fungi pull you to 'cellulose'.

Summary — formulas & gotchas at a glance

A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.

Reference tables (1)

Kingdom Fungi — features5 rows

Feature	Fungi	Contrast
Nutrition	Heterotroph — no photosynthesis (no chlorophyll)	Plants are autotrophs NDA 2023 — 'can carry out photosynthesis' is NOT a feature of fungi; it is the odd one out.
Cell wall	Chitin	Plants use cellulose
Body	Mycelium of thread-like hyphae	Not roots/stems/leaves
Reproduction	By spores (asexual + sexual)	Not by seeds
Examples	Mushroom, mould, yeast, Penicillium	Yeast is unicellular

Fungi are decomposers, not producers — the green-plant feature (photosynthesis) is exactly what they lack.

Watch out for (4)

Only Monera and Protista are 'only unicellular'
→ Whittaker's five-kingdom classification
Unicellular is not the same as prokaryote
→ Whittaker's five-kingdom classification
Photosynthesis is the feature fungi LACK
→ Kingdom Fungi — features
Chitin, not cellulose
→ Kingdom Fungi — features

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