The trap you already fall for: a question lists a photosynthetic, unicellular organism and you place it in Protista — or worse, Plantae. The deciding criterion is never photosynthesis or cell count. It is always: does it have a membrane-bound nucleus?
Kingdom Monera comprises all prokaryotes — organisms whose genetic material is not enclosed in a nuclear membrane. This includes bacteria (eubacteria) and archaea (archaebacteria). Key features from NCERT Class 11 Biology Chapter 2, page 13:
The cyanobacteria problem: Blue-green algae (cyanobacteria) photosynthesise using chlorophyll a, which tempts students to classify them under Plantae. They are prokaryotes — Monera. The "algae" in the common name is a historical misnomer. Photosynthesis is irrelevant to kingdom placement; nuclear organisation is the criterion.
NEET relevance: Questions test recall of Monera characteristics and, critically, whether you can distinguish prokaryotic unicellulars (Monera) from eukaryotic unicellulars (Protista). The trap fires on organisms like Nostoc, Anabaena, or Spirulina.
Select an option to see the explanation. Wrong answers show why your choice was tempting — and name the exact trap it exploits.
Which of the following is a characteristic feature of Kingdom Monera?
Answer: C. Monerans are prokaryotes; their genetic material is naked circular DNA (nucleoid) without a nuclear membrane (NCERT Class 11 Biology Chapter 2, page 13).
Why A is wrong: A is wrong because Monera are prokaryotes — they lack a membrane-bound nucleus. Presence of a nuclear membrane defines eukaryotes (Protista, Fungi, Plantae, Animalia).
Why B is wrong: B is wrong because Monera lack all membrane-bound organelles including mitochondria. Aerobic bacteria use mesosomes or plasma membrane for respiration.
Why D is wrong: D is wrong because prokaryotes divide by binary fission. Mitotic spindle formation requires a nucleus with chromosomes — a eukaryotic feature.
Cyanobacteria (blue-green algae) are classified under Kingdom Monera because they:
Answer: B. Classification into Monera is based on prokaryotic cell organisation — absence of a true nucleus. Photosynthesis and unicellularity are irrelevant to this placement (NCERT Class 11 Biology Chapter 2, page 13).
Why A is wrong: A is wrong because photosynthesis is not a criterion for kingdom classification. Cyanobacteria photosynthesise but are prokaryotic, hence Monera — not Plantae. (trap: Monera vs Protista confusion — mode of nutrition does not determine kingdom).
Why C is wrong: C is wrong because unicellularity is shared between Monera and Protista. The distinguishing criterion is prokaryotic vs eukaryotic organisation, not cell number.
Why D is wrong: D is wrong because cyanobacteria have peptidoglycan (not cellulose) in their cell wall. Cellulose cell walls are found in plant cells.
Which organism is correctly placed in Kingdom Monera?
Answer: A. Nostoc is a cyanobacterium — a filamentous, photosynthetic prokaryote classified under Monera (NCERT Class 11 Biology Chapter 2, page 13).
Why B is wrong: B is wrong because Paramoecium is a ciliated eukaryotic protist — Kingdom Protista. (trap: unicellular ≠ Monera; the nuclear membrane is the criterion).
Why C is wrong: C is wrong because Amoeba is a eukaryotic unicellular organism classified under Protista. It has a membrane-bound nucleus.
Why D is wrong: D is wrong because Euglena is a eukaryotic flagellate classified under Protista despite having chloroplasts. Nuclear membrane present.
A student observes a unicellular organism that is photosynthetic but lacks a nuclear membrane. The organism most likely belongs to:
Answer: C. The absence of a nuclear membrane identifies the organism as prokaryotic, placing it in Kingdom Monera regardless of its photosynthetic ability. This matches cyanobacteria (NCERT Class 11 Biology Chapter 2, page 13).
Why A is wrong: A is wrong because Plantae are eukaryotic multicellular organisms. Photosynthesis alone does not qualify an organism for Plantae — nuclear organisation matters first. (trap: Monera vs Protista confusion — photosynthesis tempts placing in Plantae).
Why B is wrong: B is wrong because Protista are eukaryotic. Despite being unicellular and sometimes photosynthetic (like Euglena), they all possess a membrane-bound nucleus. This organism lacks one.
Why D is wrong: D is wrong because fungi are eukaryotic heterotrophs. They never photosynthesise and always have membrane-bound nuclei.
Which of the following statements about bacteria is INCORRECT?
Answer: C. Eubacterial DNA is NOT associated with histone proteins — it is naked. This distinguishes prokaryotic DNA from eukaryotic chromatin. (Note: archaebacteria have histone-like proteins, but the general statement for bacteria refers to eubacteria; NCERT Class 11 Biology Chapter 2, page 13.)
Why A is wrong: A is correct factually (binary fission is the primary mode), so choosing it means you confused 'incorrect statement' with 'correct statement'. Binary fission is indeed the main reproductive mode in bacteria.
Why B is wrong: B is correct factually — bacteria have 70S ribosomes (50S + 30S subunits). Selecting this means confusing bacterial ribosomes (70S) with eukaryotic cytoplasmic ribosomes (80S).
Why D is wrong: D is correct factually — nitrifying bacteria (Nitrosomonas, Nitrobacter) are chemoautotrophic. Selecting this means you forgot that autotrophy in Monera includes both photo- and chemoautotrophy.
Mycoplasma differs from typical bacteria in that it:
Answer: A. Mycoplasma is the smallest known free-living prokaryote and is unique among bacteria in completely lacking a cell wall. It is bounded only by a plasma membrane (NCERT Class 11 Biology Chapter 2, page 13).
Why B is wrong: B is wrong because Mycoplasma is prokaryotic — it belongs to Kingdom Monera and lacks a membrane-bound nucleus like all other monerans.
Why C is wrong: C is wrong because Mycoplasma, being prokaryotic, has 70S ribosomes. 80S ribosomes are characteristic of eukaryotic cytoplasm.
Why D is wrong: D is wrong because Mycoplasma divides by binary fission like other bacteria. Mitosis requires a nucleus with condensed chromosomes — absent in prokaryotes.
Which pair of organisms belongs to Kingdom Monera?
Answer: D. Both Nostoc and Anabaena are filamentous cyanobacteria — prokaryotic photosynthesizers classified under Monera (NCERT Class 11 Biology Chapter 2, page 13).
Why A is wrong: A is wrong because Chlorella is a eukaryotic unicellular green alga (Protista/Plantae). Spirulina is Monera (cyanobacterium), but the pair is mixed.
Why B is wrong: B is wrong because Spirogyra is a filamentous green alga — eukaryotic, classified under Plantae (or Protista in some schemes). Nostoc is Monera, but the pair is mixed. (trap: both are filamentous and photosynthetic, but nuclear organisation differs).
Why C is wrong: C is wrong because Chlamydomonas is a unicellular green alga — eukaryotic (Protista/Plantae). Anabaena is Monera, but the pair is mixed.
An organism is found to have: (i) no nuclear membrane, (ii) photosynthetic pigments, (iii) nitrogen-fixing ability, (iv) filamentous structure. This organism is most likely:
Answer: B. The combination of prokaryotic organisation (no nuclear membrane) + photosynthesis + nitrogen fixation + filamentous habit uniquely identifies Anabaena — a heterocyst-bearing cyanobacterium in Monera. Rhizobium fixes nitrogen but is not photosynthetic or filamentous. Spirogyra is filamentous and photosynthetic but eukaryotic (NCERT Class 11 Biology Chapter 2, page 13).
Why A is wrong: A is wrong because Rhizobium is a nitrogen-fixing bacterium (Monera) but it is neither photosynthetic nor filamentous. It satisfies only criteria (i) and (iii).
Why C is wrong: C is wrong because Spirogyra is filamentous and photosynthetic but is eukaryotic (has a nucleus) and does not fix nitrogen. It fails criteria (i) and (iii). (trap: Monera vs Protista confusion — both are filamentous green organisms).
Why D is wrong: D is wrong because Mucor is a filamentous fungus — eukaryotic, heterotrophic, non-nitrogen-fixing. It satisfies only criterion (iv).
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Pattern: Identification and classification of organisms into kingdoms (PYQ pattern: recall + similar-term-confusion distractors).
Given
An organism has the following characteristics:• Unicellular• Photosynthetic (contains chlorophyll a)• No membrane-bound nucleus• Found in freshwater ponds forming green blooms
Required
Identify the kingdom to which this organism belongs and justify.
Concept
Five-kingdom classification (Whittaker, 1969) separates organisms primarily by cell type (prokaryotic vs eukaryotic), then by cell number, nutrition mode, and body organisation.
Decision criteria (in place of formula)
• Nuclear membrane absent → Prokaryote → Kingdom Monera• Nuclear membrane present → Eukaryote → further classification by nutrition/organisation
Application
The organism lacks a membrane-bound nucleus → prokaryotic.
Despite being photosynthetic and unicellular (features shared with some protists and plants), the absence of nuclear membrane overrides all other features.
Classification
Kingdom Monera. The organism is a cyanobacterium (blue-green alga).
Final answer
Kingdom Monera — because the fundamental criterion for Monera is prokaryotic cell organisation (no nuclear membrane), which this organism satisfies.
Common trap
Students are tempted to place this organism in Plantae (because it photosynthesises) or Protista (because it is unicellular). The trap fires because both photosynthesis and unicellularity are SHARED features across kingdoms. The DECIDING feature is always nuclear organisation: prokaryote → Monera, eukaryote → look further.
Similar NEET-style question
"Spirulina is classified under Kingdom Monera and not Protista because it: (A) is photosynthetic (B) is unicellular (C) lacks membrane-bound organelles (D) has a cell wall."
Answer: C — absence of membrane-bound organelles (including nucleus) = prokaryotic = Monera.
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Monera comprises all prokaryotes — bacteria and archaea. Bacteria classified by shape (cocci, bacilli, spirilla, vibrio) and Gram staining. Archaebacteria thrive in extreme habitats — methanogens, halophiles, thermoacidophiles.
-- NCERT Class 11 Biology, Ch. 2, p. 12These are the exact patterns that cause wrong answers in NEET. Each trap includes when it triggers and how to avoid it.
Category: Similar Terms
Both kingdoms include single-celled organisms but Monera is prokaryotic; Protista eukaryotic.
Question lists organisms and asks for kingdom; tempts placing all unicellulars in same kingdom.
Test for nucleus: prokaryote → Monera; eukaryote → Protista regardless of being unicellular.
Root cause: term confusion
Cyanobacteria (blue-green algae) are prokaryotic — Monera, not Plantae. They photosynthesise but lack nucleus.
More in Diversity in Living World: 14 exam traps and mistakes · 1 question pattern from its other lessons.
4 questions from NEET 2022, 2025, 2026. Answers verified against NTA official keys.
Which of the following is not a prokaryote ?
Which of the following is a correct statement?
All 59 past-paper questions from Diversity in Living World →
Page numbers are the ones printed in the current NCERT textbook (2023 rationalised edition), unless marked pre-2023. The books are free at ncert.nic.in.
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