36 free MCQs on Biological Classification with worked answers and explanations. Whittaker's five kingdom system covering Monera, Protista, Fungi, plus viruses, viroids, and lichens. A foundational NEET chapter on how living organisms are grouped.
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Whittaker's five-kingdom system (1969) groups all cellular life by cell structure and nutrition; viruses, viroids, and lichens fall outside this system entirely since they aren't independently classifiable as one of the five.
Q1.
Who proposed the five kingdom classification system?
Answer: B. R.H. Whittaker
Why: R.H. Whittaker proposed the five kingdom classification in 1969, dividing living organisms into Monera, Protista, Fungi, Plantae, and Animalia.
Q2.
Which of these kingdoms includes all prokaryotic organisms?
Answer: C. Monera
Why: Kingdom Monera includes all prokaryotes, namely bacteria, cyanobacteria, mycoplasma, and archaebacteria.
Q3.
What is the cell wall of fungi made of?
Answer: B. Chitin
Why: Fungal cell walls are made of chitin and other polysaccharides, unlike plant cell walls which are made of cellulose.
Q4.
The network of fungal filaments is collectively called the
Answer: B. Mycelium
Why: Individual filaments are called hyphae; the entire network of hyphae forming the fungal body is called the mycelium.
Q5.
Lichens are a symbiotic association between
Answer: B. Algae and fungi
Why: A lichen is a mutualistic association between an alga (phycobiont, autotrophic) and a fungus (mycobiont, heterotrophic).
Q6.
Which organism causes malaria and belongs to Protista?
Answer: B. Plasmodium
Why: Plasmodium is a sporozoan protist that causes malaria. Trypanosoma causes sleeping sickness and Entamoeba causes amoebic dysentery.
Q7.
Which of the following is a viroid disease?
Answer: B. Potato spindle tuber disease
Why: Potato spindle tuber disease is caused by a viroid, discovered by T.O. Diener in 1971. Viroids lack the protein coat found in viruses.
Q8.
Viruses contain genetic material in the form of
Answer: C. Either DNA or RNA, never both
Why: Viruses contain either DNA or RNA as genetic material, never both together, enclosed in a protein coat called the capsid.
Q9.
Mushrooms belong to which class of fungi?
Answer: C. Basidiomycetes
Why: Mushrooms, bracket fungi, and puffballs belong to class Basidiomycetes. They produce basidiospores on a structure called the basidium.
Q10.
Which structure in cyanobacteria helps in nitrogen fixation?
Answer: B. Heterocyst
Why: Heterocysts are specialized cells in certain filamentous cyanobacteria (e.g., Nostoc, Anabaena) that are the sites of nitrogen fixation.
Q11.
Yeast (Saccharomyces) belongs to which fungal class?
Answer: B. Ascomycetes
Why: Saccharomyces (yeast) is a unicellular member of class Ascomycetes, the sac fungi that produce ascospores within an ascus.
Q12.
Bacteria that thrive in extremely hot and acidic environments are called
Answer: C. Thermoacidophiles
Why: Thermoacidophiles are archaebacteria found in hot, acidic environments such as hot springs. Halophiles live in highly saline habitats.
Q13.
Which of the following organisms is responsible for producing biogas, and survives in marshy areas and the gut of ruminants?
Answer: A. Methanogens
Why: Methanogens are archaebacteria found in the gut of ruminant animals (cattle, buffaloes) and marshy areas; they produce methane, a major component of biogas.
Q14.
Diatoms belong to which group of Protista?
Answer: B. Chrysophytes
Why: Diatoms and golden algae (desmids) are grouped under chrysophytes, found in fresh water and marine environments with cell walls forming a frustule.
Q15.
The protein coat that covers the genetic material of a virus is called the
Answer: B. Capsid
Why: The capsid is the protein coat that encloses the viral genetic material (DNA or RNA). It is made up of small subunits called capsomeres.
Q16.
Which of the following correctly distinguishes archaebacteria from eubacteria?
Answer: B. Archaebacteria have a distinct cell wall structure allowing survival in extreme habitats, eubacteria do not
Why: Archaebacteria differ from other bacteria in having a distinct cell wall structure, which is responsible for their survival in extreme conditions like high salt (halophiles), hot springs (thermoacidophiles), and marshy areas (methanogens).
Q17.
Slime moulds are classified under Protista mainly because
Answer: B. They form an aggregation called plasmodium and are saprophytic
Why: Slime moulds are saprophytic protists that engulf decaying organic matter. Under favorable conditions, they aggregate to form a structure called the plasmodium, which can grow and spread several feet.
Q18.
Dinoflagellates are characterized by which of the following features?
Answer: A. Two flagella, one lateral and one longitudinal, with stiff cellulose plates on the cell wall
Why: Dinoflagellates are mostly marine and photosynthetic, bearing two flagella (one lateral, one longitudinal) and a cell wall with stiff cellulose plates. Some, like Gonyaulax, cause red tides.
Q19.
Which class of fungi is also called the imperfect fungi because their sexual stage is unknown?
Answer: D. Deuteromycetes
Why: Deuteromycetes (imperfect fungi) are so named because only their asexual or vegetative phases are known. Once a sexual stage is discovered, the species is reclassified into its proper class.
Q20.
In the fungal sexual cycle, the correct sequence of events is
Answer: B. Plasmogamy, karyogamy, meiosis
Why: The fungal sexual cycle proceeds as: plasmogamy (fusion of protoplasms of two motile/non-motile gametes), followed by karyogamy (fusion of two nuclei), and then meiosis in the zygote (diploid structure).
Q21.
Rhizopus (bread mould) belongs to which class of fungi and shows what type of mycelium?
Answer: B. Phycomycetes, coenocytic mycelium
Why: Rhizopus belongs to class Phycomycetes, which is characterized by coenocytic (aseptate) mycelium, meaning the hyphae lack septa (cross walls) between cells.
Q22.
Which statement about mycoplasma is correct?
Answer: B. They are the smallest living cells and lack a cell wall
Why: Mycoplasma (PPLO, pleuropneumonia-like organisms) are the smallest known living cells, lacking a cell wall, and can survive without oxygen. They belong to kingdom Monera.
Q23.
Why are viruses not included in any of the five kingdoms?
Answer: B. Because they show no signs of life outside a living host cell and are non-cellular
Why: Viruses are non-cellular, obligate intracellular parasites. Outside a host cell, they are inert and show no characteristics of life, so Whittaker's five kingdom system, based on cellular organisms, excludes them.
Q24.
Who demonstrated that viruses could be crystallized and consist largely of protein?
Answer: C. W.M. Stanley
Why: W.M. Stanley (1935) showed that viruses could be crystallized, and crystals consist largely of proteins. D.J. Ivanowsky first reported viruses, and Beijerinck described the contagious nature of the virus.
Q25.
What is the main difference between a virus and a viroid?
Answer: B. Viroids lack the protein coat present in viruses and have smaller RNA
Why: Viroids consist of free RNA with no protein coat, and the RNA is of much lower molecular weight than that of viruses. Viruses, in contrast, have their nucleic acid enclosed in a protein capsid.
Q26.
Plant viruses are typically composed of which type of nucleic acid?
Answer: A. Single-stranded RNA
Why: Most viruses infecting plants have single-stranded RNA as genetic material. Animal viruses may have single or double-stranded RNA, or double-stranded DNA.
Q27.
A student observes an organism with a peptidoglycan cell wall, no membrane-bound nucleus, and the ability to fix nitrogen using heterocysts. This organism most likely belongs to which group?
Answer: B. Cyanobacteria (Eubacteria)
Why: Cyanobacteria (blue-green algae), classified under eubacteria within Monera, are photosynthetic prokaryotes with chlorophyll a and a rigid cell wall; some filamentous forms like Nostoc and Anabaena fix nitrogen using heterocysts.
Q28.
Why was the two-kingdom classification (Plantae and Animalia) considered inadequate?
Answer: A. It did not distinguish eukaryotes from prokaryotes, unicellular from multicellular, or photosynthetic from non-photosynthetic organisms
Why: The two-kingdom system failed to distinguish between prokaryotes and eukaryotes, unicellular and multicellular organisms, and photosynthetic (green algae) and non-photosynthetic (fungi) organisms, all of which were grouped together as plants.
Q29.
Which combination correctly matches the fungal class with both its reproductive spore type and an example?
Answer: B. Ascomycetes, ascospores, Penicillium
Why: Ascomycetes produce sexual spores called ascospores formed endogenously in sac-like asci. Penicillium is a classic example. Basidiomycetes produce basidiospores (e.g., Agaricus); deuteromycetes like Alternaria show only asexual conidia.
Q30.
Lichens are used as pollution indicators because
Answer: B. They are extremely sensitive and do not grow in polluted areas
Why: Lichens are highly sensitive to air pollution, particularly sulfur dioxide, and fail to grow in polluted areas. Their absence or decline in an area is used as an indicator of air pollution.
Q31.
Prions, associated with diseases such as mad cow disease, differ from viruses and viroids in that they are
Answer: B. Abnormally folded infectious protein particles with no nucleic acid
Why: Prions are unusual infectious agents composed only of abnormally folded proteins, with no nucleic acid component, unlike viruses (nucleic acid plus protein coat) and viroids (free RNA only).
Q32.
Which feature is shared by chrysophytes and dinoflagellates but distinguishes both from slime moulds?
Answer: A. Both groups are mainly photosynthetic with components in their cell covering
Why: Chrysophytes (diatoms, golden algae) and dinoflagellates are largely photosynthetic, with characteristic coverings (frustule in diatoms, cellulose plates in dinoflagellates), unlike slime moulds, which are heterotrophic saprophytes that engulf decaying matter.
Q33.
Which of these is an example of a symbiotic relationship found in kingdom Fungi (other than a lichen)?
Answer: A. Mycorrhiza, an association between fungi and plant roots
Why: Mycorrhiza is a symbiotic/mutualistic association between fungi and the roots of higher plants. The fungus helps in absorption of water and nutrients, while the plant supplies sugars and organic nutrients.
Q34.
Entamoeba histolytica and Trypanosoma both belong to kingdom Protista but differ mainly in their
Answer: A. Mode of locomotion, pseudopodia versus flagella
Why: Entamoeba is an amoeboid protozoan that moves using pseudopodia, while Trypanosoma is a flagellated protozoan that moves using flagella. Both are heterotrophic, parasitic protists causing disease in humans.
Q35.
A fungal hypha is described as coenocytic. This means
Answer: B. It is multinucleate and lacks septa (cross walls)
Why: A coenocytic hypha is aseptate (lacks septa/cross walls) and multinucleate, as seen in Phycomycetes such as Rhizopus and Mucor. Septate hyphae, by contrast, are divided into individual cells by cross walls.
Q36.
Considering reproduction in Monera, which mechanism allows genetic material transfer between bacteria without cell fusion?
Answer: B. Conjugation, transduction, or transformation
Why: Bacteria primarily reproduce asexually by fission, but genetic material can be transferred between cells through conjugation (direct contact), transduction (via bacteriophages), or transformation (uptake of free DNA), without true cell fusion.