Biological Classification MCQ Questions with Answers

Who proposed the five-kingdom classification of living organisms in 1969?

• Carolus Linnaeus
• Ernst Haeckel
• R.H. Whittaker
• Carl Woese

Answer: R.H. Whittaker. R.H. Whittaker (1969) proposed the five kingdoms: Monera, Protista, Fungi, Plantae and Animalia. Linnaeus had earlier used just two kingdoms, Plantae and Animalia.

Which of the following was NOT one of the criteria Whittaker used to build the five-kingdom system?

• Number of chromosomes in body cells
• Mode of nutrition
• Thallus (body) organisation
• Phylogenetic relationships

Answer: Number of chromosomes in body cells. Whittaker's criteria were cell structure, thallus organisation, mode of nutrition, reproduction and phylogenetic relationships. Chromosome number was not one of them.

Methanogens, which live in the gut of ruminants such as cows and produce methane (biogas), belong to which group?

• Eubacteria
• Cyanobacteria
• Mycoplasma
• Archaebacteria

Answer: Archaebacteria. Methanogens are archaebacteria. Their distinctive cell wall structure helps archaebacteria survive extreme habitats such as hot springs, salty areas and marshes.

In cyanobacteria such as Nostoc and Anabaena, nitrogen is fixed in specialised cells called ______.

• Akinetes
• Heterocysts
• Pellicles
• Gametangia

Answer: Heterocysts. Heterocysts are specialised cells in some filamentous cyanobacteria that fix atmospheric nitrogen.

Which group of organisms has no cell wall at all, includes the smallest living cells known, and can live without oxygen?

• Mycoplasma
• Cyanobacteria
• Diatoms
• Methanogens

Answer: Mycoplasma. Mycoplasma have no cell wall at all. Many are pathogenic in animals and plants.

'Diatomaceous earth', used in polishing and in filtering oils and syrups, comes from the silica-rich cell walls of which protist group?

• Dinoflagellates
• Euglenoids
• Chrysophytes
• Slime moulds

Answer: Chrysophytes. Diatoms belong to the chrysophytes. Their silica walls hardly decay, so over millions of years they built up into thick deposits known as diatomaceous earth.

The 'red tide' seen in some seas is caused by the rapid multiplication of which red dinoflagellate?

• Euglena
• Paramoecium
• Trypanosoma
• Gonyaulax

Answer: Gonyaulax. Gonyaulax multiplies so fast that the sea turns red. The toxins it releases can kill fish and other marine animals.

Euglenoids lack a cell wall. What is the flexible, protein-rich outer layer that covers their body instead?

• Cuticle
• Pellicle
• Capsid
• Chitin coat

Answer: Pellicle. The pellicle gives euglenoids such as Euglena a flexible body. Euglena photosynthesises in sunlight but feeds on smaller organisms without it.

Which statement about slime moulds is correct?

• They are photosynthetic protists with silica walls
• They are autotrophic bacteria that fix nitrogen
• In bad conditions they form fruiting bodies bearing spores with true walls
• They cannot reproduce in any way

Answer: In bad conditions they form fruiting bodies bearing spores with true walls. Slime moulds are saprophytic protists. Their spores have true walls, survive harsh conditions for years and spread through air currents.

African sleeping sickness is caused by which flagellated protozoan?

• Trypanosoma
• Plasmodium
• Paramoecium
• Amoeba

Answer: Trypanosoma. Trypanosoma is a flagellated protozoan. Plasmodium, a sporozoan, causes malaria. Paramoecium is ciliated, and Amoeba moves using pseudopodia.

Find the odd one out by fungal class.

• Mucor
• Rhizopus
• Albugo
• Agaricus

Answer: Agaricus. Mucor, Rhizopus and Albugo are phycomycetes, with aseptate (coenocytic) mycelium. Agaricus, a mushroom, is a basidiomycete.

The cell wall of most fungi is mainly made of:

• Cellulose
• Chitin and polysaccharides
• Peptidoglycan
• Silica

Answer: Chitin and polysaccharides. Fungal cell walls are built from chitin and polysaccharides. Peptidoglycan is found in bacteria, and silica in diatoms.

Neurospora, used extensively in biochemical and genetic research, belongs to which class of fungi?

• Phycomycetes
• Basidiomycetes
• Ascomycetes
• Deuteromycetes

Answer: Ascomycetes. Neurospora is an ascomycete (sac fungus). Sac fungi produce ascospores inside sac-like asci.

Which class of fungi is nicknamed the 'imperfect fungi' because only their asexual or vegetative stages are known?

• Deuteromycetes
• Ascomycetes
• Basidiomycetes
• Phycomycetes

Answer: Deuteromycetes. Deuteromycetes such as Alternaria, Colletotrichum and Trichoderma are 'imperfect'. Once their sexual stage is found, they are moved to Ascomycetes or Basidiomycetes.

Puccinia (rust fungus) and Ustilago (smut fungus) belong to which class?

• Ascomycetes
• Phycomycetes
• Deuteromycetes
• Basidiomycetes

Answer: Basidiomycetes. Rusts and smuts are basidiomycetes, along with mushrooms and bracket fungi. They have no sex organs, and basidiospores form outside a club-shaped basidium.

Albugo, a phycomycete fungus, is a well-known parasite of which crop plant?

• Wheat
• Mustard
• Rice
• Potato

Answer: Mustard. Albugo causes white rust on mustard. It is the standard example of a parasitic phycomycete.

Who described the infectious agent of tobacco mosaic disease as 'contagium vivum fluidum' (infectious living fluid)?

• Dmitri Ivanowsky
• W.M. Stanley
• M.W. Beijerinck
• T.O. Diener

Answer: M.W. Beijerinck. Beijerinck (1898) gave the term. Ivanowsky (1892) first found the agent was smaller than bacteria, and Stanley later showed viruses could be crystallised.

Viroids, discovered by T.O. Diener in 1971 as the cause of potato spindle tuber disease, differ from viruses because they:

• Are free RNA with no protein coat
• Contain DNA inside a lipid envelope
• Are made only of protein
• Have a cell wall made of chitin

Answer: Are free RNA with no protein coat. A viroid is a small, free RNA molecule with no protein coat (capsid). A virus always has a protein coat around its genetic material.

The genetic material of bacteriophages (viruses that infect bacteria) is usually:

• Single-stranded RNA
• Double-stranded RNA
• Single-stranded DNA
• Double-stranded DNA

Answer: Double-stranded DNA. Bacteriophages are usually double-stranded DNA viruses. Plant viruses generally carry single-stranded RNA.

A lichen is a symbiotic partnership. What are its algal and fungal partners called, in that order?

• Mycobiont and phycobiont
• Phycobiont and mycobiont
• Heterocyst and hypha
• Plasmodium and sporangium

Answer: Phycobiont and mycobiont. The alga (phycobiont) makes food, and the fungus (mycobiont) gives shelter and absorbs water and minerals. Lichens do not grow in polluted air, so they are good pollution indicators.