Biological Classification

What to remember

• Whittaker (1969) proposed five kingdoms: Monera, Protista, Fungi, Plantae and Animalia, using cell structure, body organisation, mode of nutrition, reproduction and phylogenetic relationships.
• Monera are prokaryotes; Protista, Fungi, Plantae and Animalia are eukaryotes; fungal cell walls contain chitin, plant cell walls contain cellulose, and animal cells have no cell wall.
• Fungi are grouped into Phycomycetes, Ascomycetes, Basidiomycetes and Deuteromycetes; spores are zygospores, ascospores, basidiospores and conidia respectively, and Deuteromycetes have no known sexual stage.
• Viruses have either DNA or RNA inside a protein coat and are inert outside a host cell; viroids are free RNA without a protein coat; prions are abnormally folded infectious proteins; lichens are algae plus fungi living together.

History of classification

Aristotle was the earliest to attempt a scientific basis for classification. He used simple morphological characters. He classified plants into trees, shrubs and herbs. He divided animals into two groups: those with red blood and those without red blood.

Linnaeus later gave the two-kingdom system, Plantae and Animalia. This system did not distinguish between the eukaryotes and prokaryotes, unicellular and multicellular organisms, and photosynthetic (green algae) and non-photosynthetic (fungi) organisms. Bacteria, fungi, and algae were all placed in plants, although they are very different from plants. For this reason, other systems were proposed that took into account cell structure, nature of the cell wall, mode of nutrition, habitat, methods of reproduction and evolutionary relationships.

Five-kingdom classification

R.H. Whittaker (1969) proposed a five-kingdom classification. The kingdoms are Monera, Protista, Fungi, Plantae and Animalia. The main criteria were cell structure, thallus organisation, mode of nutrition, reproduction and phylogenetic relationships.

The five-kingdom system shows evolutionary relationships. Viruses, viroids and lichens were not placed in any of the five kingdoms.

Three domains of life

Later work on the molecular features of cells led to a system of three domains: Archaea, Bacteria and Eukarya. The archaebacteria are placed in the domain Archaea and the true bacteria (eubacteria) are placed in the domain Bacteria. All eukaryotes are placed in the domain Eukarya.

Kingdom Monera

Monera includes all bacteria. Bacteria are the sole members of this kingdom. They are the most abundant micro-organisms and occur almost everywhere, from hot springs to deep oceans. They are unicellular and prokaryotic. They show the most extensive metabolic diversity. Some are autotrophic (photosynthetic or chemosynthetic), and most are heterotrophic.

Archaebacteria. These bacteria live in harsh conditions. They have a different cell wall structure, which helps them survive in extreme conditions. Three kinds are:

• Halophiles: live in extreme salty areas.
• Thermoacidophiles: live in hot springs, which are hot and acidic.
• Methanogens: live in marshy areas and in the guts of several ruminant animals such as cows and buffaloes, and produce methane (biogas) from dung.

Eubacteria (true bacteria). They have a rigid cell wall and a flagellum if motile. The shapes are:

Cyanobacteria (blue-green algae). They have chlorophyll a similar to that in green plants and are photosynthetic autotrophs. They are unicellular, colonial or filamentous, occur in freshwater, marine water or on land, and often form blooms in polluted water bodies. Some colonies are surrounded by a gelatinous sheath. Some, like Nostoc and Anabaena, can fix atmospheric nitrogen in specialised cells called heterocysts.

Chemosynthetic autotrophic bacteria. They oxidise various inorganic substances such as nitrates, nitrites and ammonia and use the released energy for their ATP production. They play a great role in recycling nutrients like nitrogen, phosphorus, iron and sulphur.

Heterotrophic bacteria. They are the most abundant in nature. The majority are important decomposers. They are helpful in making curd from milk, production of antibiotics, fixing nitrogen in legume roots and so on. Some are pathogens causing damage to human beings, crops, farm animals and pets. Examples of diseases are cholera, typhoid, tetanus and citrus canker.

Reproduction in bacteria. Bacteria reproduce mainly by binary fission. Sometimes, under unfavourable conditions, they produce spores. They also reproduce by a primitive type of DNA transfer from one bacterium to another.

Mycoplasma. These organisms completely lack a cell wall. They are the smallest living cells known and can survive without oxygen. Many mycoplasma are pathogenic in animals and plants.

Kingdom Protista

All single-celled eukaryotes are placed under Protista. The boundaries of this kingdom are not well defined. Protists are primarily aquatic. They reproduce asexually and sexually by a process involving cell fusion and zygote formation.

Chrysophytes. This group includes diatoms and golden algae (desmids). They are found in fresh water as well as in marine environments. They are microscopic and float passively in water currents (plankton). Most are photosynthetic. In diatoms the cell walls form two thin overlapping shells, which fit together as in a soap box. The walls are embedded with silica and thus the walls are indestructible. Thus, diatoms have left behind a large amount of cell wall deposits in their habitat; this accumulation over billions of years is referred to as "diatomaceous earth". Being gritty, this soil is used in polishing, filtration of oils and syrups. Diatoms are the chief producers in the oceans.

Dinoflagellates. These are mostly marine and photosynthetic. They appear yellow, green, brown, blue or red depending on the main pigments present in their cells. The cell wall has stiff cellulose plates on the outer surface. Most have two flagella; one lies longitudinally and the other transversely in a furrow between the wall plates. Very often, red dinoflagellates (for example, Gonyaulax) undergo such rapid multiplication that they make the sea appear red in colour (red tides). Toxins released may even kill other marine animals such as fishes.

Euglenoids. Majority of them are freshwater organisms found in stagnant water. Instead of a cell wall, they have a protein-rich layer called the pellicle, which makes their body flexible. They have two flagella, a short and a long one. Though they are photosynthetic in the presence of sunlight, when deprived of sunlight they behave like heterotrophs by predating on other smaller organisms. Interestingly, the pigments of euglenoids are identical to those found in the higher plants. Example: Euglena.

Slime moulds. Slime moulds are saprophytic protists. The body moves along decaying twigs and leaves, engulfing organic material. Under suitable conditions, they form an aggregation called a plasmodium, which may grow and spread over several feet. Under unfavourable conditions, the plasmodium differentiates and forms fruiting bodies bearing spores at their tips. The spores possess true walls. They are extremely resistant and survive for many years, even under adverse conditions. The spores are dispersed by air currents.

Protozoans. All protozoans are heterotrophs and live as predators or parasites. They are believed to be primitive relatives of animals. There are four major groups.

In ciliated protozoans, the coordinated movement of rows of cilia causes the water laden with food to be steered into the gullet.

Kingdom Fungi

Fungi are a unique kingdom of heterotrophic organisms. They show a great diversity in morphology and habitat. Some fungi are parasites on plants and animals. Except for yeast, which is unicellular, fungi are filamentous. Their bodies consist of long, slender thread-like structures called hyphae. The network of hyphae is known as mycelium. Some hyphae are continuous tubes filled with multinucleated cytoplasm; these are called coenocytic hyphae. Others have septae or cross walls in their hyphae (septate hyphae). The cell walls of fungi are made of chitin and polysaccharides.

Nutrition. Most fungi are heterotrophic and absorb soluble organic matter from dead substrates and hence are called saprophytes. Those that depend on living plants and animals are called parasites. They can also live as symbionts, in association with algae as lichens and with roots of higher plants as mycorrhiza.

Reproduction. Fungi can reproduce by vegetative means (fragmentation, fission and budding), by asexual means (spores called conidia, zoospores or sporangiospores) and by sexual means (oospores, ascospores and basidiospores). The sexual cycle has three steps:

• 1. Plasmogamy: fusion of protoplasms between two motile or non-motile gametes.
• 2. Karyogamy: fusion of two nuclei.
• 3. Meiosis in the zygote, resulting in haploid spores.

In some fungi, the fusion of two haploid cells does not immediately lead to the fusion of nuclei. The cell has two nuclei in the same cell, called the dikaryon stage (n + n). Later the nuclei fuse (karyogamy) and meiosis follows. This dikaryon stage is seen in Ascomycetes and Basidiomycetes. In Phycomycetes, karyogamy follows plasmogamy quickly.

Phycomycetes are found in aquatic habitats, on decaying wood in moist places, or as obligate parasites on plants. Zoospores or aplanospores are formed endogenously in a sporangium. A zygospore is formed by fusion of two gametes, which may be isogamous, anisogamous or oogamous. Rhizopus is a bread mould, and Albugo is a parasite on mustard.

Ascomycetes are commonly called sac fungi. They are unicellular (yeast) or multicellular (Penicillium). They can be saprophytic, decomposers, parasitic or coprophilous (growing on dung). Conidia are produced exogenously on conidiophores. Ascospores are produced endogenously in sac-like asci, which are arranged in fruiting bodies called ascocarps. Neurospora is used extensively in biochemical and genetic work.

Basidiomycetes include mushrooms, bracket fungi and puffballs. They grow in soil, on logs and tree stumps, and in living plant bodies as parasites, as in rusts and smuts. Sex organs are absent, but plasmogamy is brought about by fusion of two vegetative or somatic cells of different strains. The resulting structure is dikaryotic and gives rise to the basidium. Karyogamy and meiosis take place in the basidium, producing four basidiospores. Basidia are arranged in basidiocarps.

Deuteromycetes are commonly known as imperfect fungi because only the asexual or vegetative phases are known. When the sexual forms of these fungi were discovered they were moved into Ascomycetes or Basidiomycetes. Many of them are decomposers of litter and help in mineral cycling.

Kingdom Plantae and Kingdom Animalia

Plantae includes all eukaryotic chlorophyll-containing organisms commonly called plants. The plant cell has a cell wall made of cellulose. Plantae includes algae, bryophytes, pteridophytes, gymnosperms and angiosperms. The life cycle has two distinct phases, the diploid sporophyte and the haploid gametophyte, which alternate. This is called alternation of generations.

Animalia includes all multicellular eukaryotic organisms that are heterotrophic and lack a cell wall. They directly or indirectly depend on plants for food. They digest their food in an internal cavity and store food reserves as glycogen or fat. Their mode of nutrition is holozoic, that is, by ingestion of food. Higher forms show sexual reproduction by copulation of male and female followed by embryological development.

Viruses, viroids, prions and lichens

The name virus means venom or poisonous fluid. D.J. Ivanowsky (1892) recognised that the causal organism of the mosaic disease of tobacco could pass through bacteria-proof filters. M.W. Beijerinck (1898) showed that the extract of infected tobacco plants could cause infection in healthy plants and called the fluid Contagium vivum fluidum (infectious living fluid). W.M. Stanley (1935) showed that viruses could be crystallised, and the crystals consist largely of proteins. Viruses are inert outside their specific host cell.

Viruses are obligate parasites. They have a protein coat called the capsid, made of small subunits called capsomeres, which protects the nucleic acid. The genetic material is either RNA or DNA, never both. In plant viruses, the genetic material is mostly single-stranded RNA. In animal viruses, it is single-stranded or double-stranded RNA or double-stranded DNA. Bacteriophages, which infect bacteria, have mostly double-stranded DNA, and look tadpole-like with a head and a tail.

Viroids. T.O. Diener (1971) discovered an infectious agent smaller than viruses that caused potato spindle tuber disease. It was found to be a free RNA of low molecular weight, without the protein coat, and was called a viroid.

Prions. Prions are abnormally folded infectious proteins. They cause neurodegenerative diseases, such as bovine spongiform encephalopathy (BSE, mad cow disease) in cattle and Creutzfeldt-Jakob disease (CJD) in humans.

Lichens. Lichens are symbiotic associations between algae and fungi. The algal component is the phycobiont and is autotrophic. The fungal component is the mycobiont and is heterotrophic. Algae prepare food for the fungi, and fungi provide shelter and absorb nutrients and water for the algae. Lichens are good pollution indicators because they do not grow in polluted areas.

NEET traps

• 1. Archaebacteria vs eubacteria: Halophiles, thermoacidophiles and methanogens are archaebacteria; cocci, bacilli, vibrios and spirilla are eubacteria.
• 2. Mycoplasma: They are bacteria with no cell wall; do not say they have a peptidoglycan wall.
• 3. Heterocysts: They are specialised cells of cyanobacteria (Nostoc, Anabaena) for nitrogen fixation, not for reproduction.
• 4. Diatoms vs dinoflagellates: Diatoms have silica walls and form diatomaceous earth; dinoflagellates have cellulose plates, two flagella and cause red tides.
• 5. Euglenoid wall: Euglena has a pellicle, not a cell wall, and can be photosynthetic or heterotrophic.
• 6. Slime mould body: The plasmodium is a mass of protoplasm; spores form on fruiting bodies and have true walls.
• 7. Spores of fungi: Zygospore is Phycomycetes, ascospore is Ascomycetes, basidiospore is Basidiomycetes. Conidia occur in Ascomycetes and Deuteromycetes.
• 8. Deuteromycetes: Called imperfect fungi because the sexual stage is not known; Penicillium is an Ascomycete, while Alternaria is a Deuteromycete.
• 9. Plasmogamy vs karyogamy: Plasmogamy is fusion of cytoplasm and karyogamy is fusion of nuclei; the dikaryon stage lies between them in Ascomycetes and Basidiomycetes.
• 10. Viruses vs viroids vs prions: Viruses have protein coat plus DNA or RNA; viroids are only RNA; prions are only protein.

One-liners

• 1. Aristotle divided animals into those with red blood and those without red blood.
• 2. Linnaeus gave the two-kingdom system, Plantae and Animalia.
• 3. Whittaker gave the five-kingdom system in 1969.
• 4. Monera cells are prokaryotic and have a non-cellulosic cell wall.
• 5. Methanogens produce methane from the dung of ruminants.
• 6. Cyanobacteria fix nitrogen in heterocysts.
• 7. Mycoplasma are the smallest living cells and have no cell wall.
• 8. Bacteria reproduce mainly by binary fission.
• 9. Diatoms have silica walls, which form diatomaceous earth.
• 10. Gonyaulax multiplies rapidly to cause red tides.
• 11. Slime moulds form a plasmodium and spore-bearing fruiting bodies.
• 12. Plasmodium is a sporozoan that causes malaria.
• 13. Fungal cell walls contain chitin and polysaccharides.
• 14. Neurospora is used in biochemical and genetic work.
• 15. Lichens are algae (phycobiont) plus fungi (mycobiont) and indicate low pollution.

Practice questions

1. Who classified animals into those with red blood and those without red blood?

   1. Linnaeus
   2. W.M. Stanley
   3. Aristotle
   4. R.H. Whittaker
   Answer

   C. Aristotle

   Aristotle used simple morphological characters and divided animals into those with red blood and those without.

2. The five-kingdom classification was proposed by

   1. R.H. Whittaker
   2. T.O. Diener
   3. D.J. Ivanowsky
   4. Linnaeus
   Answer

   A. R.H. Whittaker

   R.H. Whittaker proposed the five kingdoms Monera, Protista, Fungi, Plantae and Animalia in 1969.

3. Which archaebacteria live in marshy areas and in the guts of ruminants and produce methane?

   1. Thermoacidophiles
   2. Methanogens
   3. Mycoplasma
   4. Halophiles
   Answer

   B. Methanogens

   Methanogens produce methane (biogas) from dung and live in marshy areas and the guts of ruminants.

4. Specialised cells called heterocysts, which fix atmospheric nitrogen, are found in

   1. Euglena
   2. diatoms
   3. Mycoplasma
   4. Nostoc
   Answer

   D. Nostoc

   Heterocysts are found in cyanobacteria such as Nostoc and Anabaena.

5. Which of the following organisms completely lacks a cell wall and is the smallest living cell known?

   1. Spirillum
   2. Mycoplasma
   3. Vibrio
   4. Cyanobacterium
   Answer

   B. Mycoplasma

   Mycoplasma lack a cell wall, are the smallest known living cells and can survive without oxygen.

6. Diatomaceous earth is formed from the cell wall deposits of

   1. diatoms
   2. euglenoids
   3. slime moulds
   4. dinoflagellates
   Answer

   A. diatoms

   Diatom walls are embedded with silica and are indestructible, forming diatomaceous earth over a long time.

7. Red tides in the sea are caused by rapid multiplication of

   1. Euglena
   2. Paramecium
   3. Plasmodium
   4. Gonyaulax
   Answer

   D. Gonyaulax

   Gonyaulax, a red dinoflagellate, multiplies rapidly and makes the sea look red.

8. A protein-rich layer called the pellicle, in place of a cell wall, is found in

   1. dinoflagellates
   2. slime moulds
   3. euglenoids
   4. diatoms
   Answer

   C. euglenoids

   Euglenoids have a pellicle, which makes the body flexible.

9. The malarial parasite Plasmodium is placed under

   1. sporozoans
   2. amoeboid protozoans
   3. flagellated protozoans
   4. ciliated protozoans
   Answer

   A. sporozoans

   Sporozoans have an infectious spore-like stage in the life cycle. Plasmodium is a sporozoan.

10. Sexual spores of Ascomycetes are called

    1. zoospores
    2. ascospores
    3. basidiospores
    4. zygospores
    Answer

    B. ascospores

    Ascomycetes produce ascospores endogenously in asci.

11. Rhizopus, the bread mould, belongs to

    1. Ascomycetes
    2. Basidiomycetes
    3. Phycomycetes
    4. Deuteromycetes
    Answer

    C. Phycomycetes

    Rhizopus, Mucor and Albugo are Phycomycetes with aseptate coenocytic mycelium.

12. Fungi of which group are called imperfect fungi because only the asexual phase is known?

    1. Ascomycetes
    2. Phycomycetes
    3. Basidiomycetes
    4. Deuteromycetes
    Answer

    D. Deuteromycetes

    Deuteromycetes are called imperfect fungi because their sexual stage is not known.

13. Which of the following is a member of Basidiomycetes?

    1. Alternaria
    2. Neurospora
    3. Mucor
    4. Puccinia
    Answer

    D. Puccinia

    Puccinia is a rust fungus in Basidiomycetes. Neurospora is an Ascomycete, Mucor a Phycomycete and Alternaria a Deuteromycete.

14. Which fungus is used extensively in biochemical and genetic work?

    1. Ustilago
    2. Agaricus
    3. Neurospora
    4. Albugo
    Answer

    C. Neurospora

    Neurospora is an Ascomycete used extensively in biochemical and genetic studies.

15. The genetic material of tobacco mosaic virus (TMV) is

    1. single-stranded RNA
    2. double-stranded DNA
    3. single-stranded DNA
    4. double-stranded RNA
    Answer

    A. single-stranded RNA

    Plant viruses mostly have single-stranded RNA as the genetic material.

16. The infectious agent of potato spindle tuber disease, a free RNA without a protein coat, is a

    1. bacterium
    2. viroid
    3. virus
    4. prion
    Answer

    B. viroid

    T.O. Diener discovered the viroid, which is free RNA of low molecular weight.

17. Given below are two statements: Statement I: Cell structure and mode of nutrition were among the criteria used by Whittaker. Statement II: Viruses, viroids and lichens were not placed in any of the five kingdoms.

    1. Both Statement I and Statement II are correct
    2. Both Statement I and Statement II are incorrect
    3. Statement I is correct but Statement II is incorrect
    4. Statement I is incorrect but Statement II is correct
    Answer

    A. Both Statement I and Statement II are correct

    Both are correct.

18. Given below are two statements: Statement I: The cell wall of fungi is made of cellulose. Statement II: Mycoplasma have a rigid cell wall.

    1. Both Statement I and Statement II are correct
    2. Both Statement I and Statement II are incorrect
    3. Statement I is correct but Statement II is incorrect
    4. Statement I is incorrect but Statement II is correct
    Answer

    B. Both Statement I and Statement II are incorrect

    Fungal walls have chitin and polysaccharides, and Mycoplasma completely lack a cell wall.

19. Given below are two statements: Statement I: Methanogens are archaebacteria found in the guts of ruminants. Statement II: Halophiles live in hot and acidic springs.

    1. Both Statement I and Statement II are correct
    2. Both Statement I and Statement II are incorrect
    3. Statement I is correct but Statement II is incorrect
    4. Statement I is incorrect but Statement II is correct
    Answer

    C. Statement I is correct but Statement II is incorrect

    Halophiles live in extremely salty areas. Hot springs are the habitat of thermoacidophiles.

20. Given below are two statements: Statement I: Diatoms have cellulose walls that are easily destroyed. Statement II: Diatoms are the chief producers in the oceans.

    1. Both Statement I and Statement II are correct
    2. Both Statement I and Statement II are incorrect
    3. Statement I is correct but Statement II is incorrect
    4. Statement I is incorrect but Statement II is correct
    Answer

    D. Statement I is incorrect but Statement II is correct

    Diatom walls contain silica and are indestructible, so Statement I is incorrect.

21. Given below are two statements: Statement I: Slime moulds form an aggregation called a plasmodium. Statement II: Their spores have true walls and are dispersed by air currents.

    1. Both Statement I and Statement II are correct
    2. Both Statement I and Statement II are incorrect
    3. Statement I is correct but Statement II is incorrect
    4. Statement I is incorrect but Statement II is correct
    Answer

    A. Both Statement I and Statement II are correct

    Both are correct.

22. Given below are two statements: Statement I: In Phycomycetes, karyogamy follows plasmogamy quickly. Statement II: The dikaryon stage is absent in Basidiomycetes.

    1. Both Statement I and Statement II are correct
    2. Both Statement I and Statement II are incorrect
    3. Statement I is correct but Statement II is incorrect
    4. Statement I is incorrect but Statement II is correct
    Answer

    C. Statement I is correct but Statement II is incorrect

    The dikaryon stage is seen in Ascomycetes and Basidiomycetes, so Statement II is incorrect.

23. Given below are two statements: Statement I: A virus contains both DNA and RNA. Statement II: Viruses are inert outside their specific host cell.

    1. Both Statement I and Statement II are correct
    2. Both Statement I and Statement II are incorrect
    3. Statement I is correct but Statement II is incorrect
    4. Statement I is incorrect but Statement II is correct
    Answer

    D. Statement I is incorrect but Statement II is correct

    A virus has either DNA or RNA, never both. Statement II is correct.

24. Which of the following statements are correct? 1. Lichens are symbiotic associations of algae and fungi. 2. The fungal partner of a lichen is called the phycobiont. 3. Lichens are good indicators of pollution.

    1. 1 and 2 only
    2. 1 and 3 only
    3. 2 and 3 only
    4. 1, 2 and 3
    Answer

    B. 1 and 3 only

    The fungal partner is the mycobiont, and the algal partner is the phycobiont.

25. Which of the following statements are correct? 1. Prions are abnormally folded infectious proteins. 2. Bovine spongiform encephalopathy is a prion disease. 3. Viroids lack a protein coat.

    1. 1 and 2 only
    2. 1 and 3 only
    3. 2 and 3 only
    4. 1, 2 and 3
    Answer

    D. 1, 2 and 3

    All three statements are correct.

26. Given below are two statements: Statement I: Euglenoids have two flagella, one short and one long. Statement II: Euglenoids behave like heterotrophs when deprived of sunlight.

    1. Both Statement I and Statement II are correct
    2. Both Statement I and Statement II are incorrect
    3. Statement I is correct but Statement II is incorrect
    4. Statement I is incorrect but Statement II is correct
    Answer

    A. Both Statement I and Statement II are correct

    Both are correct.

27. Assertion (A): Cyanobacteria such as Nostoc can fix atmospheric nitrogen. Reason (R): They have specialised cells called heterocysts.

    1. Both A and R are true and R is the correct explanation of A
    2. Both A and R are true but R is not the correct explanation of A
    3. A is true but R is false
    4. A is false but R is true
    Answer

    A. Both A and R are true and R is the correct explanation of A

    Nitrogen fixation takes place in heterocysts, so R explains A.

28. Assertion (A): Diatoms are the chief producers in the oceans. Reason (R): The walls of diatoms are embedded with silica.

    1. Both A and R are true and R is the correct explanation of A
    2. Both A and R are true but R is not the correct explanation of A
    3. A is true but R is false
    4. A is false but R is true
    Answer

    B. Both A and R are true but R is not the correct explanation of A

    Both are true, but silica walls do not explain why diatoms are major producers; they are photosynthetic.

29. Assertion (A): Lichens are good pollution indicators. Reason (R): Lichens grow well in polluted areas.

    1. Both A and R are true and R is the correct explanation of A
    2. Both A and R are true but R is not the correct explanation of A
    3. A is true but R is false
    4. A is false but R is true
    Answer

    C. A is true but R is false

    Lichens do not grow in polluted areas, so R is false.

30. Assertion (A): Mycoplasma can survive without oxygen. Reason (R): Mycoplasma completely lack a cell wall.

    1. Both A and R are true and R is the correct explanation of A
    2. Both A and R are true but R is not the correct explanation of A
    3. A is true but R is false
    4. A is false but R is true
    Answer

    B. Both A and R are true but R is not the correct explanation of A

    Both are true, but the lack of a wall does not explain survival without oxygen.

31. Assertion (A): Deuteromycetes are called imperfect fungi. Reason (R): Their sexual stage is well known.

    1. Both A and R are true and R is the correct explanation of A
    2. Both A and R are true but R is not the correct explanation of A
    3. A is true but R is false
    4. A is false but R is true
    Answer

    C. A is true but R is false

    The sexual stage of Deuteromycetes is not known, so R is false.

32. Assertion (A): The two-kingdom system of Linnaeus separated prokaryotes from eukaryotes. Reason (R): Bacteria, fungi and algae were all placed in the plant kingdom in that system.

    1. Both A and R are true and R is the correct explanation of A
    2. Both A and R are true but R is not the correct explanation of A
    3. A is true but R is false
    4. A is false but R is true
    Answer

    D. A is false but R is true

    The two-kingdom system did not separate prokaryotes from eukaryotes. R is true.

33. Match List I with List II. List I: a. Halophiles b. Thermoacidophiles c. Methanogens d. Cyanobacteria List II: i. Marshy areas and guts of ruminants ii. Extremely salty areas iii. Heterocysts iv. Hot springs

    1. a-iv, b-ii, c-i, d-iii
    2. a-i, b-iv, c-ii, d-iii
    3. a-ii, b-iv, c-i, d-iii
    4. a-ii, b-iv, c-iii, d-i
    Answer

    C. a-ii, b-iv, c-i, d-iii

    Halophiles: salty areas; thermoacidophiles: hot springs; methanogens: marshy areas and ruminant guts; cyanobacteria: heterocysts.

34. Match List I with List II. List I: a. Diatoms b. Dinoflagellates c. Euglenoids d. Slime moulds List II: i. Pellicle ii. Plasmodium iii. Silica wall iv. Red tide

    1. a-iii, b-i, c-iv, d-ii
    2. a-iii, b-iv, c-i, d-ii
    3. a-iv, b-iii, c-i, d-ii
    4. a-iii, b-iv, c-ii, d-i
    Answer

    B. a-iii, b-iv, c-i, d-ii

    Diatoms: silica wall; dinoflagellates: red tide; euglenoids: pellicle; slime moulds: plasmodium.

35. Match List I with List II. List I: a. Amoeba b. Trypanosoma c. Paramecium d. Plasmodium List II: i. Cilia ii. Sporozoans iii. Pseudopodia iv. Flagellated protozoan

    1. a-iii, b-iv, c-i, d-ii
    2. a-i, b-iv, c-iii, d-ii
    3. a-iii, b-iv, c-ii, d-i
    4. a-iii, b-i, c-iv, d-ii
    Answer

    A. a-iii, b-iv, c-i, d-ii

    Amoeba: pseudopodia; Trypanosoma: flagellated; Paramecium: cilia; Plasmodium: sporozoan.

36. Match List I with List II. List I: a. Rhizopus b. Penicillium c. Puccinia d. Alternaria List II: i. Basidiomycetes ii. Deuteromycetes iii. Ascomycetes iv. Phycomycetes

    1. a-i, b-iii, c-iv, d-ii
    2. a-iv, b-i, c-iii, d-ii
    3. a-iii, b-iv, c-i, d-ii
    4. a-iv, b-iii, c-i, d-ii
    Answer

    D. a-iv, b-iii, c-i, d-ii

    Rhizopus: Phycomycetes; Penicillium: Ascomycetes; Puccinia: Basidiomycetes; Alternaria: Deuteromycetes.

37. Match List I with List II. List I: a. Tobacco mosaic virus b. Bacteriophage c. Viroid d. Prion List II: i. Tadpole-like virus with double-stranded DNA ii. Protein only iii. Free RNA, potato spindle tuber disease iv. Plant virus with single-stranded RNA

    1. a-iv, b-ii, c-iii, d-i
    2. a-iv, b-i, c-iii, d-ii
    3. a-iii, b-i, c-iv, d-ii
    4. a-i, b-iv, c-iii, d-ii
    Answer

    B. a-iv, b-i, c-iii, d-ii

    TMV: plant virus with single-stranded RNA; bacteriophage: tadpole-like with double-stranded DNA; viroid: free RNA; prion: protein only.

38. Match List I with List II. List I: a. Aristotle b. D.J. Ivanowsky c. M.W. Beijerinck d. W.M. Stanley List II: i. Crystallised viruses ii. Contagium vivum fluidum iii. Passage through bacteria-proof filters iv. Animals with and without red blood

    1. a-iv, b-iii, c-ii, d-i
    2. a-iv, b-ii, c-iii, d-i
    3. a-iii, b-iv, c-ii, d-i
    4. a-iv, b-i, c-ii, d-iii
    Answer

    A. a-iv, b-iii, c-ii, d-i

    Aristotle: red blood or not; Ivanowsky: bacteria-proof filters; Beijerinck: Contagium vivum fluidum; Stanley: crystallised viruses.

39. A green scum appears in a polluted pond. Under the microscope, filaments with specialised nitrogen-fixing cells called heterocysts are seen. The organism is most likely

    1. Paramecium
    2. Euglena
    3. Gonyaulax
    4. Anabaena
    Answer

    D. Anabaena

    Heterocysts occur in filamentous cyanobacteria such as Anabaena and Nostoc.

40. The sea near a coast turns red and many fish die. The most likely cause is

    1. growth of slime moulds
    2. a bloom of diatoms
    3. rapid multiplication of dinoflagellates such as Gonyaulax
    4. growth of Mycoplasma
    Answer

    C. rapid multiplication of dinoflagellates such as Gonyaulax

    Red dinoflagellates cause red tides, and their toxins may kill marine animals.

41. A bacterium is isolated from a hot and acidic spring. It is most likely a

    1. thermoacidophile
    2. halophile
    3. methanogen
    4. coccus-shaped eubacterium
    Answer

    A. thermoacidophile

    Thermoacidophiles are archaebacteria that live in hot and acidic springs.

42. A fungus shows aseptate, coenocytic mycelium and forms zygospores. It belongs to

    1. Deuteromycetes
    2. Ascomycetes
    3. Phycomycetes
    4. Basidiomycetes
    Answer

    C. Phycomycetes

    Aseptate coenocytic mycelium and zygospores are features of Phycomycetes.

43. A fungus was known only by its conidia. Later, sexual spores formed in sac-like asci inside ascocarps were found in it. To which group should it now be moved?

    1. Phycomycetes
    2. Basidiomycetes
    3. Protista
    4. Ascomycetes
    Answer

    D. Ascomycetes

    Sexual spores in asci mean it is an Ascomycete, so it leaves Deuteromycetes.

44. Cattle and humans can develop a fatal neurodegenerative disease, such as BSE or Creutzfeldt-Jakob disease. The infectious agent is a

    1. Mycoplasma
    2. prion
    3. virus with a capsid
    4. viroid
    Answer

    B. prion

    Prions are abnormally folded infectious proteins that cause these diseases.

45. Lichens are abundant on a clean hillside but are absent in an industrial area. What is the best inference?

    1. Lichens are only heterotrophic
    2. The fungal partner is photosynthetic
    3. Lichens need pollution to grow
    4. Lichens are sensitive to pollution and act as indicators
    Answer

    D. Lichens are sensitive to pollution and act as indicators

    Lichens do not grow in polluted areas, so they are pollution indicators.