Biology,  Botony,  MCQ


1. Which one belongs to monera?

(a) Amoeba

(b) Escherichia

(c) Gelidium

(d) Spirogyra.

Answer and Explanation:

1. (b): All prokaryotic organisms comes under Kingdom monera. Escherichia coli is a bacteria. Monera includes bacteria, mycoplasmas, cyanobacteria (blue green alga) and actinomycetes.

2. The main difference in Gram (+) ve and Gram (-) ve bacteria resides in their

(a) cell wall

(b) cell membrane

(c) cytoplasm

(d) flagella.

Answer and Explanation:

2. (a): Danish bacteriologists Christian Gram for the first time classified bacteria on the basis of the cell wall into two groups – gram +ve and gram -ve by staining with crystal violet and safranin. Gram +ve cell walls are less complex with peptidoglycan compounds and proteins and no lipids in the cell wall. Whereas in Gram -ve cell walls are more complex with peptidoglycan compounds, phospholipids and lipopolysaccharides and contains 20% lipids.

3. A non-photosynthetic aerobic nitrogen fixing soil bacterium is

(a) Rhizobium

(b) Clostridium

(c) Azotobacter

(d) Klebsiella.

Answer and Explanation:

3. (c): A non-photosynthetic aerobic nitrogen fixing soil bacterium is Azotobacter. Azotobacter is free living soil bacteria that are able to pick up dinitrogen from the soil and fixes it into organic nitrogenous material like amino acid.

4. Name the organisms which do not derive energy directly or indirectly from sun

(a) chemosynthetic bacteria

(b) pathogenic bacteria

(c) symbiotic bacteria

(d) mould.

Answer and Explanation:

4. (a): Chemosynthetic bacteria do not derive energy directly or indirectly from sun. The source of energy of these bacteria is inorganic substances. They utilise the energy liberated by oxidation of inorganic compounds and synthesize organic compounds.

5. Bacteria lack alternation of generation because there is

(a) neither syngamy nor reduction division

(b) distinct chromosomes are absent

(c) no conjugation

(d) no exchange of genetic material.

Answer and Explanation:

5. (a): In sexual reproduction, syngamy and meiotic division takes place but in bacteria, during sexual reproduction there is no formation of gametes hence no syngamy and reduction division occurs, bacteria lack alternation of generation. Conjugation and exchange of genetic material takes place in bacteria.

6. Escherichia coli is used extensively in biological research as it is

(a) easily cultured

(b) easily available

(c) easy to handle

(d) easily multiplied in host

Answer and Explanation:

6. (a): E. coli bacteria acts as a human symbionts and it is found in human intestine, synthesize vitamin K and B and also help in food fermentation. It is easily cultured in any nutrient medium in the laboratory.

7. Genophore/bacterial genome or nucleoid is made of

(a) histones and nonhistones

(b) RNA and histones

(c) a single double stranded DNA

(d) a single stranded DNA.

Answer and Explanation:

7. (c): Bacteria has no nuclear membrane hence it is called as nucleoid. The genetic material is referred to as genophore. Genophore is the bacterial chromosome. It has a double stranded circular supercoiled, DNA. DNA has about 10,000 genes in E.coli. Double stranded DNA in bacteria is without histones.

8. Transduction in bacteria is mediated by

(a) plasmid vectors

(b) phage vectors

(c) cosmids

(d) F-factors.

Answer and Explanation:

8. (b): Transduction involves transfer of, genetic material of one bacterial cell goes to other bacterial cell by agency of bacteriophages or phages (viruses, infecting bacteria).

Transduction was first of all reported in Salmonella typhineurium by Zinder and Lederberg.

9. Organisms, which fix atmospheric nitrogen in the soil, fall under the category of

(a) bacteria

(b) green algae

(c) soil fungi

(d) mosses.

Answer and Explanation:

9. (a): A few free living bacteria are able to pick up dinitrogen from the soil atmosphere and’convert it into organic nitrogenous materials like amino acids, e.g. Azotobacter. Symbiotic nitrogen fixing bacteria of the genus Rhizobium occur in the root nodules of a number of legumes. Root nodules containing symbiotic nitrogen bacteria also occur in Casuarina and Alnus. Leaf nodules containing such bacteria are found in Ardisia. Many cyanobacteria (blue-green algae) fix atmospheric nitrogen due to presence of heterocysts.

10. A large number of organic compounds can be decomposed by

(a) Azotobacter

(b) chemolithotrophs

(c) Mycoplasma

(d) Pseudomonas.

Answer and Explanation:

10. (b): Chemolithotrophs can derive the energy required for growth from the oxidation of inorganic components.

11. Which type of DNA is found in bacteria?

(a) circular free DNA

(b) membrane bound DNA

(c) straight DNA

(d) helical DNA.

Answer and Explanation:

11. (a): Bacterial cells do not have nucleus. Nuclear material of bacteria lies free in the cell in the form of an irregular, thin fibrillar and circular single molecule of DNA called nucleoid or chromatin body. This DNA is sometimes attached at one or more points to a mesosome. Bacterial DNA is not associated with histone proteins and does not coil to form well defined chromosomes during multiplication. This is the basic characteristic of all prokaryotes and a bacterium is prokaryotic organism.

12. What are the sex organs provided in some bacteria?

(a) sex pili

(b) plasmid

(c) circular DNA

(d) gametes.

Answer and Explanation:

12. (a): Sex pili are minute and non-flagellar hairlike structures projecting from the wall of many gram negative bacteria and few Gram +ve ones. They are entirely composed of a protein called pilin. They are used as sex organs during conjugation, forms conjugation tube during conjugation. They confer the property of stickiness whereby bacteria tend to adhere to one another (clump formation). They are of two types-long conjugating pili and short attachment pili.

Naked circular DNA is the genetic material which is not enclosed by nuclear membrane non complexed with proteins. It is called nucleoid or genophore. Plasmids (Hayes and Lederberg, 1952) are additional or extrachromosomal small rings of DNA having a few useful but nonvital genes, e.g., for fertility factor, R- factors or resistance factor.

13. Azotobacter and Bacillus polymyxa are the examples of

(a) pathogenic bacteria

(b) decomposers

(c) symbiotic N2 fixer

(d) non-symbiotic N2 fixer.

Answer and Explanation:

13. (d): Symbiosis is a mutually beneficial relationship or interaction between individuals of two different species with none of the two capable of living separately. e.g., Rhizobium is associated with root nodules of legumes. It fixes nitrogen for the plant and the plant provides it food and shelter. Azotobacter is a free-living bacteria which occurs in the soil and fixes nitrogen directly. Bacillus is also free living bacteria which acts upon nitrogenous excretions and proteins of dead bodies of living organisms. These are therefore, non-symbiotic N2 fixing bacteria.

14. Genes are packaged into a bacterial chromosome by

(a) acidic protein

(b) actin

(c) histones

(d) basic protein.

Answer and Explanation:

14. (d): In bacteria, DNA is highly charged molecule. The adjacent bases are linked by phosphate groups, each with an ionized hydroxyl group. It results in negative charges which are therefore balanced by an equivalent number of cationic groups.

These charges are balanced by histones which are basic proteins in case of eukaryotes. Histones are absent in bacterial cells. In bacteria the charges are neutralized by polyamines such as spermine and spermidine and by Mg2+ ions.

15. The hereditary material present in the bacterium E.coli is

(a) single-stranded DNA

(b) double-stranded DNA

(c) DNA

(d) RNA.

Answer and Explanation:

15. (b): E. coli is a gram-negative, rod shaped, motile or nonmotile bacteria. E. coli contains a double stranded DNA as its genetic material. The DNA is not associated with any histone proteins so it is referred to as naked DNA. This DNA is circular with no free ends.

16. The site of respiration in bacteria is

(a) ribosome

(b) microsome

(c) episome

(d) mesosome.

Answer and Explanation:

16. (d): Mesosomes are complex, intracellular, membranous structures within the cytoplasm, that are formed by the infoldings of the cytoplasmic membrane. Surface of mesosomes have many enzymes which take part in respiration e.g., oxidases and dehydrogenases. Mesosomes are also known to help in the separation of two daughter molecules of DNA during cell division. They are also called mitochondria of bacterial cell. Ribosomes are cytoplasmic organelles that occur in both prokaryotes and eukaryotes. When plasmids associate temporarily with nucleoid these are called as episomes.

17. Which of the following is free-living aerobic non- photosynthetic nitrogen-fixing bacterium?

(a) Nostoc

(b) Azospirillum

(c) Rhizobium

(d) Azotobacter.

Answer and Explanation:

17. (d): All plants need nitrogen to synthesize proteins, but for this purpose they are unable to utilize atmospheric nitrogen. Nitrogen fixation is brought about by two types of bacteria which are known as nitrogen fixing bacteria. One type is symbiotic nitrogen fixers that are associated with plants e.g., Rhizobium and Azospirillum.

The other types of these bacteria are free living in the soil e.g., Azotobacter and Nostoc.

Nostoc is photosynthetic and Azotobacter is non- photosynthetic.

So that, the free living aerobic non-photosynthetic nitrogen fixing bacterium is Azotobacter.

18. A few organisms are known to grow and multiply at temperatures of 100-105°C. They belong to

(a) thermophilic sulphur bacteria

(b) hot spring blue-green algae

(c) methanogenic archaebacteria

(d) marine archaebacteria.

Answer and Explanation:

18. (a): Thermoacidophiles (temperature and acid loving) archaebacteria are found in hot sulphur springs. Although they are microscopic, single-celled organisms, they flourish under conditions which would kill higher organisms. These are aerobic bacteria and have the capacity to oxidize sulphur to H2S04 at high temperature and high acidity (pH = 2.0). Some of them are also able to reduce sulphur to H2S under anaerobic conditions. As a rule, they grow best between 80° and 100°C and several species do not grow below 80°C.

19. The main role of bacteria in the carbon cycle involves

(a) chemosynthesis

(b) digestion or breakdown of organic compounds

(c) photosynthesis

(d) assimilation of nitrogenous compounds.

Answer and Explanation:

19. (b): Bacteria are responsible for maintaining the conditions of life as the earth by virtue of their powers of decomposition of plant and animal bodies by which the limited supply by CO2 available for photosynthesis is replenished. Thus, they act as decomposers in the carbon cycle. Bacteria mainly function as decomposers in the carbon cycle.

20. The DNA of E.coli is

(a) double stranded and linear

(b) double stranded and circular

(c) single stranded and linear

(d) single stranded and circular.


(b) double stranded and circular

21. A bacterium divides every 3 5 minutes. If a culture containing 10s cells per ml is grown for 175 minutes, what will be the cell concentration per ml after 175 minutes?

(a) 35 x io5 cells

(b) 32 x 105 cells

(c) 175 x io5 cells

(d) 85 x 105 cells.


(b) 32 x 105 cells

22. Transfer of genetic information from one bacterium to another in the transduction process is through

(a) bacteriophages released from the donor bacterial strain

(b) another bacterium having special organ for conjugation

(c) physical contact between donor and recipient strains

(d) conjugation between opposite strain bacterium.

Answer and Explanation:

22. (a): Transduction is the phenomenon of transfer of genetic material from one bacterial cell to another through the agency of virus. The viruses carry a segment of DNA from one host and infect another host which is different from the first one, the latter may inherit some of the properties of the former host due to transfer of DNA segment through infecting phage.

23. Photosynthetic bacteria have pigments in

(a) chromoplasts

(b) chromatophore

(c) leucoplasts

(d) chloroplasts.

Answer and Explanation:

23. (b): Photosynthetic bacteria have chromatophores which are membrane bound vesicular structures which are extensions of cytoplasmic membrane. They contain photosynthetic pigments along with enzymes and electron carriers for photosynthetic phosphorylation. These pigments are bacteriochlorophyll and bacteriop- haeophytin. Leucoplasts, chloroplasts and chromoplasts are different types of plasids which occur in plastids and some protistans.

24. Difference in gram positive and gram negative bacteria is due to

(a) cell wall

(b) cell membrane

(c) ribosome

(d) cytoplasm.

Answer and Explanation:

24. (a): Using Gram stain, developed by Danish physician, Christian Gram in 1884, two kinds of bacteria were noted – those species of bacteria that are decolorized by alcohol are called gram negative and those that retain the stain are called gram positive. This property of bacteria is related with the structure and compositional differences between the walls of gram positive and gram negative forms.

In the cell wall of Gram +ve bacteria, both horizontal and vertical peptide linkages are present, due to which mesh is dense and hence the stain doesn’t come out. Further outer layer of cell wall of Gram +ve bacteria is made of teichoic acid.

In the cell wall of Gram -ve bacteria, either horizontal or vertical peptide linkage are present, due to which mesh is loose and hence stain comes out. Further outermost layer of cell wall of Gram -ve bacteria is made of lipopolysaccharides.

25. What is true for archaebacteria?

(a) all halophils

(b) all photosynthetics

(c) all fossils

(d) oldest living beings.

Answer and Explanation:

25. (d): Archaebacteria are believed to have originated at a time when there were extreme conditions in the biosphere. Even today they are found in environments where other kinds of bacteria cannot survive. So they are considered to be the oldest of the living fossils.

Eg. Methanobacterinm, Methonococcus etc. All of them are not halophiles. Only some forms like Halobacterium, Halococcus can survive under extreme saline conditions. All of them are not fossils because many forms are still surviving and flourishing.

26. What is true for cyanobacteria?

(a) oxygenic with nitrogenase

(b) oxygenic without nitrogenase

(c) non oxygenic with nitrogenase

(d) non oxygenic without nitrogenase.

Answer and Explanation:

26. (a): Cyanobacteria are gram negative prokaryotes which are popularly known as blue-green algae. Although cyanobacteria are true prokaryotes, but their photosynthetic system closely resembles with that of eukaryotes because they have chlorophyll a and photosystem II and they carry out oxygenic photosynthesis.

Like the red algae, cyanobacteria use phycobiliproteins as accessory pigments. Photosynthetic pigments and electron transport chain components are located in thylakoid membranes lined with particles called phycobilisomes, which contain phycobilin pigments, particularly phycocyanin and transfer energy to photosystem II.

They contain nitrogenase enzyme for nitrogen fixation. This enzyme becomes inactive in the presence of oxygen but the thick walled heterocysts provide suitable anaerobic enviornment for nitrogenase activity even in aerobic conditions.

27. Choose the correct sequence of stages of growth curve for bacteria:

(a) lag, log, stationary, decline phase

(b) lag, log, decline, stationary phase

(c) stationary, lag, log, decline phase

(d) decline, lag, log phase, stationary.


(a) lag, log, stationary, decline phase

28. In bacteria, plasmid is

(a) extra chromosomal material

(b) main DNA

(c) non functional DNA

(d) repetitive gene.

Answer and Explanation:

28. (a): In addition to the nucleoid, bacterial cytoplasm normally contains many small, separate pieces of DNA, called plasmids. These circular DNA units are 1/100 the size of the main nuclear DNA (nucleoid) and are also not enclosed in a membrane structure. When found in cytoplasm, entirely independent of the bacterial chromosome, they replicate autonomously.

Sometimes it becomes integrated into the main DNA and replicates with it. During conjugation, the plasmids, sometimes called episomes, help in the transfer of the genetic material between different bacteria. It may carry some genes of resistance to a variety of antibiotics.

29. Some bacteria able to grow in Streptomycin containing medium due to

(a) natural selection

(b) induced mutation

(c) reproductive isolation

(d) genetic drift.

Answer and Explanation:

29. (a): Normally bacteria cannot survive in antibiotic containing medium but if it does so it must have acquired resistance against that antibiotic. These are well adapted to grow in streptomycin containing medium and thus are more evolved. So due to natural selection only the more evolved and better adapted species is able to survive.

30. The growth curve of bacterial population in lab is plotted against time. What will be the shape of graph?

(a) sigmoid

(b) hyperbolic

(c) ascending straight line

(d) descending straight line.


(b) hyperbolic

31. Which statement is correct for bacterial transduction?

(a) transfer of some genes from one bacteria to another bacteria through virus

(b) transfer of genes from one bacteria to another bacteria by conjugation

(c) bacteria obtained its DNA directly from mother cell

(d) bacteria obtained DNA from other external source.

Answer and Explanation:

31. (a): In transduction, genetic material of one bacterial cell goes to other bacterial cell by agency of bacteriophages or phages (viruses, infecting bacteria). Transduction was first of all reported in Salmonella typhineurium by Zinder and Lederberg (1952).

Transduction is used for gene mapping and analysis in bacteria and also for strain construction.

32. Chromosomes in a bacterial cell can be 1 – 3 in number and

(a) are always circular

(b) are always linear

(c) can be either circular or linear, but never both within the same cell

(d) can be circular as well as linear within the same cell

Answer and Explanation:

32. (a): Bacterial cells do not have nucleus, characteristic of eukaryotic cells. Nuclear material of bacteria lies free in the cell in the form of an irregular, thin, fibrillar and circular single molecule of DNA, called nucleoid or chromatin body.

This DNA, sometimes attached at one or more points to a mesosome, frequently runs parallel to the axis of the cell, Bacteria! DNA is not associated with histone protein and does not coil to form well-defined chromosomes during the multiplication. In addition to circular DNA, a small amount of subsidiary extrachromosomal DNA is also present as plasmids or episomes.

33. During replication of a bacterial chromosome DNA synthesis starts from a replication origin site and

(a) RNA primers are involved

(b) is facilitated by telomerase

(c) moves in one direction of the site

(d) moves in bi-directional way.

Answer and Explanation:

33. (d): Anabaena is a free living nitrogen fixing cyanobacterium which can form symbiotic association with the water fern Azolla.

34. A free living nitrogen-fixing cyanobacterium which can also form symbiotic association with the water fern Azolla is

(a) Tolypothrix

(b) Chlorella

(c) Nostoc

(d) Anabaena.

Answer and Explanation:

34. (d): Prokaryotic DNA acts as a single replicating unit called replicon. Each replicon has a particular region where replication starts. It is called origin of replication or ori. In the region of ori, there is a particular nucleotide sequence called autonomic replicating sequence or ARS. Replication proceeds bidirectionally from each ori. A replication fork is produced on each side of ori. Replication will continue till a replication fork meets another replication fork.

35. Basophilic prokaryotes

(a) grow and multiply in very deep marine sediments

(b) occur in water containing high concentrations of barium hydroxide

(c) readily grow and divide in sea water enriched in any soluble salt of barium

(d) grow slowly in highly alkaline frozen lakes at high altitudes.

Answer and Explanation:

35. (a): Basopilic prokaryotes are facultatively anaerobic bacteria. They grow and multiply in very deep marine sediments. Most basophiles grow better at a pH of 8.5 or higher.

36. For retting of jute the fermenting microbe used is

(a) methanophilic bacteria

(b) butyric acid bacteria

(c) Helicobactor pylori

(d) Streptococcus lactin.

Answer and Explanation:

36. (b): Retting is the process of separating fibres that are held together in close association using a variety of bacteria. Fibers ofjute are held together in close association and they are separated by the action of butyric acid bacteria e.g. Clostridium butyricum.

These plants are immersed in water so that they absorb water and swell. Due to the activity of bacteria, the pectic substances of middle lamella are hydrolysed and the fibers are separated. These separated fibers are used in making of ropes and sacks.

37. All of the following statements concerning the actinomycetous filamentous soil bacterium Frankia are correct except that Frankia

(a) can induce root nodules on many plant species

(b) can fix nitrogen in the free-living state

(c) cannot fix specialized vesicles in which the nitrogenase is protected from oxygen by a chemical barrier involving triterpene hopanoids

(d) like Rhizobium, it usually infects its host plant through root hair deformation and stimulates cell proliferation in the host’s cortex.

Answer and Explanation:

37. (b): Frankia, is a nitrogen fixing symbiotic bacteria. It induces root nodules just like Rhizobium. It is associated symbioticaliy with the root nodules of several non-legume plants like Casuarina, Alnus, and Rubtis etc. It cannot fix nitrogen in Free State.

38. Curing of tea leaves is brought about by the activity of

(a) fungi

(b) bacteria

(c) mycorrhiza

(d) viruses

Answer and Explanation:

38. (b): Curing is a process done to add special flavour and taste in tea leaves. It is also done for tobacco. In this process after harvesting the cured leaves are hung in shade and are permitted for the action of bacteria. The curing of tea leaves is done by Mycrococcus candidans. Mycrococcus is a gram positive aerobic bacterium which is a member of micrococcaceae.

39. Which one of the following statements about mycoplasma is wrong?

(a) they are pleomorphic

(b) they are sensitive to penicillin

(c) they cause diseases in plants

(d) they are also called PPLO.

Answer and Explanation:

39. (b): Mycoplasma are small, unicellular, (non- motile) prokaryotic organisms. They are pleomorphic. Therefore they are known as pleuro pneumonia like organisms (PPLO). They lack cell wall. It contains cytoplasm, ribosomes and DNA. They are inhibited by tetracyclines but insensitive to penicillin. They cause various diseases.

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