Monera (Prokaryotes) Questions in English

(C) The highly resistant nature of an endospore is primarily attributed to the presence of dipicolinic acid and calcium ions $(Ca^{2+})$ in the cortex layer of the spore.
These components contribute to the heat resistance,chemical resistance,and overall stability of the endospore,allowing it to survive in harsh environmental conditions.

(B) Endospores are highly resistant,dormant structures produced by certain bacteria such as $Bacillus$ and $Clostridium$ species.
They are not a method of reproduction because they do not increase the number of individuals.
Instead,they serve as a means of perennation,allowing the bacteria to survive under extremely harsh environmental conditions like high temperature,radiation,desiccation,and chemical disinfectants.

(B) $F^{+}$ bacteria contain the $F$ plasmid (fertility factor).
They are considered donor bacteria because they can transfer genetic material to $F^{-}$ recipient cells.
They cannot conjugate with another $F^{+}$ cell because the presence of the $F$ plasmid prevents the formation of a conjugation bridge between two donor cells.
$F^{+}$ bacteria possess both fertility pili (sex pili) and somatic pili,not just somatic pili. Therefore,the statement that 'only somatic pili are present' is incorrect.

(A) $MLOs$ (Mycoplasma-like organisms) are members of the kingdom $Monera$. They lack a cell wall,which makes them pleomorphic (variable in shape) and non-motile.
Since they lack a cell wall,they are not affected by antibiotics like penicillin,which specifically target cell wall synthesis in bacteria.
Therefore,both the Assertion $(A)$ and the Reason $(R)$ are correct,and the Reason correctly explains why $MLOs$ are insensitive to penicillin.

(D) The Assertion is incorrect because the majority of bacteria are heterotrophs,not autotrophs. They depend on other organisms or on dead organic matter for food.
The Reason is also incorrect because chemoheterotrophic nutrition is,in fact,the most common mode of nutrition in bacteria. Many bacteria are saprophytes or parasites that obtain energy and carbon from organic compounds.
Therefore,both the Assertion and the Reason are incorrect.

(B) In some prokaryotes like cyanobacteria or blue-green algae,there are specialized membranous extensions in the cytoplasm that contain pigments,which are called chromatophores.
These structures are involved in photosynthesis.

(D) Gas vacuoles,also known as pseudovacuoles,are specialized structures found in certain prokaryotic organisms.
These structures provide buoyancy to the cells,allowing them to float at specific depths in aquatic environments.
Gas vacuoles are characteristically present in Blue-green algae (cyanobacteria),as well as green and purple photosynthetic bacteria.
Since both option $A$ and option $B$ are correct,the most appropriate choice is $D$.

(B) Peptidoglycan, also known as murein, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of most bacteria, forming the cell wall.
It is a heteropolymer (specifically a heteropolysaccharide) because it is composed of two alternating amino sugar molecules, $N$-acetylglucosamine $(NAG)$ and $N$-acetylmuramic acid $(NAM)$, which are linked by $\beta-(1,4)$ glycosidic bonds and cross-linked by short peptide chains.

(D) Cyanobacteria,also known as blue-green algae $(BGA)$,possess the unique ability to fix atmospheric nitrogen.
This process is facilitated by specialized,thick-walled cells known as heterocysts.
These cells provide an anaerobic environment necessary for the activity of the enzyme nitrogenase,which is sensitive to oxygen.

(A) $Azotobacter$ is a free-living,aerobic,and saprotrophic nitrogen-fixing bacterium.
It lives in the soil and fixes atmospheric nitrogen independently without forming a symbiotic relationship with plants.

(D) Obligate anaerobes are organisms that cannot use oxygen for growth and are often killed or harmed by its presence.
They lack the enzymes (such as superoxide dismutase and catalase) required to detoxify the reactive oxygen species produced in the presence of $O_2$.
Therefore,they grow only in environments completely devoid of oxygen.

(C) Bacteria do not undergo true sexual reproduction as they lack meiosis and gamete formation. However,they exhibit genetic recombination,which is a process equivalent to sexual reproduction.
Conjugation is the primary mechanism of genetic recombination in bacteria,where genetic material (usually a plasmid) is transferred from a donor bacterium to a recipient bacterium through a direct physical contact via a pilus.
Therefore,conjugation is considered the mode equivalent to sexual reproduction in bacteria.

(A) Cyanobacteria,also known as blue-green algae,are prokaryotic organisms.
They are primarily unicellular,colonial,or filamentous,but they are not multicellular in the true sense of having differentiated tissues or organs.
They are known for forming colonies and often produce blooms in polluted water bodies due to nutrient enrichment (eutrophication).
Many species of cyanobacteria,such as $Anabaena$ and $Nostoc$,possess specialized cells called heterocysts that allow them to fix atmospheric nitrogen.
Therefore,the statement that they are multicellular is not a characteristic feature of cyanobacteria.

(D) Bacteria possess a single circular $ds-DNA$ molecule which acts as the main chromosomal $DNA$ and is located in the nucleoid region.
Additionally,many bacteria contain small,circular,extrachromosomal $DNA$ molecules known as plasmids.
Therefore,$DNA$ in bacteria can be both chromosomal (nucleoid) and extrachromosomal (plasmid).

(D) Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments.
Many of these cyanobacteria,such as $Anabaena$,$Nostoc$,and $Oscillatoria$,are capable of fixing atmospheric nitrogen.
They contribute to soil fertility by increasing the organic matter content through their photosynthetic activity and nitrogen fixation.
Therefore,all three mentioned organisms are capable of nitrogen fixation.

(D) An organism (such as a bacterium) that can grow on a minimal medium without needing any specific nutritional supplements is called a $Prototroph$.
In contrast,an $Auxotroph$ is a mutant organism that cannot synthesize a particular compound required for its growth and therefore requires the addition of that specific nutrient (such as an amino acid or vitamin) to the growth medium.

(C) Archaebacteria are the organisms found in extreme environments like boiling thermal springs and deep-sea hydrothermal vents.
This is due to the unique structure of their cell wall and cell membrane,which contains branched-chain lipids that provide stability and resistance to extreme heat and acidic conditions.

(N/A) Mycoplasma are organisms that completely lack a cell wall.
$\rightarrow$ They are the smallest living cells known and can survive without oxygen.
$\rightarrow$ Many mycoplasma are pathogenic in animals and plants.
$\rightarrow$ Mycoplasma are the simplest free-living prokaryotes.
$\rightarrow$ They are also known as $PPLO$ (Pleuropneumonia-like organisms).

(N/A)

Eubacteria	Archaebacteria
$(1)$ Cell wall is made up of peptidoglycan.	$(1)$ Peptidoglycan is absent in the cell wall; it is composed of complex polysaccharides and proteins.
$(2)$ Plasma membrane consists of straight-chain fatty acids linked by ester bonds.	$(2)$ Plasma membrane consists of branched-chain lipids linked by ether bonds.
$(3)$ Genes are generally not interrupted by non-coding sequences (introns).	$(3)$ Genes are often interrupted by introns,similar to eukaryotes.
$(4)$ Ribosomal proteins and $RNA$ polymerase enzymes are distinct from those of eukaryotes.	$(4)$ Ribosomal proteins and $RNA$ polymerase are structurally similar to those of eukaryotes.

(N/A)

Bacteria	Cyanobacteria
$(1)$ Cells are smaller.	$(1)$ Cells are comparatively larger.
$(2)$ Cell wall is $1-2$ layered.	$(2)$ Cell wall is four-layered.
$(3)$ They may possess flagella.	$(3)$ They lack flagella.
$(4)$ They are autotrophic and heterotrophic.	$(4)$ They are primarily autotrophic.
$(5)$ Autotrophic bacteria contain bacteriochlorophyll.	$(5)$ They possess chlorophyll-$a$ as found in eukaryotic autotrophs.
$(6)$ Photosynthesis is anoxygenic.	$(6)$ Photosynthesis is oxygenic.
$(7)$ They may be aerobic or anaerobic.	$(7)$ They are aerobic.
$(8)$ The reserve food is glycogen.	$(8)$ The reserve food is cyanophycean starch.

(N/A) $(1)$ $MLO$ stands for Mycoplasma-Like Organisms. These are small,wall-less prokaryotes that are often pathogenic to plants.
$(2)$ $VAM$ stands for Vesicular-Arbuscular Mycorrhizae. These are a type of endomycorrhiza in which fungi form vesicles and arbuscules within the root cells of plants to facilitate nutrient uptake.

(D) Cyanobacteria are significant for several reasons:
$1$. Nitrogen Fixation: Many cyanobacteria,such as $Anabaena$ and $Nostoc$,possess specialized cells called heterocysts that fix atmospheric nitrogen into ammonia,enriching soil fertility.
$2$. Environmental Conservation: They help in the prevention of soil erosion and contribute to soil conservation by forming crusts on the soil surface.
$3$. Nutritional Value: Species like $Spirulina$ are widely used as protein-rich dietary supplements for humans due to their high nutritional content.

(B) The term $Bacteria$ was proposed by the scientist Christian Gottfried Ehrenberg in $1829$.

(B) Anton Von Leeuwenhoek is credited with the discovery of bacteria. He observed these microorganisms for the first time in $1675$ using a simple microscope he designed himself.

(N/A) $\rightarrow$ Some cyanobacteria or blue-green algae like $Nostoc$ and $Oscillatoria$ can tolerate adverse conditions,including pollutants,much better than other aquatic plants.
This is due to the presence of a protective mucilage covering,resistant proteins,and the absence of sap vacuoles.
They release a large quantity of spores that are always present in the air.
These organisms obtain plenty of nutrients in polluted water,which promotes their rapid growth.
Hence,they often bloom in such conditions and are found in abundance in polluted water.

(A) Chemosynthetic bacteria are autotrophic because they can synthesize their own food.
During chemosynthesis,they use inorganic chemicals as a source of energy to fix carbon dioxide into organic compounds.

(A) $1$. According to the "five kingdom classification" proposed by $R$.$H$. Whittaker, all prokaryotic organisms are placed under the kingdom Monera.
$2$. Both cyanobacteria and heterotrophic bacteria are prokaryotic in nature, meaning they lack a membrane-bound nucleus and other membrane-bound organelles.
$3$. The classification is justified because the primary criterion for placing organisms in kingdom Monera is their prokaryotic cellular organization.
$4$. Cyanobacteria (blue-green algae) are photosynthetic autotrophs containing chlorophyll-$a$, while heterotrophic bacteria obtain nutrients from organic matter. Despite this difference in the mode of nutrition, their fundamental cellular structure (prokaryotic) remains the same, which is the defining characteristic of eubacteria.

(B) Statement $I$ is correct: Mycoplasma are the smallest known living cells,typically ranging from $0.1 \ \mu m$ to $0.3 \ \mu m$ in size. Due to their extremely small size,they can easily pass through bacterial-proof filters (which usually have a pore size of $1 \ \mu m$ or less).
Statement $II$ is incorrect: Mycoplasma are unique among bacteria because they completely lack a cell wall. This absence of a cell wall makes them naturally resistant to antibiotics like penicillin that target cell wall synthesis.
Therefore,Statement $I$ is correct and Statement $II$ is incorrect.

(D) Option $A$ is incorrect because bacteria can be autotrophic (photosynthetic or chemosynthetic) or heterotrophic.
Option $B$ is incorrect because slime moulds are protists,not members of Kingdom $Monera$.
Option $C$ is incorrect because $Mycoplasma$ lack a cell wall.
Option $D$ is correct because $Cyanobacteria$ (blue-green algae) are photosynthetic autotrophs and are classified under Kingdom $Monera$ as prokaryotes.

(A) Prokaryotic organisms belong to the Kingdom $Monera$.
$1$. Bacteria: These are prokaryotic organisms.
$2$. Blue-green algae (Cyanobacteria): These are also prokaryotic organisms.
All other organisms listed (Fungi,Porifera,Echinodermata,Moss,Bryophytes,Pteridophytes,Gymnosperms,Ctenophora,and Angiosperms) are eukaryotic organisms.
Therefore,there are only $2$ prokaryotic organisms in the given list.
Thus,the correct option is $A$.

(A) The kingdom $Monera$ is the only kingdom in the five-kingdom classification system that consists of unicellular prokaryotic organisms. These organisms lack a defined nucleus and membrane-bound organelles. Examples include bacteria and cyanobacteria.

(A) Bacteria are grouped into $4$ categories based on their shape:
$1$. Spherical (Coccus)
$2$. Rod-shaped (Bacillus)
$3$. Comma-shaped (Vibrio)
$4$. Spiral (Spirillum)

(D) Based on the morphological shapes of bacteria shown in the figure:
$1$. The first group shows spherical-shaped bacteria,which are known as $Coccus$.
$2$. The second group shows rod-shaped bacteria,which are known as $Bacillus$.
$3$. The third group shows spiral-shaped bacteria,which are known as $Spirillum$.
$4$. The fourth group shows comma-shaped bacteria,which are known as $Vibrio$.
Therefore,the correct sequence is $Coccus$,$Bacillus$,$Spirillum$,$Vibrio$.

(A) According to the $NCERT$ textbook,bacteria are characterized by a very simple structure but complex behavior. Therefore,the statement that 'Bacteria have a simple structure despite their complex behavior' is correct. Bacteria show the most extensive metabolic diversity among all organisms. Most bacteria are heterotrophic (they do not synthesize their own food but depend on other organisms or on dead organic matter for food). Autotrophic bacteria synthesize their own food from inorganic substrates. Thus,all given options are factually correct based on biological principles. However,if the question asks for an 'incorrect' option and all are correct,it implies a potential error in the question framing. Given the standard $NCERT$ text,all these statements are true.

(D) Bacteria are classified based on their mode of nutrition into two main categories: Autotrophic and Heterotrophic.
$1$. Autotrophic bacteria $(P)$ can synthesize their own food. They are further divided into photosynthetic (using light energy) and chemosynthetic (using chemical energy) bacteria.
$2$. Heterotrophic bacteria $(Q)$ cannot synthesize their own food and depend on other organisms. They include parasitic (living on or in other organisms) and saprophytic (decomposing dead organic matter) bacteria.
Therefore,$P$ includes photosynthetic and chemosynthetic bacteria,while $Q$ includes parasitic and saprophytic bacteria. The correct option is $D$.

(A) Archaebacteria are unique because they live in some of the most harsh habitats such as extreme salty areas (halophiles),hot springs (thermoacidophiles),and marshy areas (methanogens).
Their cell wall structure is responsible for their survival in these extreme conditions,which is different from other bacteria.

(B) Archaebacteria are special because they live in some of the most harsh habitats.
$1$. Halophiles $(P)$ are found in extremely salty areas.
$2$. Methanogens $(Q)$ are found in marshy areas.
$3$. Thermoacidophiles $(R)$ are found in hot springs.
Therefore, the correct matching is $P-III, Q-II, R-I$.

(B) $Methanogens$ are a group of $Archaebacteria$ that are strictly anaerobic. They are found in the gut of several ruminant animals such as cows and buffaloes. These bacteria are responsible for the production of methane (biogas) from the dung of these animals.

(B) The provided figure shows a filamentous cyanobacterium (blue-green alga) known as $Nostoc$.
In the diagram,$P$ represents the $Heterocyst$,which is a specialized cell responsible for nitrogen fixation.
$Q$ represents the $Mucilaginous$ $sheath$ that surrounds the colony of cells.
Therefore,the correct identification is $Nostoc$ with $P$ as $Heterocyst$ and $Q$ as $Mucilaginous$ $sheath$.

(A) Cyanobacteria,also known as blue-green algae,are photosynthetic prokaryotes that contain chlorophyll $a$ and perform oxygenic photosynthesis.
Rhizobium is a nitrogen-fixing bacterium found in root nodules of leguminous plants.
Mycoplasma is a genus of bacteria that lack a cell wall and are generally parasitic or saprophytic.
Lactobacillus is a lactic acid bacterium involved in the fermentation of milk into curd.
Therefore,the correct answer is Cyanobacteria.

(A) Heterocysts are specialized,thick-walled cells found in certain filamentous cyanobacteria like $Nostoc$ and $Anabaena$.
Their primary function is the fixation of atmospheric nitrogen $(N_2)$ into ammonia,which is essential for the organism's growth.
They provide an anaerobic environment necessary for the activity of the enzyme nitrogenase,which is sensitive to oxygen.

(D) Chemoautotrophs are organisms that synthesize their own food by utilizing the chemical energy released from the oxidation of inorganic substances (such as nitrates,nitrites,or ammonia).
$1$. They are autotrophs because they synthesize their own food.
$2$. They oxidize inorganic substances to obtain energy.
$3$. The energy released during this oxidation process is used for the production of $ATP$.
Therefore,all the given options are correct.

(C) The incorrect statement is $C$.
$Mycoplasma$ are known as the smallest living cells.
$Mycoplasma$ are organisms that lack a cell wall and can survive without oxygen.
They are not part of Eubacteria but are distinct organisms within the Kingdom Monera.
All other statements are correct: Eubacteria are prokaryotic,autotrophic bacteria are abundant in nature,and blue-green algae $(Cyanobacteria)$ are classified under Eubacteria.

(D) $Eubacteria$ (true bacteria) are extremely diverse in nature.
$1.$ They are helpful in making curd from milk (e.g.,$Lactobacillus$),production of antibiotics,and nitrogen fixation in legume roots (e.g.,$Rhizobium$).
$2.$ Many bacteria are pathogenic and cause damage to human beings,crops,farm animals,and pets.
$3.$ Diseases such as cholera,typhoid,tetanus,and citrus canker are caused by different bacteria.
Therefore,all the given statements are correct.

(B) Conjugation is a process in bacteria where genetic material,typically a plasmid (such as the $F$-plasmid),is transferred from a donor bacterium to a recipient bacterium.
In this process,specialized structures called 'pili' or 'sex pili' play a crucial role in establishing contact between the cells.
Fimbriae,on the other hand,are primarily involved in the attachment of bacteria to surfaces or host tissues,not in the conjugation process.
Furthermore,while conjugation involves the transfer of genetic material,it is not considered true sexual reproduction because it does not involve meiosis or the formation of gametes.
Therefore,both statement $B$ and statement $C$ are technically incorrect,but since the question asks for the incorrect statement and $B$ is a specific structural error regarding the mechanism,$B$ is the most direct incorrect statement provided.

(D) $Mycoplasma$ are organisms that completely lack a cell wall.
They are the smallest living cells known and can survive without oxygen.
$Mycoplasma$ are pathogenic to both plants and animals.
Therefore,the statement that they cause diseases only in animals is incorrect.

(D) Prokaryotic cells are characterized by the absence of a well-defined nucleus and membrane-bound organelles. According to the five-kingdom classification system proposed by $R$.$H$. Whittaker,all prokaryotic organisms are placed under the kingdom $Monera$. Kingdoms $Plantae$,$Protista$,and $Fungi$ consist of eukaryotic organisms.

(B) Bacteria are classified into two groups based on the differences in their cell envelopes and the manner in which they respond to the staining procedure developed by Christian Gram.
$1$. Bacteria that take up and retain the Gram stain (crystal violet) are known as Gram-positive bacteria.
$2$. Bacteria that do not retain the Gram stain are known as Gram-negative bacteria.

(C) Cyanobacteria are photosynthetic prokaryotes. They contain membrane-bound extensions in their cytoplasm that contain pigments,which are known as $Chromatophores$. These structures are involved in photosynthesis. Chloroplasts and mitochondria are membrane-bound organelles found only in eukaryotic cells,and chromoplasts are a type of plastid found in plants.

(C) Fimbriae are small,bristle-like fibers sprouting out of the cell in many bacteria. Their primary function is to help the bacteria attach to rocks in streams and also to the host tissues. Conjugation is primarily mediated by pili,not fimbriae. Locomotion in bacteria is primarily mediated by flagella. Therefore,the removal of fimbriae specifically prevents the bacteria from attaching to the substrate.