Monera (Prokaryotes) Questions in English

(B) Heterocysts are specialized,thick-walled cells found in certain filamentous cyanobacteria such as $Nostoc$ and $Anabaena$.
These cells are specialized for the process of nitrogen fixation because they provide an anaerobic environment necessary for the enzyme nitrogenase to function,as it is sensitive to oxygen.
$Methanogens$ are Archaebacteria,$Gonyaulax$ is a dinoflagellate (Protista),and $Euglena$ is a flagellated protozoan (Protista).
Therefore,the correct option is $B$.

(C) Thermoacidophiles belong to the domain $Archaea$.
They are a group of extremophilic microorganisms that thrive in extremely hot and acidic environments,such as hot springs and volcanic vents.
Unlike typical bacteria,their cell walls lack peptidoglycan,and their membrane lipids contain branched-chain hydrocarbons,which are characteristic features of $Archaebacteria$.

(B) Cyanobacteria,also known as blue-green algae,are photosynthetic prokaryotes.
They contain chlorophyll $a$,similar to green plants,which allows them to perform oxygenic photosynthesis.
Since they can synthesize their own food using light energy,they are classified as autotrophic organisms.
They belong to the Kingdom $Monera$.

(A) In the kingdom $Monera$ (bacteria), reproduction primarily occurs through asexual means.
Under favorable (normal) conditions, bacteria reproduce rapidly by $binary \text{ } fission$, where a single cell divides into two daughter cells.
Under unfavorable (adverse) conditions, bacteria produce spores (such as $endospores$) to survive the harsh environment until conditions become favorable again.
Therefore, the correct sequence is spore formation for adverse conditions and binary fission for normal conditions.

(B) Eubacteria are known as 'true bacteria'.
$(2)$ Anabaena is a cyanobacterium (blue-green alga),which is a type of eubacteria.
$(3)$ Many cyanobacteria like Anabaena perform $N_2$ fixation.
$(7)$ Cyanobacteria possess a gelatinous sheath surrounding their colonies.
$(8)$ Heterocysts are specialized cells found in some filamentous cyanobacteria (like Anabaena) that are responsible for $N_2$ fixation.
Methanogens $(1)$ and Thermoacidophiles $(4)$ are Archaebacteria.
Diatoms $(6)$ are Protists (Eukaryotes).
Therefore,the correct association with eubacteria is $(2, 3, 7, 8)$.

(A) Option $A$ is correct. $Nostoc$ is a cyanobacterium (blue-green alga) that possesses specialized cells called heterocysts,which are responsible for nitrogen fixation.
Option $B$ is incorrect because Dinoflagellates are protists,not viruses.
Option $C$ is incorrect because $Paramoecium$ is a ciliated protozoan,not flagellated.
Option $D$ is incorrect because $Penicillium$ is a multicellular fungus,whereas yeast is an example of a unicellular fungus.

(B) $Nostoc$ is a genus of cyanobacteria (blue-green algae) that can fix atmospheric nitrogen.
These organisms possess specialized,thick-walled cells known as $Heterocysts$.
$Heterocysts$ provide an anaerobic environment necessary for the enzyme $Nitrogenase$ to function,which is responsible for the conversion of atmospheric nitrogen into ammonia.

(C) Kingdom Monera includes all prokaryotic organisms.
Bacteria are the sole members of the Kingdom Monera.
They are unicellular and prokaryotic,meaning they lack a membrane-bound nucleus and other organelles.
Unicellular eukaryotes are classified under Kingdom Protista,and multicellular eukaryotes are classified under Kingdoms Fungi,Plantae,and Animalia.
Therefore,the correct answer is Bacteria.

(A) Based on the shapes of bacteria,they are classified into four types:
$1$. Cocci: Spherical shaped bacteria (labeled as $S$ in the figure).
$2$. Bacilli: Rod-shaped bacteria,often with endospores (labeled as $P$ in the figure).
$3$. Spirilla: Spiral-shaped bacteria with flagella (labeled as $Q$ in the figure).
$4$. Vibrio: Comma-shaped bacteria (labeled as $R$ in the figure).
Therefore,the correct identification is $P$-Bacilli,$Q$-Spirilla,$R$-Vibrio,and $S$-Cocci.

(B) Methanogens are a group of archaebacteria that produce methane $(CH_4)$ as a metabolic byproduct in anoxic conditions.
They are commonly found in the gut of ruminant animals like cows and buffaloes,where they help in the digestion of cellulose.
Therefore,they are found in high concentrations in cattle yards due to the presence of animal dung,which provides an ideal anaerobic environment for their growth.

(B) Mycoplasma are organisms that completely lack a cell wall.
Because they lack a cell wall,they are naturally resistant to antibiotics like penicillin,which work by inhibiting cell wall synthesis.
They are the smallest living cells known and can survive without oxygen.
They are also known as $PPLO$ ($Pleuro-Pneumonia-Like$ $Organisms$).
They are pathogenic to both plants and animals.
Therefore,the statement that they are sensitive to penicillin is incorrect.

(D) $Eubacteria$ are prokaryotic organisms characterized by a rigid cell wall made of peptidoglycan.
Photosynthetic $Eubacteria$ (like Cyanobacteria) contain chlorophyll-$a$,similar to green plants.
Many bacteria possess a gelatinous envelope or slime layer outside the cell wall.
$A$ $Zygote$ is a diploid cell formed by the fusion of two haploid gametes,which is a characteristic feature of eukaryotic sexual reproduction.
$Eubacteria$ reproduce primarily by binary fission and do not undergo sexual reproduction involving gamete fusion to form a $Zygote$.

(D) Archaebacteria are considered the oldest living organisms because they possess a unique cell wall structure that allows them to survive in some of the most harsh habitats,such as extreme salty areas (halophiles),hot springs (thermoacidophiles),and marshy areas (methanogens).
These organisms are believed to have evolved very early in the history of life on Earth,hence they are often referred to as 'living fossils' or the oldest living beings.

(B) $PPLO$ stands for Pleuro Pneumonia-Like Organisms.
These are the smallest living cells known,which can survive without oxygen.
They are also known as Mycoplasma and lack a cell wall.

(D) Gas vacuoles (also known as gas vesicles) are specialized structures found in certain prokaryotes,including various bacteria and archaea.
These structures provide buoyancy,allowing the organisms to float at specific depths in aquatic environments to optimize light absorption for photosynthesis or to reach nutrient-rich layers.
Gas vacuoles are commonly present in photosynthetic prokaryotes such as $A$ (Blue-green bacteria or Cyanobacteria),$B$ (Green photosynthetic bacteria),and $C$ (Purple photosynthetic bacteria).
Therefore,the correct answer is $D$ (All of the above).

(A) $Cyanobacteria$ are photosynthetic prokaryotes.
They lack membrane-bound organelles such as a nucleus or chloroplasts.
Instead,they contain specialized pigment-containing structures called chromatophores,which are extensions of the plasma membrane that facilitate photosynthesis.
Therefore,they are prokaryotic cells that possess chromatophores.

(B) The kingdom $Monera$ consists of prokaryotic organisms, primarily bacteria.
$Escherichia$ (e.g., $Escherichia coli$) is a well-known bacterium belonging to the kingdom $Monera$.
$Amoeba$ is a protist (kingdom $Protista$).
$Gelidium$ is a red alga (kingdom $Protista$).
$Spirogyra$ is a green alga (kingdom $Plantae$).
Therefore, the correct option is $B$.

(A) The primary difference between Gram-positive and Gram-negative bacteria is the composition and structure of their cell wall.
Gram-positive bacteria possess a thick layer of peptidoglycan (murein) in their cell wall,which retains the crystal violet stain.
Gram-negative bacteria have a much thinner layer of peptidoglycan and an additional outer membrane containing lipopolysaccharides $(LPS)$,which prevents the retention of the crystal violet stain.

(D) Thermophilic blue-green algae (cyanobacteria) can survive in high-temperature environments due to the presence of specific structural adaptations in their proteins. These organisms possess proteins with a high proportion of homopolar bonds,which provide greater thermal stability and prevent denaturation at high temperatures. This allows them to maintain their metabolic functions even in extreme heat.

(B) In bacteria,the sex factor is known as the $F$-factor or $F$-plasmid (Fertility factor).
This plasmid contains the genes necessary for the formation of the sex pilus,which is required for the process of conjugation.
During conjugation,the $F$-plasmid is transferred from the donor cell $(F^+)$ to the recipient cell $(F^-)$,thereby converting the recipient into a donor cell.
Therefore,the correct option is $B$.

(A) The microorganisms that can survive and multiply at extremely high temperatures $(100-105^{\circ}C)$ are known as hyperthermophiles.
These organisms belong to the domain $Archaea$.
Specifically,certain species of archaebacteria,such as those found in deep-sea hydrothermal vents,are adapted to thrive in these extreme conditions due to the unique structure of their cell walls and membranes.
Therefore,the correct category is marine archaebacteria.

(B) Photolithotrophs are organisms that use light (photo) as their energy source and inorganic compounds (litho) as their electron donor (source of $H$ or electrons).
Therefore,they obtain energy from radiation and $H$ from inorganic compounds.

(A) Cyanobacteria are photosynthetic prokaryotes that perform oxygenic photosynthesis,meaning they release $O_2$ as a byproduct.
Many species of Cyanobacteria (e.g.,Nostoc,Anabaena) are capable of nitrogen fixation,a process catalyzed by the enzyme nitrogenase.
Since they perform oxygenic photosynthesis and possess the nitrogenase enzyme for nitrogen fixation,they are characterized as oxygenic with nitrogenase.

(D) Archaebacteria are considered the oldest living organisms because they possess unique cell wall structures (lacking peptidoglycan) that allow them to survive in extreme environmental conditions,such as high temperatures,high salinity,and acidic environments. They are believed to be the ancestors of modern bacteria and eukaryotes. Therefore,they are often referred to as the 'oldest living organisms'.

(A) Plasmids are small,circular,double-stranded $DNA$ molecules that are distinct from a cell's chromosomal $DNA$.
They are found in bacteria and some other microorganisms.
These are considered extra-chromosomal genetic elements because they exist and replicate independently of the main bacterial chromosome.
Plasmids often carry genes that provide advantages to the bacteria,such as antibiotic resistance.

(B) Organisms that derive energy from the oxidation of reduced inorganic substances (such as ammonia, nitrites, or sulfides) are known as $Chemosynthetic$ autotrophs. These organisms play a vital role in recycling nutrients like nitrogen, phosphorus, iron, and sulfur in the ecosystem. Unlike photosynthetic organisms, they do not require sunlight for energy production.

(C) Barophilic prokaryotes,also known as piezophiles,are organisms that thrive at high atmospheric pressures.
These organisms are typically found in deep-sea environments,such as deep-sea sediments or hydrothermal vents,where the pressure is significantly higher than at the surface.
They have evolved specialized cellular structures and metabolic pathways to function optimally under these extreme pressure conditions.
Therefore,the correct description is that they grow and multiply in deep sea sediments.

(C) Mycoplasma are organisms that completely lack a cell wall.
Because they lack a cell wall,they are naturally resistant to antibiotics like penicillin,which work by inhibiting cell wall synthesis.
Therefore,the statement that they are sensitive to penicillin is incorrect.
They are also known as $PPLO$ (Pleuropneumonia-like organisms),they exhibit pleomorphism (change shape),and many species are pathogenic in both plants and animals.

(A) Thermococcus,Methanococcus,and Methanobacterium belong to the domain $Archaea$.
These organisms are known as Archaebacteria.
$A$ key characteristic of many Archaebacteria,particularly those in the $Euryarchaeota$ phylum,is the presence of histone-like proteins that are homologous to the core histones found in Eukaryota.
These proteins help in the packaging of $DNA$ into nucleosome-like structures,which is a feature shared with eukaryotes,distinguishing them from typical eubacteria.

(A) Hyperthermophilic organisms that thrive in extremely acidic environments (acidophiles) are primarily found within the domains $Eubacteria$ and $Archaea$. Many members of the domain $Archaea$,specifically those in the group $Crenarchaeota$,are well-known for being both hyperthermophilic and acidophilic. Similarly,certain species of $Eubacteria$ have adapted to survive in such extreme conditions. Therefore,these organisms are classified into these two distinct domains.

(A) Methanogens are a group of archaebacteria that produce methane $(CH_4)$ as a metabolic byproduct in anoxic conditions.
These organisms are commonly found in the gut of several ruminant animals such as cows and buffaloes.
In the gut,they help in the breakdown of cellulose and are present in the excreta (dung) of these animals.
Therefore,they are found in abundance in cattle yards where cattle dung is present.

(C) The kingdom $Monera$ exhibits the most extensive nutritional diversity among all biological kingdoms.
Members of this kingdom can be autotrophic (photosynthetic or chemosynthetic) or heterotrophic (saprophytic,parasitic,or symbiotic).
This metabolic versatility allows them to survive in diverse and extreme environments,which is not observed to the same extent in other groups like $Plantae$ (mostly autotrophic) or $Animalia$ (mostly heterotrophic).

(D) The cell wall is a rigid layer present outside the plasma membrane in plants,fungi,and most bacteria.
$A$. $Penicillium$ is a fungus and possesses a chitinous cell wall.
$B$. $Agaricus$ is a fungus and possesses a chitinous cell wall.
$C$. $Volvox$ is a green alga and possesses a cellulosic cell wall.
$D$. $Mycoplasma$ is a genus of bacteria that lacks a cell wall entirely.
Therefore,$Mycoplasma$ is the correct organism where the cell wall is absent.

(D) Cyanobacteria are photosynthetic prokaryotes that contain chlorophyll $a$,similar to green plants. Due to their ability to perform oxygenic photosynthesis and their characteristic blue-green pigmentation,they are commonly referred to as blue-green algae.

(A) Archaebacteria are unique organisms that can survive in some of the most extreme environmental conditions on Earth.
These conditions include high salinity (halophiles),extreme temperatures (thermophiles),and highly acidic environments.
Deep-sea hydrothermal vents are characterized by extremely high temperatures and high pressure,which are conditions where only $Archaebacteria$ (specifically thermoacidophiles) can thrive.
Therefore,the correct option is $A$.

(D) In some prokaryotes like cyanobacteria,there are other membranous extensions into the cytoplasm called chromatophores which contain pigments.
These structures are responsible for photosynthesis in these organisms.
Heterocysts are specialized cells for nitrogen fixation,basal bodies are associated with flagella,and pneumatophores are respiratory roots in plants.

(A) Chromatophores are specialized membranous extensions into the cytoplasm in some prokaryotes,such as cyanobacteria. These structures contain pigments that are essential for the process of photosynthesis. Therefore,they are involved in photosynthesis.

(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 help in the breakdown of cellulose in the digestive tract of these animals.
They are responsible for the production of methane (biogas) from the dung of these animals.

(A) Mycoplasma are the smallest known living cells that can survive without oxygen. They completely lack a cell wall,which makes them naturally resistant to many antibiotics like penicillin that target cell wall synthesis. Many species of Mycoplasma are pathogenic to both plants and animals.

(C) Nitrogen fixation is the process of converting atmospheric nitrogen into ammonia,which is essential for plant growth.
$Nostoc$,$Azotobacter$,and $Anabaena$ are well-known nitrogen-fixing organisms.
$Nostoc$ and $Anabaena$ are cyanobacteria (blue-green algae) that possess specialized cells called heterocysts for nitrogen fixation.
$Azotobacter$ is a free-living soil bacterium that also fixes nitrogen.
$Spirogyra$ is a filamentous green alga that performs photosynthesis but lacks the ability to fix atmospheric nitrogen.
Therefore,the correct answer is $Spirogyra$.

(B) Blue-green algae,also known as $Cyanobacteria$,are photosynthetic prokaryotic organisms.
They lack a well-defined nucleus and membrane-bound organelles.
According to the $Whittaker$ classification system,they are placed under the Kingdom $Monera$,which consists of all prokaryotic organisms.
Therefore,they are classified as prokaryotes.

(B) $Eukaryote$ is an organism whose cells contain a nucleus and other membrane-bound organelles.
$Paramecium$ $caudatum$,$Euglena$ $viridis$,and $Amoeba$ $proteus$ are all unicellular eukaryotic protists.
$Escherichia$ $coli$ $(E. coli)$ is a bacterium.
Bacteria are $Prokaryotes$,which lack a defined nucleus and membrane-bound organelles.
Therefore,$Escherichia$ $coli$ is not a $Eukaryote$.

(D) The correct answer is $D$.
$A$: Cyanobacteria (blue-green algae) are photosynthetic prokaryotes that lack flagella throughout their life cycle. This statement is correct.
$B$: Mycoplasma are the smallest known living cells and they completely lack a cell wall,making them resistant to many antibiotics. This statement is correct.
$C$: The cell wall of bacteria is made up of peptidoglycan (murein). This statement is correct.
$D$: Pili and fimbriae are surface structures of bacteria. Pili are involved in conjugation (transfer of $DNA$),and fimbriae are involved in attachment to rocks or host tissues. Neither of these structures is involved in motility. Flagella are the primary structures responsible for bacterial motility. Therefore,this statement is incorrect.

(C) Transformation is a process of horizontal gene transfer in which a bacterium takes up naked $DNA$ fragments from its surrounding environment.
This process was first discovered by Frederick Griffith in $1928$ during his experiments with $Streptococcus$ $pneumoniae$.
The $DNA$ taken up by the competent bacterial cell is incorporated into its own genome,potentially altering its genetic characteristics.
Option $A$ refers to transduction,while option $B$ refers to conjugation.

(D) Spliceosomes are complex molecular machines primarily composed of small nuclear ribonucleoproteins $(snRNPs)$ and proteins. They are responsible for the splicing of pre-messenger $RNA$ $(pre-mRNA)$ to remove introns and join exons. This process is a characteristic feature of eukaryotic cells. Bacteria are prokaryotes,which lack a membrane-bound nucleus and complex internal organelles like spliceosomes. Therefore,spliceosomes are not found in bacteria.

(A) Oxygenic photosynthesis is a process in which water $(H_2O)$ is used as an electron donor,resulting in the release of oxygen $(O_2)$ as a byproduct.
Cyanobacteria,such as $Oscillatoria$,are the only prokaryotes that perform oxygenic photosynthesis,similar to green plants.
$Rhodospirillum$ (purple non-sulfur bacteria),$Chlorobium$ (green sulfur bacteria),and $Chromatium$ (purple sulfur bacteria) are examples of anoxygenic photosynthetic organisms that use substances like hydrogen sulfide $(H_2S)$ instead of water,and thus do not evolve oxygen.

(D) Heterotrophic bacteria are the most abundant bacteria in nature.
Many of these are important to human beings in making curd from milk (e.g.,$Lactobacillus$),production of antibiotics (e.g.,$Streptomyces$),fixing nitrogen in legume roots,etc.
They act as decomposers and play a vital role in nutrient cycling.

(C) The kingdom $Monera$ (which includes bacteria) exhibits the most extensive nutritional diversity among all biological groups.
Bacteria can be autotrophic (photoautotrophic or chemoautotrophic) or heterotrophic (saprophytic,parasitic,or symbiotic).
This metabolic versatility allows them to survive in diverse and extreme environments,unlike other kingdoms which have more restricted modes of nutrition.

(B) An organism that does not possess a true nucleus (nucleus with nuclear membrane) and double membrane-bounded organelles is called a prokaryote.
Kingdom Monera consists of prokaryotes,such as bacteria (e.g.,$Mycobacterium$) and cyanobacteria (e.g.,$Nostoc$ and $Oscillatoria$).
In contrast,$Saccharomyces$ (yeast) belongs to the Kingdom Fungi. It possesses a true nucleus and membrane-bound organelles,making it a eukaryote.