Monera (Prokaryotes) Questions in English

(D) The disease known as bovine pleuropneumonia was first recorded and studied by $Nocard$ and $Roux$ in $1898$. They were able to isolate the causative organism,which was later identified as a $Mycoplasma$ species. $Mycoplasma$ are unique bacteria that lack a cell wall,making them resistant to many common antibiotics.

(B) $Mycoplasma$ are the smallest known prokaryotic organisms that lack a cell wall.
Because they lack a rigid cell wall,they are not susceptible to osmotic lysis in the same way as bacteria with cell walls.
In the context of the phloem,which is a high-pressure environment,$Mycoplasma$ can survive because they are osmotically inactive or can adjust their internal osmotic pressure to match the environment,allowing them to exist without the need for a protective cell wall.

(C) $Mycoplasma$ are the smallest known living organisms that completely lack a cell wall.
Because they lack a rigid cell wall,they are unable to maintain their shape in hypotonic environments and are susceptible to osmotic lysis.
Therefore,they are considered osmotically fragile.

(B) Mycoplasma are the smallest known prokaryotic organisms that lack a cell wall.
Some species of Mycoplasma,such as Mycoplasma pneumoniae,are known to cause respiratory infections,but they can also lead to complications affecting the cardiovascular system,such as myocarditis or pericarditis.
Algae and Cyanobacteria are generally not known to cause cardiovascular diseases in humans.
Therefore,the correct option is $B$.

(C) $Mycoplasma$ species,such as $Mycoplasma$ $salivarium$,can infect the reproductive tract. They inhibit the supply of nutrients and blood to the developing embryo in pregnant women,which can lead to abortion.

(D) Mycoplasmas are the smallest known wall-less prokaryotes. They are known to cause various plant diseases.
$1$. Citrus greening is caused by Candidatus Liberibacter,but historically associated with mycoplasma-like organisms (MLOs).
$2$. Sandal spike disease is a classic example of a disease caused by phytoplasmas (a type of mycoplasma).
$3$. Grassy shoot of sugarcane is also caused by phytoplasmas.
Since these diseases are associated with mycoplasma or mycoplasma-like organisms,the correct answer is $D$.

(D) $Mycoplasma$ are organisms that completely lack a cell wall.
Since the Gram staining technique relies on the presence of a peptidoglycan cell wall to retain the crystal violet stain,$Mycoplasma$ cannot be classified as either Gram-positive or Gram-negative.
Therefore,they are considered to be Gram-indeterminate or simply lack the cell wall structure required for this classification.

(B) The organism $Mycoplasma \text{ } mycoides$ was first isolated by Noccard and Roux in $1898$ from cattle suffering from bovine pleuropneumonia.
Later, in $1929$, the name $Asterococcus \text{ } mycoides$ was proposed for this organism by Nowak.
Therefore, the correct option is $B$.

(D) Mycoplasma is a genus of bacteria that lack a cell wall around their cell membrane. Similarly,$L-$ form bacteria are strains of bacteria that have lost their cell walls due to mutation or environmental stress. Therefore,Mycoplasma is closely related to $L-$ form bacteria because both lack a cell wall.

(C) $Mycoplasma$ are the smallest known living organisms that lack a cell wall.
They exhibit diverse modes of nutrition.
Some species of $Mycoplasma$ are pathogenic and act as parasites in animals and plants,while others are saprophytic,living on dead and decaying organic matter.

(C) Mycoplasma are the smallest known living organisms that lack a cell wall. Like all other living cells,they contain both genetic materials,$DNA$ (deoxyribonucleic acid) as the primary genetic material and $RNA$ (ribonucleic acid) for protein synthesis. Therefore,the correct answer is that they contain both $RNA$ and $DNA$.

(B) The 'Witches' broom' disease in plants,including legumes,is characterized by an abnormal proliferation of shoots,resulting in a broom-like appearance.
This condition is primarily caused by $Mycoplasma$ (specifically $Phytoplasma$),which are wall-less prokaryotes that infect the phloem tissue of the host plant.
Therefore,the correct option is $B$.

(A) $Mycoplasma$ are the smallest known living organisms that can survive without oxygen. They are often considered intermediate between viruses and bacteria because they lack a cell wall (like viruses) but possess both $DNA$ and $RNA$ and can replicate independently (like bacteria).

(D) Prokaryotes are organisms that lack a membrane-bound nucleus and other membrane-bound organelles.
According to the $5$-kingdom classification,the kingdom $Monera$ consists of all prokaryotic organisms.
$Mycoplasma$ and blue-green algae (cyanobacteria) are both examples of prokaryotes.
$Ulothrix$ is a eukaryotic green alga,and $Fungi$ are eukaryotic organisms.
Therefore,the correct option is $D$.

(A) $Nostoc$ is a cyanobacterium. Cyanobacteria are Gram-negative bacteria that possess a complex cell envelope consisting of a three-layered structure: an outer membrane,a peptidoglycan layer,and an inner plasma membrane.
$Mycoplasma$ lacks a cell wall entirely.
$E. coli$ and $Rhodospirillum$ are bacteria,but the specific characteristic of a distinct three-layered cell envelope is a hallmark feature often associated with the cyanobacterial cell wall structure in the context of this question.

(B) $PPLO$ (Pleuro Pneumonia-Like Organisms),also known as $Mycoplasma$,are the smallest living cells known. They lack a cell wall and are pleomorphic. They reproduce primarily through the process of binary fission,which is a form of asexual reproduction where the cell divides into two identical daughter cells.

(A) Mycoplasmas lack a cell wall,which makes them highly flexible and allows them to change their shape easily.
Because of this,mycoplasmas are irregular and exhibit significant variability in their shape.
This characteristic is known as pleomorphism.

(B) $Mycoplasma$ are the smallest known living organisms that can survive without oxygen. They are unique because they lack a cell wall,which makes them naturally resistant to antibiotics like penicillin that target cell wall synthesis. They contain both $DNA$ and $RNA$ as genetic material and possess cytoplasm,distinguishing them from viruses,which lack cytoplasm and typically contain only one type of nucleic acid ($DNA$ or $RNA$).

(C) Mycoplasma are organisms that completely lack a cell wall.
They are the smallest living cells known and can survive without oxygen.
Due to the absence of a cell wall,they do not have a definite shape and are pleomorphic (can change their shape).
They are prokaryotic and lack a membrane-bound nucleus.

(B) $Mycoplasma$ are organisms that completely lack a cell wall.
$Penicillin$ is an antibiotic that functions by inhibiting the synthesis of peptidoglycan,which is a critical component of the bacterial cell wall.
Since $Mycoplasma$ do not possess a cell wall,$Penicillin$ has no target to act upon,making them naturally resistant or insensitive to this antibiotic.

(A) $Mycoplasma$ are the smallest living cells known and they can survive without oxygen.
They completely lack a cell wall,which is the rigid structure that provides a definite shape to most bacteria.
Because of the absence of a cell wall,$Mycoplasma$ are able to change their shape and size,a property known as pleomorphism.

(D) $Mycoplasma$ are the smallest living cells known and they completely lack a cell wall.
Because they lack a cell wall,they are pleomorphic and sensitive to antibiotics that target protein synthesis (like tetracycline),but they are resistant to penicillin which targets cell wall synthesis.
$Mycoplasma$ can survive and grow in cell-free culture media,meaning they are not obligate intracellular parasites.
Therefore,the statement that they are obligate intracellular parasites is incorrect.

(B) $Mycoplasma$ lacks a cell wall.
Therefore,the outermost limiting layer present in $Mycoplasma$ is the cell membrane.

(C) $PPLO$ stands for Pleuropneumonia-like organisms.
These are the smallest living cells known and belong to the genus $Mycoplasma$.
They lack a cell wall and can survive without oxygen.
Therefore, $PPLO$ are $Mycoplasma$-like organisms.

(C) An incipient nucleus (also known as a nucleoid) is a characteristic feature of prokaryotic cells,where the genetic material is not enclosed by a nuclear membrane.
$Myxophyceae$,commonly known as $Cyanobacteria$ or blue-green algae,belongs to the kingdom $Monera$.
Since $Myxophyceae$ are prokaryotes,they possess an incipient nucleus,whereas $Chlorophyceae$,$Rhodophyceae$,and $Phaeophyceae$ are eukaryotic algae.

(C) Heterocysts are specialized cells found in some filamentous cyanobacteria. Each heterocyst is connected to adjacent vegetative cells on two sides through prominent pores in the cell wall. These pores are often occupied by refractive cyanophycean granules known as polar nodules,which help in maintaining the specialized internal environment required for nitrogen fixation.

(C) $Nostoc$ is a genus of cyanobacteria that exists as colonies composed of filaments of moniliform cells. These colonies can be simple,consisting of a single layer or cluster of filaments,or compound,where multiple simple colonies are embedded within a common mucilaginous matrix. Therefore,$Nostoc$ can form both simple and compound colonies.

(C) The genus $Nostoc$ was named by the Swedish botanist $Vaucher$ in $1803$. The name is derived from a term used by the alchemist $Paracelsus$ to describe a gelatinous substance,but in the context of botanical nomenclature,$Vaucher$ is credited with the formal naming of the genus.

(C) $Nostoc$ species,such as $Nostoc$ $phycocearum$,are known to thrive in extreme cold environments like arctic and alpine meadows. Due to their ability to survive and grow in ice or freezing conditions,they are classified as cryophytic algae.

(A) In the cells of $Nostoc$ (a cyanobacterium), the protoplast is differentiated into two regions: the peripheral region and the central region.
The peripheral region contains pigments and is known as the $Chromoplasm$.
The central region is colourless and is known as the $Centroplasm$ or $Central body$.

(D) $Nostoc$ is a cyanobacterium, which is a type of prokaryotic organism.
$1$. Absence of a definite nucleus: Like all prokaryotes, $Nostoc$ lacks a membrane-bound nucleus and organized organelles.
$2$. Ability to fix nitrogen: Many prokaryotes, including various bacteria and cyanobacteria, possess the specialized machinery (nitrogenase enzyme) to fix atmospheric nitrogen.
$3$. Multiplication by fission: Binary fission is the primary mode of asexual reproduction in most prokaryotic organisms.
Since all these characteristics are typical of prokaryotic cells, the correct answer is $All \text{ the above}$.

(C) $Nostoc$ is a genus of cyanobacteria (prokaryotes).
Prokaryotic cells do not possess a well-defined nucleus or complex mitotic apparatus.
Therefore,they undergo simple cell division known as binary fission,which is a type of amitotic division.
Thus,the correct option is $C$.

(C) Blue-green algae (Cyanobacteria) are prokaryotic organisms.
They lack membrane-bound organelles,including cilia and flagella,which are responsible for motility in many other organisms.
However,some species of blue-green algae exhibit a slow,creeping movement known as gliding,which is often associated with the secretion of mucilage.
Therefore,the correct answer is $C$.

(D) Blue-green algae,also known as Cyanobacteria,are prokaryotic organisms.
$1$. They secrete a mucilaginous sheath composed primarily of pectin,which protects the colony.
$2$. They contain chlorophyll-$a$ and phycobiliproteins,specifically phycocyanin-$C$,which acts as a dominant accessory pigment giving them their characteristic blue-green color.
$3$. Being prokaryotes,they lack membrane-bound organelles,including plastids. Instead,their photosynthetic pigments are located in thylakoid membranes dispersed in the cytoplasm.
Therefore,all the listed features are characteristic of blue-green algae.

(C) $Nostoc$ is a genus of cyanobacteria (blue-green algae).
$1$. It lacks sex organs,as sexual reproduction is absent in cyanobacteria.
$2$. It also lacks motile cells (flagellated stages) in its life cycle.
Therefore,both sex organs and motile cells are absent in $Nostoc$.

(C) Blue-green algae,also known as $Cyanobacteria$,store their photosynthetic food reserves in the form of $Cyanophycean$ starch.
This starch is structurally very similar to $Glycogen$ and $Amylopectin$.
Therefore,the correct option is $C$.

(D) Cyanobacteria,being prokaryotic organisms,possess specialized structures for storage and metabolic functions.
$1$. Polyglucan granules (also known as cyanophycean starch) serve as storage bodies for carbohydrates.
$2$. Carboxysomes are proteinaceous microcompartments that contain the enzyme RuBisCO,essential for carbon fixation during photosynthesis.
$3$. Gas vacuoles are hollow,cylindrical structures that provide buoyancy,allowing the cyanobacteria to float at optimal depths for light absorption.
Since all these structures are characteristic of cyanobacteria,the correct answer is $D$.

(C) According to the research conducted by Bradley and Carr,nitrogen fixation in cyanobacteria (like Anabaena) occurs specifically within the specialized cells known as heterocysts. Heterocysts provide an anaerobic environment necessary for the activity of the enzyme nitrogenase,which is sensitive to oxygen.

(C) $Nostoc$ is a filamentous cyanobacterium. In its filaments,heterocysts are specialized cells responsible for nitrogen fixation. These heterocysts can be found at the terminal ends of the filament or interspersed between vegetative cells,which is known as an intercalary position. Therefore,heterocysts in $Nostoc$ can be both terminal and intercalary.

(C) Polyhedral bodies,also known as carboxysomes,are proteinaceous organelles found in many autotrophic bacteria,including cyanobacteria like $Nostoc$. These structures are involved in carbon fixation. Since $Nostoc$ is a type of cyanobacterium (a group of bacteria),it contains these polyhedral bodies.

(C) In $Nostoc$,the cells are arranged in a chain-like structure. When this filament of cells is present without its surrounding mucilaginous sheath,it is specifically referred to as a $Trichome$. Hyphae and Mycelium are terms associated with fungi,while a Colony refers to the entire aggregate of filaments.

(B) Sexual reproduction is a characteristic feature of Eukaryotic organisms.
$Nostoc$ is a Cyanobacterium (Prokaryote).
Prokaryotes do not undergo true sexual reproduction involving meiosis and gamete fusion.
$Ulothrix$ and $Volvox$ are green algae (Eukaryotes) that reproduce sexually.
$Aspergillus$ is a fungus (Eukaryote) that also exhibits sexual reproduction.

(C) Blue-green algae (Cyanobacteria) and bacteria both belong to the Kingdom $Monera$.
Members of the Kingdom $Monera$ are prokaryotic organisms.
Prokaryotes are characterized by the absence of a true,membrane-bound nucleus and membrane-bound organelles.
Therefore,the fundamental similarity between blue-green algae and bacteria is that both lack a true nucleus.

(D) Both cyanobacteria and bacteria belong to the kingdom $Monera$ and are classified as prokaryotes.
Prokaryotic cells are characterized by the absence of a membrane-bound nucleus and membrane-bound organelles like plastids or centrosomes.
However,both types of cells contain genetic material in the form of $DNA$,which is a fundamental requirement for all living organisms to store and transmit hereditary information.

(B) Cyanobacteria are photosynthetic prokaryotes that were historically classified as $Blue-green \text{ } algae$ due to their ability to perform oxygenic photosynthesis and their pigmentation. In the modern biological classification system, they are placed under the Kingdom $Monera$ as they are prokaryotic organisms.

(C) Cyanobacteria are photosynthetic prokaryotes that were historically classified as blue-green algae or Myxophyceae.
In modern biological classification,the term 'Cyanobacteria' is used to refer to these organisms,replacing the older,taxonomically incorrect term 'blue-green algae'.

(C) Blue-green algae,also known as cyanobacteria,are photosynthetic organisms that lack a membrane-bound nucleus and other membrane-bound organelles. Because of this cellular structure,they are classified as prokaryotes. They belong to the kingdom Monera in the five-kingdom classification system.

(B) Atmospheric nitrogen fixation is the process of converting atmospheric $N_2$ into ammonia $(NH_3)$,which can be utilized by plants.
$Anabaena$ is a genus of filamentous cyanobacteria that possesses specialized cells called heterocysts.
These heterocysts provide an anaerobic environment necessary for the enzyme nitrogenase to function,allowing the organism to fix atmospheric nitrogen.
$Funaria$ is a moss,$Chlamydomonas$ is a green alga,and $Fern$ gametophytes do not possess the capability to fix atmospheric nitrogen.

(D) Heterocysts are specialized,thick-walled cells found in some filamentous cyanobacteria like $Nostoc$.
$1$. They are typically found in an intercalary or terminal position.
$2$. They are the primary sites of nitrogen fixation because they provide an anaerobic environment for the enzyme nitrogenase.
$3$. They contain polar nodules,which are plug-like structures at the poles that regulate intercellular communication.
$4$. Heterocysts lack Photosystem $II$ $(PS-II)$,which is required for the photolysis of water and the evolution of oxygen. Since $CO_2$ fixation (Calvin cycle) requires $ATP$ and $NADPH$ (produced by light reactions),and the lack of $PS-II$ prevents the production of $NADPH$ via non-cyclic photophosphorylation,heterocysts are unable to perform $CO_2$ fixation.
Therefore,the statement that heterocysts have $CO_2$ fixation ability is incorrect.