Fungi (Multicellular decomposers) Questions in English

(A) The term 'fungus' was first used by the Swiss botanist Gaspard Bauhin $(1560-1624)$.
He is well-known for his work in plant taxonomy and for introducing the binomial nomenclature system before Linnaeus.

(C) The correct answer is $C$.
$H.A. \text{ De Bary}$ is known as the "Father of Modern Mycology" and "Father of Plant Pathology".
He was a $German$ botanist who made significant contributions to the study of fungi and plant diseases.

(D) Mycology is the branch of biology concerned with the systematic study of fungi,including their genetic and biochemical properties,their taxonomy,and their use to humans as a source for tinder,traditional medicine,food,and entheogens,as well as their dangers,such as toxicity or infection. The term is derived from the Greek words $mykes$ (mushroom) and $logos$ (study).

(A) The rainy season is the most favorable for the growth of fungi.
This is because fungi thrive in conditions where the temperature is moderate to warm and humidity is high.
During the rainy season,the moisture content in the air and on surfaces is at its maximum,which facilitates the rapid germination of fungal spores and the extensive growth of mycelium.

(C) The correct answer is $C$.
Fungi do not possess true tissues like plants.
However,they form a specialized structure known as $Plectenchyma$ (or $Pseudoparenchyma$).
This is an interwoven mass of fungal hyphae (mycelium) that,in cross-section,resembles the parenchyma tissue of higher plants.

(C) $Neurospora$ $crassa$ is widely used in genetic studies,particularly in the study of biochemical genetics and recombination. Due to its ease of cultivation,short life cycle,and the ability to analyze all products of a single meiosis,it is frequently referred to as the '$Drosophila$ of the plant kingdom' or a 'laboratory weed' in the field of genetics.

(A) Saprophytic nutrition is a mode of nutrition in which an organism obtains its nutrients from dead and decaying organic matter.
Fungi are heterotrophic organisms that secrete digestive enzymes onto their food source and absorb the broken-down nutrients,making them the primary saprophytes in nature.
Cyanobacteria are photosynthetic autotrophs.
Viruses are obligate intracellular parasites and do not exhibit saprophytic nutrition.
Therefore,the correct option is $A$.

(B) The correct answer is $B$.
$Deuteromycetes$ are commonly known as imperfect fungi because only the asexual or vegetative phases of these fungi are known.
When the sexual forms of these fungi were discovered,they were moved into classes they rightly belong to (i.e.,$Ascomycetes$ or $Basidiomycetes$).
They possess septate and branched mycelium.
Since sexual reproduction is either absent or not reported in this group,they are classified under $Deuteromycetes$.

(C) $Conidia$ are non-motile spores produced asexually and exogenously by constrictions at the tips of specialized hyphae known as $conidiophores$.

(B) In fungi,the vegetative body is known as the thallus.
If the entire thallus is converted into reproductive structures (sporangia or gametangia),the fungus is termed as $Holocarpic$.
In contrast,if only a part of the thallus is converted into reproductive structures while the rest remains vegetative,it is called $Eucarpic$.
Therefore,the correct answer is $Holocarpic$.

(A) All fungi are $Heterotrophs$.
Fungi lack $chlorophyll$,which means they cannot perform photosynthesis to produce their own food.
They obtain their nutrition by secreting digestive enzymes into their environment to break down complex organic matter and then absorbing the resulting nutrients.
This mode of nutrition is known as heterotrophic nutrition,and organisms that exhibit this are called $Heterotrophs$.

(A) Chlorophyll is a green pigment found in photosynthetic organisms that allows them to produce their own food.
$A$. Fungi are heterotrophic organisms that lack chlorophyll and obtain nutrients through absorption.
$B$. Algae are autotrophic organisms that contain chlorophyll and perform photosynthesis.
$C$. Bryophyta are non-vascular land plants that contain chlorophyll.
$D$. Pteridophyta are vascular plants that contain chlorophyll.
Therefore,fungi do not contain chlorophyll.

(D) $T.S. Sadasivan$ is a renowned Indian mycologist known for his work on the physiology of infection by $Fusarium$.
Other famous Indian mycologists include $K.C. Mehta$,$B.B. Mundkur$,and $C.V. Subramanian$.

(B) Anton De Bary is known as the father of modern mycology and plant pathology. He demonstrated that fungi are the causative agents of many plant diseases,such as late blight of potato and rust of wheat,thereby establishing their parasitic nature in plants. While Robert Koch is famous for his postulates regarding bacterial pathogens,Anton De Bary's work specifically pioneered the study of fungal parasitism in plants.

(D) The body of a fungus consists of long,slender,thread-like structures called $Hyphae$.
These $Hyphae$ form a network known as $Mycelium$.
$Conidia$ are asexual spores,$Mycorrhiza$ is a symbiotic association between fungi and plant roots,and $Sporangium$ is a structure in which spores are produced.

(B) The genus $Penicillium$ belongs to the class $Ascomycetes$.
$Ascomycetes$,commonly known as sac fungi,include organisms like $Penicillium$,$Aspergillus$,$Claviceps$,and $Neurospora$.
These fungi are characterized by the formation of spores called conidia,which are produced exogenously on special mycelial branches called conidiophores.

(A) Saprophytes are organisms that obtain their nutrients from dead and decaying organic matter.
$A$ Mushroom is a type of fungus belonging to the class Basidiomycetes,which grows on dead and decaying organic matter and acts as a saprophyte.
Therefore,the correct option is $A$.

(A) The cell wall of fungi is composed of a complex polysaccharide known as $Chitin$.
$Chitin$ is a polymer of $N$-acetylglucosamine units.
Unlike plants,which have cell walls made of $Cellulose$,fungi rely on $Chitin$ for structural support and protection.

(A) facultative saprophyte is primarily a parasite that has the ability to survive as a saprophyte when its host is unavailable or under specific environmental conditions.
In this context,the organism is essentially parasitic by nature but possesses the flexibility to obtain nutrients from dead organic matter (saprophytic nutrition) if necessary.

(B) . Late blight of potato is a seed-borne disease caused by the oomycete $Phytophthora infestans$.
This disease is characterized by the appearance of brownish to blackish necrotic (dead) areas on the tips and margins of the leaflets, which eventually leads to the blighting and death of the entire leaf.
As a result of the destruction of the foliage, the photosynthetic capacity of the plant is severely reduced, leading to poor tuber formation and significant crop loss.

(A) . $Claviceps$ $purpurea$ is a fungus that causes ergotism in rye ($Secale$ $cereale$) and other plants.
It also produces a hallucinogenic drug called $LSD$ (Lysergic acid diethylamide).

(C) All fungi are heterotrophs in their mode of nutrition.
Fungi that obtain their nutrients by absorbing dissolved organic material from dead and decaying organic matter are known as saprophytes.
Therefore,the correct option is $C$.

(B) Fungi are classified into three categories based on their modes of nutrition:
$(a)$ Saprophytic: Fungi that absorb soluble organic matter from dead substrates.
$(b)$ Parasitic: Fungi that live on living plants and animals.
$(c)$ Symbiotic: Fungi that live in association with other organisms,such as lichens (with algae) or mycorrhiza (with roots of higher plants).

(D) . The members of the division $Basidiomycota$ (class $Basidiomycetes$) are commonly called 'Club fungi' because their spore-producing structures,known as basidia,are club-shaped.

(C) Aflatoxins are toxic secondary metabolites produced by certain species of fungi,primarily $Aspergillus\, flavus$ and $Aspergillus\, parasiticus$. These toxins are known to contaminate various crops and can cause severe health issues in humans and animals.

(B) Wart disease of potato is a serious fungal disease caused by the chytrid fungus $Synchytrium$ $endobioticum$.
This pathogen infects the tubers of the potato plant,leading to the formation of warty,cauliflower-like outgrowths on the surface of the tubers.
It is a soil-borne disease and is considered a quarantine pest in many countries due to its ability to persist in the soil for many years.

(C) The correct answer is $C$.
In higher fungi (Basidiomycetes), the septum is characterized by a specialized, barrel-shaped structure known as a dolipore septum $(Latin \, dolium = \text{a large jar})$.
This structure features a complex pore that allows for the controlled movement of cytoplasm and organelles between adjacent hyphal cells.

(C) Fungi are eukaryotic,heterotrophic organisms that reproduce through the formation of spores. Unlike plants such as Pteridophytes,Gymnosperms,or Dicots,Fungi do not possess any vascular tissues (xylem and phloem) for the transport of water and nutrients. Therefore,they are the correct choice as they produce spores and lack vascular structures.

(B) The mycelium of $Aspergillus$ consists of branched,septate hyphae.
Each cell within these hyphae contains multiple nuclei,making them multinucleate (coenocytic condition within septate structures).

(D) $Agaricus \ campestris$ is a common field mushroom.
$Morchella \ esculenta$ is an edible fungus known as $gucchi$.
$Podaxon \ prodaxis$ is also an edible fungus.
Therefore,all the given options are correct.

(A) In gametangial copulation,two gametangia come into contact and fuse completely to form a zygote or zygospore.
This process is characteristic of members of the class $Zygomycetes$.
Examples include $Rhizopus$ and $Mucor$.

(A) In fungi,the fusion of two haploid cells immediately results in diploid cells $(2n)$ in most groups.
However,in members of $Ascomycetes$ and $Basidiomycetes$,an intervening dikaryotic stage ($n + n$,i.e.,two nuclei per cell) occurs.
This condition is called a dikaryon,and the phase is known as the dikaryophase.
Eventually,the nuclei fuse to form a diploid zygote,followed by meiosis to produce haploid spores.
Therefore,dikaryon formation is characteristic of $Ascomycetes$ and $Basidiomycetes$.

(B) $Plasmogamy$ is the first stage of sexual reproduction in fungi,in which the cytoplasm of two motile or non-motile gametes fuses with each other.
In this process,the nuclei of the sex cells come close to each other but do not fuse immediately.
Thus,the resulting cell contains two nuclei per cell,which is known as a $dikaryon$ or $binucleate$ stage.

(D) In certain fungi,such as those belonging to the classes $Ascomycetes$ and $Basidiomycetes$,a phase occurs where two genetically distinct haploid nuclei exist within the same cell.
This condition is known as the dikaryotic phase or dikaryon.
These two nuclei do not fuse immediately after plasmogamy (fusion of cytoplasm) but remain separate for a period before karyogamy (fusion of nuclei) occurs.
Therefore,a dikaryotic cell contains two dissimilar haploid nuclei.

(C) Many scientists (Sachs,$1874$; Bessey,$1950$) believe that fungi,particularly the class Phycomycetes,have evolved from siphonaceous green algae.
Both groups share common features such as the presence of coenocytic thalli,flagellated zoospores,cytoplasmic streaming,and similar modes of sexual reproduction.
Therefore,Phycomycetes are commonly referred to as algal fungi.

(C) $Neurospora$ is widely used in genetic research because it is easy to grow and has a short life cycle.
It was famously used by Beadle and Tatum to propose the $one \text{ gene} - \text{one enzyme}$ hypothesis.
Due to its extensive use in genetic studies, $Neurospora$ is often referred to as the $Drosophila$ of the plant kingdom.

(D) The perfect stage of a fungus refers to the sexual phase,which involves the formation of spores through meiosis (meiospores).
$Zygospores$,$Ascospores$,and $Basidiospores$ are examples of sexual spores (meiospores) produced during the perfect stage.
$Mitospores$ are produced during the asexual phase (imperfect stage) of the fungus,typically through mitosis,such as conidia or sporangiospores.
Therefore,$Mitospores$ are not related to the perfect stage.

(B) Coprophilous fungi are those fungi that grow on the dung of animals.
$Pilobolus$ is a well-known example of a coprophilous fungus,often referred to as the 'dung cannon' due to its unique spore dispersal mechanism.
Therefore,the correct option is $B$.

(C) Fungal hyphae penetrate the host tissue through a combination of two primary mechanisms:
$1$. Mechanical pressure: The hyphal tip exerts physical force against the host cell wall.
$2$. Enzymatic degradation: Fungi secrete various extracellular enzymes,such as cellulases,pectinases,and proteases,which soften and degrade the host cell wall components,facilitating entry.

(D) Fungi are heterotrophic organisms that lack chlorophyll,meaning they cannot perform photosynthesis. In contrast,algae are autotrophic and contain chlorophyll. Additionally,the cell walls of fungi are composed of chitin,whereas the cell walls of algae are primarily composed of cellulose. Therefore,the correct distinction is that fungi lack chlorophyll and possess chitinous cell walls.

(D) The correct statement is that in mushrooms,gills produce basidia.
$1$. Toadstools are generally considered poisonous,not edible.
$2$. Rust fungi (like $Puccinia$) are heteroecious,meaning they require two different hosts to complete their life cycle.
$3$. Parathecium is a part of the apothecium (a type of ascocarp),not the fruiting body itself.
$4$. In Basidiomycetes (mushrooms),the basidia are produced on the surface of the gills (lamellae) located under the pileus (cap).

(C) Mushroom belongs to the class $Basidiomycetes$ of the kingdom $Fungi$.
$Agaricus$ is a common genus of mushrooms,often referred to as the gill mushroom.
$Mucor$ is a mold,$Saccharomyces$ is yeast,and $Penicillium$ is a mold used for antibiotic production.
Therefore,the correct option is $C$.

(D) Fungi are heterotrophic organisms that do not perform photosynthesis.
They store their reserve food material in the form of glycogen and oil droplets.
Starch is the reserve food material in plants,whereas glycogen is the primary storage polysaccharide in fungi and animals.

(A) Parasexuality is a mechanism of genetic recombination in fungi that does not occur within the regular sexual cycle.
In this process,plasmogamy (fusion of cytoplasm),karyogamy (fusion of nuclei),and haploidization (reduction of chromosome number) occur,but they do not follow the regular sequence or occur at specific,predetermined stages of the life cycle as seen in typical sexual reproduction.
This allows for genetic variation without the requirement of a complete meiotic cycle.

(D) The correct answer is $D$.
In Ascomycetes,the diploid nucleus undergoes meiosis followed by mitosis to produce $8$ (sometimes $4$) haploid ascospores.
These sexually produced ascospores are contained within a sac-like structure known as an ascus.

(C) Parasexuality was first discovered by Pontecorvo and Roper $(1952)$ in a fungus, $Aspergillus$ $\text{nidulans}$.
Parasexuality helps in genetic recombination without the involvement of meiosis and fertilization.

(A) $Puccinia \ graminis \ tritici$ is the fungal pathogen responsible for causing black rust (also known as stem rust) in wheat.
This fungus belongs to the class $Basidiomycetes$ and is a well-known plant pathogen that significantly impacts wheat production globally.

(B) The causal organism of red rot in sugarcane is $Colletotrichum$ $falcatum$.
It is a fungal disease that affects the stem of the sugarcane plant,leading to the internal reddening of the tissues and a characteristic alcoholic smell due to fermentation.

(C) The fruiting bodies of certain fungi are used as nutritious and delicious food, e.g., $Agaricus \text{ } bisporus$ and $A. \text{ } campestris$ (mushrooms).