Viruses, Viroids, Prions and Lichens Questions in English

(D) The viral capsid is the protein shell of a virus,which encloses its genetic material.
This protein shell is composed of smaller structural subunits known as capsomeres.
Since capsomeres are proteins,they are composed of amino acids linked by peptide bonds,forming a polypeptide chain.
Therefore,the correct description is that capsomeres are polypeptide chains.

(C) Viruses are non-cellular organisms that are characterized by having an inert crystalline structure outside the living cell. They are obligate parasites,meaning they can only replicate and show signs of life when they infect a host cell. Once they enter a host cell,they take over the machinery of the host cell to replicate themselves,thereby becoming active.

(C) Viruses are considered a connecting link between living and non-living organisms because they exhibit characteristics of both.
$1$. Non-living characteristics: They can be crystallized,lack a cellular structure,and cannot replicate outside a host cell.
$2$. Living characteristics: They contain genetic material ($DNA$ or $RNA$),can mutate,and can replicate inside a living host cell.

(A) $capsid$ is the protein shell of a virus, which encloses its genetic material ($DNA$ or $RNA$).
$Viruses$ are non-cellular organisms characterized by having an inert crystalline structure outside the living cell.
$Fungi$ have cell walls made of $chitin$.
$Viroids$ are infectious agents that consist only of a short strand of circular $RNA$ without a protein coat.
$Bacteria$ have cell walls made of $peptidoglycan$.
Therefore, the correct answer is $A$ (Virus).

(C) The term 'virus' was given by Louis Pasteur. In Latin,'virus' means 'venom' or 'poisonous fluid'. Pasteur used this term to describe the infectious agents that cause diseases,as they were found to be smaller than bacteria and could pass through bacterial-proof filters.

(A) Bacteria-proof filters are designed to trap bacteria and larger microorganisms due to their relatively large size.
Viruses are significantly smaller than bacteria,typically ranging from $20 \ nm$ to $300 \ nm$ in size.
Because of their extremely small size,viruses can easily pass through the pores of a bacteria-proof filter.
Fungi,algae,and lichens are multicellular or large unicellular organisms that are much larger than bacteria and are easily trapped by such filters.

(C) .$J$. Ivanowsky $(1892)$ recognized certain microbes as causal organisms of the mosaic disease of tobacco. These were found to be smaller than bacteria because they passed through bacteria-proof filters. This discovery marked the first identification of viruses.

(B) The capsid is the protein shell of a virus. It is composed of several oligomeric structural subunits made of protein called capsomeres. Since these capsomeres are chains of amino acids,the capsid is essentially made of polypeptides.

(C) Louis Pasteur coined the term $Virus$ (meaning venom or poisonous fluid) to describe the causative agents of infectious diseases. He demonstrated that these agents were smaller than bacteria and could pass through bacterial filters.

(B) Viroids are infectious agents that consist only of a short strand of circular,single-stranded $RNA$ without a protein coat (capsid).
In contrast,viruses (whether animal,plant,or bacteriophages) possess a genetic material enclosed within a protein coat called a capsid.

(A) The potato spindle tuber disease is caused by $Viroids$.
$Viroids$ are infectious agents that consist only of a short strand of circular,single-stranded $RNA$ without a protein coat.
They were discovered by $T.O. Diener$ in $1971$.
Unlike viruses,they lack a $Capsid$ (protein coat),which makes them smaller and distinct from viruses.

(D) bacteriophage (or simply phage) is a type of virus that infects and replicates within bacteria. The term is derived from 'bacteria' and the Greek word 'phagein' meaning 'to eat'. They are obligate parasites that use the host bacterial machinery to reproduce.

(C) Viroids are infectious agents that are smaller than viruses. They were discovered by $T.O. Diener$ in $1971$. They consist of a short strand of circular single-stranded $RNA$ without a protein coat (capsid). Because they lack a protein coat,they are smaller than viruses.

(B) Viroids are infectious agents that consist only of a short strand of circular,single-stranded $RNA$ without a protein coat (capsid).
In contrast,viruses possess a genetic material ($DNA$ or $RNA$) enclosed within a protein coat called a capsid.
Therefore,viroids are the infectious agents that lack a capsid.

(C) capsid is the protein shell of a virus,which encloses its genetic material. It consists of several oligomeric structural subunits made of protein called capsomeres. Therefore,a capsid is essentially a protein structure.

(B) Viroids are infectious agents that are smaller than viruses. They consist solely of a short strand of circular,single-stranded $RNA$ without a protein coat (capsid). In contrast,viruses consist of genetic material ($DNA$ or $RNA$) enclosed within a protein coat. Therefore,viroids are considered the smallest known infectious agents.

(C) The protective protein coat of a virus is known as the $Capsid$.
It is composed of protein subunits called $Capsomeres$.
The $Capsid$ protects the genetic material ($DNA$ or $RNA$) of the virus from environmental damage.

(D) In $1971$,$T$.$O$. Diener discovered a new infectious agent that was smaller than viruses and caused potato spindle tuber disease. These agents were named $Viroids$. They consist of a low molecular weight $RNA$ and lack the protein coat that is found in viruses.

(B) Lichens are symbiotic associations,i.e.,mutually useful associations,between algae and fungi.
The algal component is known as phycobiont,which is autotrophic and prepares food.
The fungal component is known as mycobiont,which provides shelter and absorbs mineral nutrients and water for its partner.
Thus,the correct answer is $B$ (Lichen).

(A) In lichens,the fungal component (mycobiont) is responsible for sexual reproduction. The male reproductive structures are known as spermogonia (or pycnidia),which produce spermatia. The female reproductive structures are known as ascogonia (or carpogonia). These structures are typically produced within the fruiting bodies (ascocarps) of the fungal partner.

(A) The fruiting bodies of lichens,which are produced by the fungal partner (mycobiont),are known as ascocarps.
Among these,the cup-shaped or saucer-shaped fruiting body is specifically called an $Apothecium$.
$Perithecium$ is flask-shaped,while $Hypothecium$ refers to the layer of hyphae located just below the hymenium in an ascocarp.

(B) Lichens reproduce asexually primarily through vegetative propagation and specialized structures.
$(i)$ Pycniospores (also known as pycnoconidia) are small,asexual spores produced in structures called pycnidia.
$(iv)$ Soredia are small,powdery propagules consisting of a few algal cells wrapped in fungal hyphae,which are highly effective for vegetative dispersal.
Therefore,asexual reproduction in lichens occurs through $(i)$ Pycniospores and $(iv)$ Soredia.

(B) Lichens are symbiotic associations between algae and fungi.
In this association,the algal component is known as the $phycobiont$,and the fungal component is known as the $mycobiont$.
Both components live in a mutually beneficial relationship where the algae provide food through photosynthesis,and the fungi provide protection,anchorage,and absorption of minerals for the algae.
Therefore,the fungal component is called the $mycobiont$.

(A) Lichens represent a symbiotic association between algae and fungi.
$1$. The algal component is known as the $Phycobiont$,which is autotrophic because it contains chlorophyll and performs photosynthesis.
$2$. The fungal component is known as the $Mycobiont$,which is heterotrophic as it lacks chlorophyll and depends on the algae for food.
$3$. The $Mycobiont$ provides protection,anchorage,and absorption of minerals and water for the $Phycobiont$.
Therefore,the correct statement is that the $Phycobiont$ is autotrophic and the $Mycobiont$ is heterotrophic.

(B) The correct matches are as follows:
$1$. Ivanowsky: He was the first to discover $TMV$ (Tobacco Mosaic Virus) in $1892$ $(1-u)$.
$2$. Tulasne: He is known for his work in mycology,the study of fungi $(2-t)$.
$3$. Diener: He discovered viroids in $1971$ $(3-p)$.
$4$. Beijerinck: He demonstrated that the extract of infected tobacco plants could cause infection in healthy plants and coined the term 'Contagium vivum fluidum',which is associated with the naming/concept of viruses $(4-r)$.
Therefore,the correct sequence is $1-u, 2-t, 3-p, 4-r$.

(D) The correct answer is $D$.
$1$. The discovery of Viroids is attributed to $T.O. Diener$ $(1971)$.
$2$. The discovery of Viruses is attributed to $D.J. Ivanowsky$ $(1892)$.
$3$. The term 'Lichen' was first used by $Theophrastus$,but the systematic study is often associated with $Tulane$.
$4$. $Shiv Ram Kashyap$ is known as the 'Father of Indian Bryology',not the 'Father of Phycology'. The 'Father of Phycology' is $F.E. Fritsch$.

(A) In lichens,the fungal component (mycobiont) is responsible for sexual reproduction. The sexual reproductive structures,specifically the fruiting bodies that produce spores,are known as apothecia (singular: apothecium) or perithecia. Among the given options,the apothecium is the characteristic cup-shaped fruiting body found in many lichens where sexual spores are formed.

(C) Lichens represent a symbiotic association between an algal component (phycobiont) and a fungal component (mycobiont).
In this relationship,the algae provide food through photosynthesis,while the fungi provide protection,anchorage,and absorption of minerals and water for the algae.
Since both organisms benefit from this association,it is classified as a symbiotic mode of nutrition.

(B) Lichens are symbiotic associations between algae and fungi.
In this association,the algal component is known as the phycobiont,and the fungal component is known as the mycobiont.
The phycobiont is typically an alga (or cyanobacteria),which is capable of photosynthesis.
Since it performs photosynthesis,it is autotrophic and provides food for the fungus.
Therefore,the phycobiont is autotrophic.

(A) Lichens represent a symbiotic relationship between algae (phycobiont) and fungi (mycobiont).
In this association,the algal component provides food through photosynthesis,while the fungal component (mycobiont) provides protection,anchorage,and absorbs water and minerals.
Since fungi are heterotrophic organisms,they cannot synthesize their own food,which is why they rely on the algal partner.
Therefore,both Assertion $A$ and Reason $R$ are true,and $R$ correctly explains why this symbiotic relationship exists.

(C) Lichens are symbiotic associations between fungi and algae or cyanobacteria. $Strigula$,$Parmelia$,and $Usnea$ (commonly known as 'dagadphool') are well-known examples of lichens. $Anthoceros$ is a genus of hornworts,which belongs to the division Bryophyta,not the kingdom Fungi or the lichen group. Therefore,$Anthoceros$ is not a lichen.

(D) Lichens are classified into three main growth forms based on their morphology:
$1$. $Crustose$: These form a thin,crust-like layer closely attached to the substrate.
$2$. $Foliose$: These have leaf-like,flattened,lobed structures.
$3$. $Fruticose$: These are branched,shrub-like,or hanging structures.
$Filamentous$ is not a recognized morphological growth form category for lichens in standard biological classification.

(C) Lichens are symbiotic associations,i.e.,they are mutually useful associations,between algae and fungi.
The algal component is known as phycobiont (which is autotrophic and prepares food),and the fungal component is known as mycobiont (which provides shelter and absorbs mineral nutrients and water for its partner).
Therefore,the correct option is $C$.

(C) Lichenology is the branch of biology that deals with the scientific study of lichens. Lichens are composite organisms consisting of a symbiotic association of a fungus (mycobiont) and an alga or cyanobacterium (phycobiont). Therefore,the study of lichens is known as Lichenology.

(A) Lichens are symbiotic associations between algae and fungi.
In this association,the algal component is known as the phycobiont,while the fungal component is known as the mycobiont.
The phycobiont is autotrophic and prepares food for the lichen,whereas the mycobiont provides protection,anchorage,and absorbs water and minerals for the association.

(B) Lichens are symbiotic associations between algae and fungi.
$1$. The algal component is known as the $Phycobiont$,which is autotrophic and prepares food through photosynthesis.
$2$. The fungal component is known as the $Mycobiont$,which is heterotrophic and provides protection,anchorage,and absorption of minerals and water for the algae.
Therefore,the $Mycobiont$ is the heterotrophic component.

(A) Lichens represent a symbiotic association between algae $(phycobiont)$ and fungi $(mycobiont)$.
In this association,the algal component is responsible for photosynthesis,which produces food for both the alga and the fungus.
The fungal component provides protection,absorbs water,and provides mineral nutrients from the substrate for the alga.

(B) Lichens are symbiotic associations between fungi and algae. In lichens,the fungal component (mycobiont) is responsible for sexual reproduction. The sexual reproductive structures produced by the fungal partner are typically fruiting bodies known as $Apothecia$ (cup-shaped) or $Perithecia$ (flask-shaped). These structures contain asci,which produce ascospores. Among the given options,$Apothecia$ is the most commonly recognized structure for sexual reproduction in lichens.

(D) Lichens are classified based on their growth forms into three main types:
$1$. Crustose lichens: These form a thin,crust-like layer on the substrate.
$2$. Foliose lichens: These have a leaf-like,flattened body.
$3$. Fruticose lichens: These have a branched,shrub-like,or hanging body.
Therefore,all the given options are correct types of lichens.

(B) $soredium$ (plural: $soredia$) is a small,asexual reproductive unit found in lichens. It consists of a few algal cells (phycobiont) surrounded by fungal hyphae (mycobiont). These structures are dispersed by wind or water and can develop into a new lichen thallus under favorable conditions. Therefore,it is a common method of vegetative propagation in lichens.

(D) The symbiotic association between algae and fungi is known as $Lichen$.
In this association,the algal component is called $Phycobiont$ (which is autotrophic and prepares food),and the fungal component is called $Mycobiont$ (which provides protection,anchorage,and absorbs water and minerals for the algae).
$Mycorrhiza$ is a symbiotic association between fungi and the roots of higher plants.

(C) Lichens are symbiotic associations between algae and fungi.
In this association,the algal component is known as the $Phycobiont$ (or $Autotroph$),which prepares food through photosynthesis.
The fungal component is known as the $Mycobiont$ (or $Heterotroph$),which provides protection,anchorage,and absorbs water and minerals for the partner.

(C) Lichens reproduce asexually through various specialized structures.
Common methods include fragmentation,soredia,isidia,and the production of specific spores.
Oidia (also known as oidia-like spores) and pycniospores are recognized types of asexual spores produced by the fungal component (mycobiont) of the lichen.
Therefore,both $(A)$ and $(B)$ are considered methods of asexual reproduction in lichens.

(C) The fruiting bodies of lichens,which are primarily produced by the fungal partner (mycobiont),are generally referred to as ascocarps. Depending on their shape and structure,these are classified into two main types:
$1$. Apothecium: $A$ cup-shaped or disc-shaped fruiting body.
$2$. Perithecium: $A$ flask-shaped fruiting body with a small pore (ostiole) at the top.
Since both terms represent types of lichen fruiting bodies,the correct answer is that they can be either $(A)$ or $(B)$.

(D) Lichens are classified based on their growth forms into three main types: $1$. Crustose (Crust-like),$2$. Foliose (Leaf-like),and $3$. Fruticose (Shrub-like). 'Crystalline lichen' is not a recognized morphological classification of lichens. Therefore,option $D$ is the incorrect type.

(A) Viruses are considered a bridge or link between living and non-living organisms because they lack independent metabolic machinery.
In a free state (outside a host),viruses are inert and act like non-living chemical particles (crystallizable).
However,once they enter a host cell,they hijack the host's cellular machinery to replicate,thus exhibiting characteristics of living organisms.
Therefore,both the assertion and the reason are correct,and the reason provides the correct explanation for why viruses are considered a link between living and non-living entities.

(C) Assertion $(A)$ is true: The protein coat of a virus,known as the capsid,is composed of small subunits called capsomeres,which protect the nucleic acid.
Reason $(R)$ is false: Viruses are inert outside their specific host cells. They do not exhibit any metabolic activity or 'living' behavior in a virus-free state; they only replicate when they infect a living host cell.

(C) Viroids are infectious agents discovered by $T.O. Diener$ in $1971$.
They consist of a low molecular weight $RNA$ and lack the protein coat that is found in viruses.
Therefore,Assertion $(A)$ is true.
Viroids contain a short strand of $RNA$,not $DNA$.
Therefore,Reason $(R)$ is false.

(D) Assertion $(A)$ is false because Parkinson's disease is a neurodegenerative disorder,not an infectious disease caused by viroids. Viroids are infectious $RNA$ particles that primarily cause diseases in plants (e.g.,Potato Spindle Tuber disease).
Reason $(R)$ is true because viroids consist only of a short strand of circular single-stranded $RNA$ without a protein coat,making them significantly smaller than viruses.

(A) Viroids are infectious agents that are smaller than viruses.
They consist solely of a short strand of low molecular weight $RNA$.
Crucially,they lack the protein coat (capsid) that is found in viruses.
Therefore,they are defined as free $RNA$ molecules without a protein coat.