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Give a brief account of viruses with respect to their structure and nature of genetic material. Also name four common viral diseases.
Viruses are nucleoproteins. The genetic material is protected within a protein coat, called capsid. The capsid consists of a number of subunits called capsomeres. The capsids are arranged in helical, polyhedral or geometric form. The genetic material, i.e., DNA or RNA may be single-stranded or doublRead more
Viruses are nucleoproteins. The genetic material is
See lessprotected within a protein coat, called capsid. The capsid
consists of a number of subunits called capsomeres. The
capsids are arranged in helical, polyhedral or geometric
form.
The genetic material, i.e., DNA or RNA may be
single-stranded or double-stranded.
The four common viral diseases are poliomyelitis,
rinderpest, dengue, potato mosaic.
Give a comparative account of the classes of kingdom-Fungi under the following
Classes of kingdom-Fungi are (i) Mode of nutrition Phycomycetes Saprotrophic and parasitic Ascomycetes Saprotrophic and parasitic Basidiomycetes Saprotrophic, parasitic and predaceous Deuteromycetes Parasitic and saprotrophic. (ii) Mode of reproduction Phycomycetes Asexual reproduction occurs by zooRead more
Classes of kingdom-Fungi are
See less(i) Mode of nutrition
Phycomycetes Saprotrophic and parasitic
Ascomycetes Saprotrophic and parasitic
Basidiomycetes Saprotrophic, parasitic and
predaceous
Deuteromycetes Parasitic and saprotrophic.
(ii) Mode of reproduction
Phycomycetes Asexual reproduction occurs by
zoospores (motile) or by aplanospores (non-motile).
Sexual reproduction is by gametangial fuston and
gametic fusion.
Ascomycetes Asexual reproduction is by conidia
and sexual reproduction is by gametangial contact,
spermatisation and somatogmny.
Basidiomycetes Asexual spores are generally not
found but vegetative reproduction by fragrnentation
is common. Sexual reproduction is by somatogamy.
Deuteromycetes Reproduce only by asexual spores
called conidia. Sexual reproduction is not reported.
Describe the cell structure of fungus in detail.
Fungus cells are eukaryotic. These cells contain all the eukaryotic organelles except plastids. Some of these organelles are nucleus, ribosomes, endoplasmic reticulum, mitochondria, Golgi bodies, etc. A fungal cell wall contains mostly chitin. Plasmalemma bears coiled membranous outgrowths called loRead more
Fungus cells are eukaryotic. These cells contain all the
See lesseukaryotic organelles except plastids. Some of these
organelles are nucleus, ribosomes, endoplasmic
reticulum, mitochondria, Golgi bodies, etc. A fungal
cell wall contains mostly chitin. Plasmalemma bears
coiled membranous outgrowths called lomasomes.
Nuclei are small and connected to endoplasmic
reticulum. Nuclear division involves formation of
internal spindle. Vacuoles are small. Near the hyphal
tips, the cytoplasm contains small vesicles called
chitosomes. Food reserve is in the form of glycogen
and oil.
Define the term mycorrhiza. How are these associations affect a plant? Explain with examples.
Mycorrhiza is a mutually beneficial or symbiotic association of fungi with roots of higher plants. Orchids grow as epiphyte on plants, have their roots associated with fungi right from the seedling stage. Many orchids cannot survive without mycorrhizae associations. Many forest trees such as pines aRead more
Mycorrhiza is a mutually beneficial or symbiotic
See lessassociation of fungi with roots of higher plants.
Orchids grow as epiphyte on plants, have their roots
associated with fungi right from the seedling stage.
Many orchids cannot survive without mycorrhizae
associations. Many forest trees such as pines appear
stunted if mycorrhizal associations are absent. In the
presence of these associations, these plants absorb 2d
times more nitrogen, potassium and phosphorus
compared to without them.
Justify that lichens are the pioneer organisms.
Lichens are the pioneer organisms in the new terrarns which colonise bare rocks. mountains and clitfs. corrode the rocks and accumulate a certain amount mmerals and organic matter, The plants like mossess and grasses appear later in succession. utilising the first formed by lichens, Lichens thus. caRead more
Lichens are the pioneer organisms in the new terrarns
See lesswhich colonise bare rocks. mountains and clitfs.
corrode the rocks and accumulate a certain amount
mmerals and organic matter, The plants like mossess and
grasses appear later in succession. utilising the first
formed by lichens, Lichens thus. can convert a barren
area Into one that can support vegetation.
There is a myth that immediately after heavy rains in forest, mushrooms appear in large number and make a very large ring or circle, which may be several metres in diameter. These are called 'fairy rings'. Can you explain the myth of fairy rings in biological terms?
The fairy rings form as the mycelium of the fungus spreads in the soil from a central pomt. It grows peripherally, so that the younger hyphae Will apvxar almost in a circle. The forest cover contains sufficient organic matter and favourable conditions that cause young fungal hyphae to form compact mRead more
The fairy rings form as the mycelium of the
See lessfungus spreads in the soil from a central pomt. It grows
peripherally, so that the younger hyphae Will apvxar
almost in a circle. The forest cover contains sufficient
organic matter and favourable conditions that cause
young fungal hyphae to form compact masses that grow
Into mushrooms. This is the reason, the mushrooms
appear growing in a circle or ring.
Why the members of class-Deuteromycetes are considered the fungi imperfecti?
Deuteromycetes is an artificial class of fungi which he been created to include all those fungi (fungi imperfect/ in which sexual stage is either absent or not knovr Their mycelium is usually septate. Coenocytic forms am not known. Clamp connections, typical Basidiomycetes are absent. It is believedRead more
Deuteromycetes is an artificial class of fungi which he
See lessbeen created to include all those fungi (fungi imperfect/
in which sexual stage is either absent or not knovr
Their mycelium is usually septate. Coenocytic forms am
not known. Clamp connections, typical
Basidiomycetes are absent. It is believed that
members of Deuteromycetes are actually Ascomycetes r
which sexual reproduction is either absent or yet to
discovered.
Explain the structure of bacteriophage with the help of well-labelled diagram.
A bacteriophage consists of two main parts i.e., head and tail. Head The head is in the form of bipyramidal hexagonal prism. It consists of proteinaceous membrane enclosing a core of viral DNA. The DNA is double-stranded. Tail It is cylindrical. It has four components are (i) a central core. (ii) aRead more
A bacteriophage consists of two main parts i.e., head and
See lesstail.
Head The head is in the form of bipyramidal hexagonal
prism. It consists of proteinaceous membrane enclosing a
core of viral DNA. The DNA is double-stranded.
Tail It is cylindrical. It has four components are
(i) a central core.
(ii) a protein sheath surrounding the core.
(iii) a sheath connected to head by a collar and at distal end
to a hexagonal basal plate.
(iv) pins at the corners of basal plate. Basal plate also bears
six long tail fibres which are the organs of attachment
to the bacterial surface.
List out some living features of viruses.
Viruses have the followmg features that make them similar to living things (i) They have DNA or RNA. (ii) Their nucleic acid can undergo mutation. (iii) They can reproduce only in living host cells. (iv) They infect different types of host cells. (v) The nucleic acids of viruses are identical In comRead more
Viruses have the followmg features that make them
See lesssimilar to living things
(i) They have DNA or RNA.
(ii) Their nucleic acid can undergo mutation.
(iii) They can reproduce only in living host cells.
(iv) They infect different types of host cells.
(v) The nucleic acids of viruses are identical In
composition to those of other organisms.
Explain the terms
(i) Basidiocarp It may be minute or very large structure which bears basidia, e.g., Bracket fungi, puffballs. (ii) Basidia These are special reproductive bodies Of Basidiomycetes where karyogamy, meiosis and basidiospore formation occurs. (iii) Basidiospores These are meiospores of Basidiomycetes. BRead more
(i) Basidiocarp It may be minute or very large structure
See lesswhich bears basidia, e.g., Bracket fungi, puffballs.
(ii) Basidia These are special reproductive bodies Of
Basidiomycetes where karyogamy, meiosis and
basidiospore formation occurs.
(iii) Basidiospores These are meiospores of
Basidiomycetes. Basidiospores are borne at the tips of
sterigmata or outgrowths of basidia.