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PlantKingdom
Introduction
Eichler classified PlantKingdom into 2 sub-kingdoms and 4 divisions.
Sub-kingdom Cryptogams are seedless, non-flowering plants and has divisions Thallophyta,
Bryophytaand Pteridophyta.
Thallophytes are embryolessatracheophytes with non-jacketed sex organs. It has the subdivisions Algae
and Fungi.
Algae are autotrophicthallophytes which show progressive development of sexual reproduction.
Fungi are heterotrophicthallophytes which show progressive degeneration of sexual reproduction.
Bryophytes are atracheateembryophytes with stalked jacketed sex organs, sporophyte as parasite on
gametophyte and has Haplontic life cycle.
Pteridophytes are tracheate cryptogams with sessile jacketed sex organs, independent gametophyte and
sporophyte and has diplohaplontic life cycle.
Sub-kingdom Phanerogams has seeded plants with Siphonogamousoogamy. It has division
Spermatophyta with subdivisions as Gymnosperms and Angiosperms.
Gymnosperms are archegoniates with naked seeded plants showing only single fertilization.
Angiosperms are non-archegoniate spermatophytes consisting of Dicots and Monocots.
Spirogyra:
It is commonly called as Pond Scum (Free floating species), Pond silk and Water silk.
Thallus is unbranched filamentous, multicellular, uniseriate with polarity in free floating species and
with polarity in attached species (S. jogensis, S. adnata).
It has cylindrical cells with pectocellulosic wall, haploid nucleus suspended in the central large vacuole
and parietal 1-16 ribbon shaped chloroplasts having starch storing pyrenoids.
It vegetatively reproduces by Fragmentation and asexually by Akinete formation in S. farlowii and
Aplanospore formation in S. aplanosporum.
It sexually reproduces by Conjugation. It may be Scalariform conjugation (Physiological anisogamous
or Isogamous), Indirect lateral conjugation (Physiological anisogamous as in S.affinis) or Direct lateral
conjugation (Anisogamous as in S.jogensis, S. mirabilis).
Zygospore has triple layered wall, diploid nucleus, proplastids and oil droplets. During its germination it
shows meiosis and forms germ tube which later develops into filament.
Its life cycle is haplontic and diploid stage is limited to only Zygospore.
Questions from previous exams:
1.
[A]: In Spirogyra some cells in one of the two filaments become empty after conjugation. EAMCET-2006
[R]: The aplanogametes from the cells of one filament pass through the conjugation tubes into the cells of the other filament.
*1) Both A and R are true and R is the correct explanation of A
2) Both A and R are true but R is not the correct explanation of A
3) A is true but R is false
4) A is false but R is true
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2.
How many zygospores are formed in a 100 celled filament of Spirogyra affinis if all cells are involved in
conjugation?
1) 99
EAMCET - 2010
*2) 50
3) 49
4) 1
Some important Questions
1.
Arrange the following structures of Spirogyra cell in centripetal sequence
I. Tonoplast
II. Nucleolus
III.Cell membrane
IV. Thylakoids
1) III, I, IV, II
*2) III, IV, I, II
3) III, IV, II, I
4) IV, III, I, II
Rhizopus
It is saprophytic and commonly called as Bread mould, Black mould, Pinmouldand Weed of the
laboratory.
Mycelium is branched filamentous, aseptate, coenocytic and has Rhizoids, Stolons in vegetative stage.
Sporangiophores are formed during asexual reproduction.
Cell wall is chitinous, reserve food materials are glycogen, oil and has several vacuoles.
It reproduces vegetatively by fragmentation.
Asexual reproduction takes place by Sporangiospore formation and Chlamydospore formation.
Sporangiophores are formed opposite to rhizoids on the upper surface of stolons. It has terminal
sporangium.
Sporangium has peripheral nucleated (Sporoplasm) and central vacuolated region (Columelloplasm).
These are separated by a layer of dome shaped vacuoles which eventually fuse, form cleft into which a
wall is secreted.
Sporiferous zone is cleaved into small 2-10 or uninucleated bits which eventually secrete a thin wall to
transform into Sporangiospores. Columella enlarges and helps in the dehiscence of sporangial wall. The
spores are dispersed and later germinate to form Rhizopus mycelium.
Chlamydospores are thick walled spores formed singly in older hyphae during unfavourable conditions.
It sexually reproduces by Gametangialcoupulation. Heterothallic species (R. stolonifer) are more
common than Homothallic species (R.sexualis).
Trisporic acids regulate it in heterothallic species.
Zygophores of opposite strains give out copulating branches (Progametangia) at the point of contact
which become two celled (Suspensor and Gametangium), upon septum formation.
Gametangia fuse, Nuclei of opposite strains pair, fuse and form diploid nuclei and the structure is called
as Zygospore. Unpaired nuclei gradually degenerate.
Diploid nuclei of zygospore undergo meiosis to form haploid nuclei, exine is ruptured and
Promyceliumis fomed.
Tip of promycelium forms germ sporangium in which germspores are formed and eventully dispersed.
Life cycle is haplontic. Heterothallism was first discovered by Blackslee in R.stolonifer.
Questions from previous exams:
1.
Arrange the following in correct sequence with reference to sexual reproduction in Rhizopus. EAMCET - 09
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2.
I. Formation of Germ tube
II. Formation of Zygophores
III. Formation of Warty wall layer of Zygospore
IV. Secretion of Trisporic acid
1) IV, III, II, I
3) II, I, IV, III
*2) IV, II, III, I
4) I, III, II, IV
Identify the correct sequence of the stages in the life cycle of Rhizopus after the reduction division of Zygospores
EAMCET - 2010
*1) Promycelium – Germ sporangium – Germ spores - Mycelium
2) Promycelium – Germ spores – Germ sporangium - Mycelium
3) Mycelium – Promycelium – Germ spores – Germ sporangium
4) Promycelium – Mycelium – Germ sporangium - Zygospores
Important Questions
1.
A + strain progametangium of Rhizopusstolonifer has 108 nuclei and –strain progametangium 124 nuclei. Upon successful
completion of sexual reproduction, there is formation of 224 daughter mycelia. What must be the minimum number of nuclei
that each gemetangium is expected to contain.
1) 112
2.
2) 108
*3) 56
4) 224
Choose the incorrect set
*1) Promycelium – Diploid – Germ sporangium
2) Zygospore – Diploid – Double layered wall
3) Germ sporangium – Meiospores – No columella
4) Rhizopusstolonifer – Heterothallic – Physiological anisogamy
Funaria
Itis known as Cord moss, Fire moss and Mixohydric moss
The dominant stage in the life cycle Gametophyte has alga like Protonemalstage and adult
Gametophore with multicellular rhizoids having oblique cross walls, cauloid and phylloids.
Stem has dead hydroids that conduct mineral water.
It vegetatively reproduces by Secondary protonema, Gemmae and Tubers.
Gametophore is monoecious, autoicous, protandrous and sexually reproduces by
zooidogamousoogamy.
Male branch has multicellular stalked antheridia that producesbiflagellated chemotactic sickle
shaped male gametes, capitateparaphyses and perichaetial leaves.
Female branch has stalked archegonia with twisted neck, 6 tomany NCC, VCC that form sugary
mucilage, an egg cell and one (Neck) and Two layered (Venter) jacket, paraphyses and perichaetial leaves.
Sporophyte is semi-parasite on the female branch of gametophore, has Foot, Seta and spore
producing Capsule with photosynthetic Apophysis, fertile Theca and cap like Operculum with
Peristome (16 hygroscopic exostomal teeth, 16 endostomal teeth), Annulus and Rim.
Spore sac of theca produces haploidmeiospores due to meiotic divisions in spore mother cells that
have chloroplasts and oil droplets.
Peristome and Seta aid in spore dispersal.
Spores germinate and form protonema and buds of protonema form gametophores.
Life cycle is haplodiplontic and shows heteromorphic alternation of generations.
Questions from previous exams
1. Assertion(A): Life cycle in Funaria is diplohaplontic
Reason
(R): In Funaria, there is alternation of haploid gametophyte and diploid sporophytic phases, one
becoming parent to the other. EAMCET 2008
1) A and R are correct, R explains A
2) A and R are correct, R does not explain A
3) A is correct, R is wrong
*4) A is wrong, R is correct
Important questions
1.
[A]: Funaria is commonly called as Myxohydric moss
[R]: Conduction in Funaria takes place within stem as well as in between the adjacent gametophores
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*1) Both A and R are true and R is the correct explanation of A
2) Both A and R are true but R is not the correct explanation of A
3) A is true but R is false
4) A is false but R is true
2.
Arrange the following with gradual increase in the number of series of cells that they have
i) Archegonial neck
ii) Antheridial stalk
iii) Paraphyses
iv) Archegonial venter
*1) iii, ii, i, iv
2) iii, ii, iv, i
3) iii, i, ii, iv
4) ii, iii, i, iv
Pteris
Dominant stage is sporophyte which has perennial Rhizome,Imparipinnate leaves with open
dichotomous venation in leaflets which show circinate vernation and brown hair ramenta and adventitious
roots.
Rhizome has epidermis with thick cuticle, sclerenchymatous hypodermis, dictyosetele with
mesarch xylem.
Sporophyll has 2 sori per leaflet and sorus is mixed, linear and coenosorus type with false
indusium, placenta, paraphyses and leptosporangia.
Sporangium has pedicel, capsule with 1-layered jacket having hygroscopic annulus and stomium
with lip cells, 1-2 layered tapetum and 48 spores formed from 12 spore mother cells due to meiosis. Spores
have trilete.
Spores are dispersed by Sting/Catapult movement of Annulus.
Gametophyte is monoecious, protandrous, dorsiventral, anterior-posterior, cordate, parenchymatous
with discoid chloroplasts, has unicellular rhizoids, antheridia at the posterior and archegonia nearer to the
notch.
Antheridium is globose, has 3-celled jacket and 32multiciliated, highly coiled male gametes.
Archegonium has 16 jacket cells in 4 rows, a binucleate NCC, a VCC and egg. Its mucilage rich in
Malic acid attracts the male gametes (Chemotaxy).
Fertilization is zooidogamousoogamy. Embryo forms adult sporophyte that respectively forms
primary root, leaf, Rhizome and adventitious roots.
Life cycle is Diplohaplontic and Alternation of generations is heteromorphic.
Questions from previous exams
1.
Which of the following taxa shows zooidogamousoogamy ? EAMCET – 2009
I. Spirogyra
1) III, IV
II. Funaria
*2) II and III
III. Pteris
3) I and II
IV. Rhizopus
4) III and I
Important questions
1.
2.
Choose the incorrect statement
1) All leaflets of Pteris are similar in shape
*2) All leaflets of Pteris leaf are arranged in pairs
3) Leaflets of Pteris are dissimilar in size
4) Basal most leaflets of Pteris leaf are the smallest
Match the following with respect to Pteris
List – I
List – II
A) Cap cell
I) Dikaryotic cell
B) Neck canal cell
C) U shaped notch
D) Trilete
II)
III)
IV)
V)
Antheridium
Spore
Prothallus
Sporophyll
*1)
A
II
B
I
C
IV
D
III
2)
3)
4)
II
II
III
I
III
I
IV
IV
IV
V
I
II
Cycas
Genus Cycas is tropical or sub-tropical with 20 species .
Indian wild species of Cycas are C. circinalis (CrozierCycas occurs in deciduous forestes of South
India), C. beddomei (MadrasCycas – occurs on Tirumal Hills of A.P.), C. pectinata (NepalCycas –
Eastern India) and C. rumphii (RumphiousCycas – Andaman and Nicobar islands). C.revoluta (Sago
Cycas) is ornamental species.
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Its plant has caudex stem with persistent leaf bases, paripinnate foliage leaves with
circinatevernation, ramenta and some spinous leaflets, scale leaves and normal and coralloid (with BGA
Nostoc or Anabaena) adventitious roots.
Coralloid roots have periderm with lenticels (for gaseous exchange), cortex with drusses and BGA,
2-3 layered pericycle and Triarch xylem.
Pinnule is hypostomatous with sclerenchymatous hypodermis, differentiated mesophyll, Primary
and secondary transfusiontissue for lateral conduction and diploxylicpseudomesarchopen vascular
bundle. Cuticle is thick
It vegetatively reproduces by bulbils or adventitious buds formed at the basal region of stem
It is dioecious. Male cone has few sterile and many fertile Triangular, spirally arranged
microsporophylls with apical sterile apophysis and many microsori (2-6 sporangia) surrounded by
indusial 1 or 2 celled hairs on abaxial side.
Microsporangium has 5-6 layered wall with exothecium having thickened radial and tangential walls
and haploid pollen grains released at 3-celled stage.
Pollination is direct and anemophilous. Adult male gametophyte has prothaliial, vegetative, stalk
cells and 2 multiciliated top shaped largest male gametes. Pollen tube is haustorial in nature.
Megasporophyll has 2-12 largest ovules in two rows in the notches of margins of the middle region.
Ovules are vascularised, orthotropous, unitegmic (Tripartite), crassinucellate, with archegonial
chamber and pollen chamber formed by the degeneration of nucellus and forms multicellular female
gametophyte (Endosperm) with 2-8 archegonia after megasporogenesis.
Archegonia have 2 neck cells, VC nucleus and egg but lack NCC and venter. Fertilization is
siphonogamous and zooidogamous
Embryo respectively has haustorium, coiled suspensor, coleorhiza, radicle, hypocotyle, 2
cotyledons and plumule.
Seeds are haploid endospermic, perispermic, polyembryonic and ornithochorous and show
hypogeal germination.
Life cycle is diplohaplontic with heteromorphic alternation of generations.
Questions from previous exams
1. These characters are seen in Cycas.
EAMCET 2007
I. Motile male gametes
II. Haploid endosperm
III. Formation of sporophyte directly from gametophyte by apogamy
IV. Female gametophyte with archegonia
*1) I, II, IV
2) I, III
3) II and III
4) I, II, III
Important Questions
1.
False statement related to Cycas is
EAMCET - 2010
1) Motile male gametes and pollen tube are involved in fertilisation
2) Endosperm formation occurs before fertilisation
3) Ovule contains pollen chamber
*4) Gametophytic tissue is not found in seeds.
Microbiology
Bacteria
Roger Stanier opined for considering culture methods along with size of the organisms for defining
bacteria.
Microbes are omnipresent and play a role in recycling of elements; causing diseases, yielding antibiotics,
commercial production of enzymes, vitamins, alcohols etc.; dairy industry; sewage disposal; mining;
genetic engineering; biological control; exploration of life in outer space and biogas production.
Bacteria were discovered by Leeuwenhoek, named by Ehrenberg and extensively studied by Louis
Pasteur and Robert Koch.
They live freely or as saprophytes, parasites and symbionts (Rhizobium).
Epulopisciumfishelsoni and Thiomargaritanamibiensis are of monstrous size.
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On the basis of shape they are identified as Cocci, Bacilli, Spirillae, Vibrios and Pleomorphs
(Acetobacter).
Based on staining ability, they are classified as Gram -ve and Gram +ve bacteria.
Structurally they have peptidoglycan cell wall, Glycocalyx with polysaccharides, variously distributed
flagella made of flagellin, adhering appendages pili made of pilin, cell membrane with respiratory
functions, chlorosomes vesicles or photosynthetic cell membrane invaginations, some with gas vacuoles
(Halobacterium), nucleoid having only one circular chromosome made of DNA, some with
extrachromosomal DNA rings (plasmids) and reserve foods in the form of Glycogen or PBH.
Nutritionally bacteria are recognized as Photoautotrophs (Chlorobium, Chromatium), Photoheterotrophs
(Rhodo bacteria), Chemoautotrophs (Hydrogen, Nitrifying, Sulphur and Iron bacteria) and
Chemoheterotrophs (Saprophytes, Parasites and Symbionts).
They asexually reproduce by Binary Fission in favourable conditions and by Endospore formation
(Bacillus, Clostridium) in unfavourable conditions.
Though true sexual reproduction is absent they show genetic recombination by ways of Transformation
(Griffith in Streptococcus pneumoniae), Conjugation (Lederberg and Tatum in E.coli) and Transduction
(Zinder and Lederberg in Salmonella typhimurium).
They behave as friends to man because they are useful in Agriculture (Ammonifying, Nitrifying,
Diazotrophic and Bio-pesticidal bacteria); In Industries for the production of Acetone, Butonol
(Clostridium acetobutylicum), Vinegar (Acetobactersps.), Lactic acid (Lactobacillus), Propionic acid
(Propionibacterium), Ethanol (Zymomonasmobilis, Thermoanaerobacter), Fiber retting
(Clostridiumsps.), Curing of Tobacco (Bacillus sp.) and Tea (Micrococcus sp.) and Gobar gas
(Methanogenic bacteria) production.
They are used in the production of medicinal importance substances like Lysine (Corynebacterium) and
Antibiotics like Streptomycin, Chloremphenicol, Cycloheximide, Neomycin, Amphoterican,
Oxytetracyclin (Streptomycessps.), Bacitracin and Polymyxin B (Bacillussps.).
In the area of Biotechnology, E. coli,Agrobacterium and Brevibacterium are extensively used.
They behave as foes to man by spoiling the food stuffs and causing diseases in Plants (Xanthomonas,
Pseudomonas, Erwinia, Agrobacterium), Animals (Bacillus anthracis, Mycobacteriumsps., and Vibrio
tetus) and Man (Pasteurella, Neisseria, Treponema, Corynebacterium etc.).
Viruses
Viruses are infectious, ultramicroscopic, acellular, nucleoprotein particles
History : Edward Jenner (Vaccination), Louis Pasteur (term Virus and Rabies vaccine), Iwanowsky
(Virus TMV discovery), Beijerinck (ContagiumVivumFluidum), Stanley (TMV crystallization), Pierie
and Bawden (Virus as nucleoprotein), Gierer and Schramm (genetic and infectious nature of RNA),
FraenkelConrat (confirmed RNA as genetic material) and Andrew Lwoff ( a virus is a virus).
The techniques Ultracentrifugation, X-ray crystallography and Electron microscopy are used in
Virology.
Phytophages, Zoophages, Bacteriophages, Mycophages, Zymophages, Cyanophages are some of the
types of viruses based on host range.
Vaccinia virus is the largest (actually Mimivirus parasitic on amoeba) and smallest is f2 bacteriophage.
Viruses may be rod like (TMV), rectangular (Vaccinia virus), Polyhedral (Adenovirus), Spheroidal
(Polio virus), Tadpole shaped (Bacteriophage) and Bullet shaped (Rhabdo virus).
Chemically all viruses have protein coat Capsid made of capsomers and one of the nucleic acids which
may be ssRNA (TMV, Polio virus, Influenza virus), dsRNA (Reo virus, Wound Tumour virus, Rice
dwarf virus, Maize rough dwarf virus, Blue tongue virus, Bacteriophage φ6), ssDNA (Bacteriophages
M13 and φX174) and dsDNA (Most animal viruses, Bacteriophages, Cyanophages, CMV, DMV).
Most of the animal viruses have an additional carbohydro-lipoproteinaceous covering Peplos or
Envelope made of units Peplomers (HIV, Influenza virus).
Viral symmetry is based on arrangement of capsomers and can be Helical (TMV), Cubical (Adeno
virus) and Binal (Bacteriophage).
Infectious nucleic acid particles are called as Viroids (Potato spindle tuber virus, Citrus exocortosis
virus).
Infectious protein particles are called as Prions. They cause diseases such as Scrapie in Sheep and Mad
cow disease.
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TMV is 300 X 18-19 nm, its central hole is 4nm, 39 X 106daltonsmol.wt., capsid with helically arranged
capsomers, each capsomer with 158 amino acids and ssRNA having 6500 nucleotides.
Bacteriophage was discovered by Twort and named by Herelle. T4 Phage has a head with dsDNA (1000
times longer than Phage) and semipermeable capsid, a tail with core surrounded by sheath having 144
helically arranged capsomers and sealed by hexagonal end plate with 6 spikes and 6 jointed tail fibres, a
collar between Head and Tail.
Bacteriophages replicate by Lytic and Lysogenic cycle. Lytic cycle is shown by T even phages and has
1. Adsorption stage (Virus attaches to bacterium with tail fibres), 2. Penetration stage (Viral DNA is sent
into the bacterium after the action of lysozyme and contraction of tail sheath), 3.Latent stage (Viral DNA
takes over the functions of bacterium and destroys the bacterial DNA {Eclipse} and forms viral particles
by synthesizing capsid proteins and viral DNA {Maturation stage} and 4.Lytic stage in which the
bacterial cell wall is broken and viruses are released.
Lysogenic cycle is shown by λ bacteriophages in which the viral DNA is integrated into bacterial DNA
and carried to successive generations of bacteria.
Viral plant diseases are Chlorosis (Peach yellows), Mosaic (Tobacco mosaic), Vein clearing (Bhendi
vein clearing), Vein banding (Citrus vein banding), Ring spots (Tomato spotted wilt), Dwarfing (Rice
stunting), Malformation (Swollen shoot of Cocoa) and Floral break (Tulip mosaic break).
Viral diseases are transmitted through vegetative parts (In crops like Potato, Banana, Sugar cane),
Mechanical methods (Potato virus), Seeds (Bean, Lettuce mosaic), Pollen grains (Cherry ring spot),
Insects (Rice Tungro, Potato leaf roll, Papaya mosaic), Nematodes like Xephenema and Longidorus,
Fungi (TNV) and parasitic angiosperms like Cuscuta.
Exclusion of source of Infection, Isolation of source of infection, Eradiacation of Vectors, Chemotherapy
by using Cytovirin-2, Thiouracil, Zinc sulphate and Malachite green and Breeding disease resistant
varieties are the control measures to prevent viral diseases.
Questions from previous exams
1.
2.
Assign the following substances to the cell wall, flagella, ‘S’ layer and Pili of bacteria in correct
sequence. EAMCET - 2008
I. Glycoprotein
II. Fimbrillin
III. Teichoic acid
IV.Flagellin
1) III, I, IV, II
*2) III, IV, I, II
3) II, IV, III, I
4) III, IV, II, I
Study the following and identify the correct match.
EAMCET - 2007
A. Epulopisciumfishelsoni
I. Vector
B. Bacillus thuringiensis
II. Acanthurus
C. Treponema palladium
III. Bacitracin
D. Agrobacterium tumifacience
IV. Bioinsecticide
V. Syphilis
*1) A-II, B-IV, C-V, D-I
2) A-III, B-I, C-II, D-IV 3) A-IV, B-II, C-I, D-III 4) A-IV, B-II,
C-V, D-III
3.
4.
Study the following and identify the correct match.
A. Streptomyces rimosus
I. Cyclomeximide
B. Streptomyces nodosus
II. Neomycin
C, Streptomyces grieseus
III.Oxytetracyclin
D. Streptomyces fradiae
IV. Amphoterican
V. Bacitracin
*1) A-III, B-IV, C-I, D-II
2) A-III, B-I, C-V, D-II
C-III, D-V
EAMCET - 2006
Identify the correct pair of events when termperate Phages infect bacteria
EAMCET - 2009
3) A-I, B-III, C-V, D-IV 4) A-I, B-II,
I. No prophages are formed
II. Bacterial cell undergoes many divisions
III. Bacterial cell undergoes immediate lysis
IV. Prophages are formed
1) I, II
2) II, III
3) III, IV
*4) II, IV
Important questions
1.
Study the following and identify the correct match
A. A chain of spherical cells
I) Bacterium used to clean the ganges waters
B. Singl rod shaped cell
II) Thiomargaritanamibiensis
C. Has no definite shape
III) Treponemapallidum
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D. Monotrichous
IV) Vinegar bacterium
V) Epulopisciumfishelsoni
2) A-III, B-IV, C-I, D-II
4) A-II, B-V, C-III, D-I
1) A-V, B-IV, C-II, D-I
*3) A-II, B-V, C-IV, D-I
2.
3.
[A] : All spirochaetes are spirillae.
[R] : All spirillae are spirochaetes.
1) A and R are correct and R is the correct explanation of A
2) A and R are correct but R is not the correct explanation of A
*3) A is true but R is false
4) A is false but R is true
Study the following
A. N2 → NH3
I) Nitrosomonas
A
B.
NO3−
→ N2
C. NO2− → NO3−
D. NH3 →
4.
NO2−
C
D
II) Nitrobactor
*1)
V
IV
II
I
III) Aquaspirillum
2)
V
IV
II
III
IV) Thiobacillus
3)
IV
V
I
II
4)
V
III
II
I
V) Rhizobium
Study the following and identify the correct groups
I) PLASMID
B
POLYNUCLEOTIDES
HAS
PATHOGENIC
ABILITY
II)
CELL
WALL
SINGLE LAYERED COMPONENTS
PEPTIDOGLYCON HAVE
PATHOGENIC
ABILITY
III)
MESOSOME
IV) SLIME
LIPOPROTEINACEOUS
DNA
REPLICATION
ALWAYS
PREVENTS
HAS
POLYSACCHARIDES
NUTRIENT
LEAKAGE
5.
1) i and iv
2) ii and iii
*3) i and iii
[A] : T2 phage and λ-phage are bacteriophages.
4) ii and iv
[R] : T2 phage has tail sheath but λ is not having tail sheath.
1) A and R are correct and R is the correct explanation of A
*2) A and R are correct but R is not the correct explanation of A
3) A is true but R is false 4) A is false but R is true
6. Study the following and identify the correct match
Disease
Transmitting agent
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A
B
C
D
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A. Bean mosaic disease
I) Nematode
B. Papaya mosaic disease II) Seeds
C. Tobacco necrosis
III) Pollen grains
D. Cherry ring spot
IV) Fungus
V) Insects
1)
2)
3)
*4)
V
II
II
II
II
V
IV
V
I
IV
V
IV
III
I
I
III
7. Arrange the following events of lytic cycle of T4 bacteriophage in correct sequence
i) Role of viral DNA
iii) Function of tail sheath
1) ii, iv, i, iii
2) iv, ii, iii, i
ii) Role of tail fibres
iv) Activity of lysozyme
*3) ii, iv, iii, i
4) ii, i, iii, iv
Crop Improvement
It is also known as plant breeding. It is an applied branch of botany that deals with development of new varieties of crop
plants from the existing varieties by using mainly the methods of Cytogenetics and Molecular genetics.
It has emerged as a science after the rediscovery of Mendals laws.
Selection was the first discovered method and Introduction is second discovered method of crop imporovement.
The methods used for the improvement of a crop are based on the type of reproduction and pollination in the crop.
The various methods that are commonly used are 1. Introduction, 2. Selection, 3. Hybridization, 4. Mutational breeding and 5.
Polyploidy breeding.
Introducing a plant into a new locality from its growing locality is called as Introduction. It is fastest, simplest and easiest
method which does not require any scientific knowledge and skill. Introduced plant serves as Germplasm bank and can be
used directly in Agriculture.
Sonora 63 and 64 Mexican wheat varieties and IR 8 Paddy variety of Philippines are introduced into our country.
Selection is the oldest plant breeding method and basis for crop improvement. It is of 3 types called Mass selection, Pureline
selection and Clonal selection.
Choosing the plants with desirable characters from a mixed population and collecting the seed from them to raise the crop in
the next year is called Mass selection. It has been practiced by farmers. It improves the yield and quality of the crop. It is
applicable to cross pollinated crops and the variety is in heterozygous condition. It takes 8 years for the development of a
variety.
It is the easiest of all selection methods which does not require Scientific knowledge. Dharwar American, Dodahatti local and
Cambodias varieties of cotton and PusaMoti of Bajra are developed by this method.
Developing and choosing the purelines with desirable characters for cultivation is called as Pure line selection. It was first
developed by Johannsen in Phaseolus vulgaris. It is applicable to self pollinated crops. All individuals are phenotypically and
genotypically same and homozygous. It takes 10 years time for the development of a variety.
Ground nut varieties TMV-3, RSB-17 and Paddy varieties CO-4,6,10, 14 are developed by this method.
Developing and choosing desirable clones for cultivation is called as Clonal selection. It is applicable to vegetatively
propagated crops. Individuals of a clone are heterozygous and phenotypically and genotypically same. It takes about 9 years
time for the development of a clone.
Kufri Red, KufriSafed varieties of Potato and MundapaPeddaneelam Mango variety are developed by this method.
Hybridization is cross between genetically unlike parents with desirable characters. It is the most important method which
causes much genetic variability.
Hybridization method has a series of steps that include Selection of Parents, Emasculation, Bagging, Artificial cross
pollination, raising F2 generation plants, Improving and multiplication of F2 generation and distributing the seed to farmers.
By this method several desirable characters can be incorporated into a single variety and usually the hybrids show vigour
which is exploited for the improvement of Crops.
Hybrid vigour is superiority of the hybrid over its parents in having desirable characters. It was first discovered by Kolreuter
and the term Heterosis for this was given by Shull. Presence of more dominant genes and Heterozygosity are the two main
reasons for Hybrid vigour.
Mutations were discovered by Hugo de Vriese in Oenotheralamarkiana. Exploiting desirable mutations for the improvement
of crops is called as Mutationla breeding.
Experiments on Drosophila by Muller and on Barley by Stadler by using X- rays laid foundations for mutational breeding. It
is the quickest method to bring genetic variability in the crop variety.
UV, X, α,β and γ rays are physical mutagens. The chemical mutagens are Colchicine, Formaldehyde, EMS and Maleic
hydrazide.
Disease resisance in IR-8, Winter hardiness in Sweedish variety of Barley and Aruna variety of Castor are developed by
Mutational breeding.
Utilisatiion of Polyploidy for the improvement of crops is called as polyploidy breeding.
Embryos are subjectied to cold treatment and buds of plants to X-rays, Cochicine, Acenaphthene and Coumarins treatment to
induce polyploidy.
Allohexaploid Bread wheat (Triticumaestivum) is developed by this method by using Triticummonococcum,
Aegilopsspeltoides and Aegilopssquarrosa.
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