Class 11th MTG Biology notes, Study notes of Biology

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Page No.

Nature and Scope of Biology vi

• 1. Systematics ♂░▀♀–σ∟–▼▀♠◄☻☼▀♀♦–▒◘–▌▀◘◄– σ–ă–φφ
• 2. Viruses
• 3. Kingdom Monera
• 4. Kingdom Protista
• 5. Fungi, Lichen and Mycorrhiza
• 6. Plant Classification ♂░▀♀–τ–∟–█▀░◙▼▒▐–▓▌○░♀○◄– φ←–ă–↓τ
• 7. Algae
• 8. Bryophyta
• 9. Pteridophyta
• 10. Gymnosperms
• 11. Angiosperms
• 12. Evolutionary Trends & Classification of Animals ♂░▀♀–φ–∟–█▀░◙▼▒▐–○░▀▐○▌▀○– ↓φ–ă–στ↨
• 13. Protozoa
• 14. Non-Chordates
• 15. Chordates
• 16. Tools and Techniques in Cytology ♂░▀♀–←–∟–►◄▌▌–▲▀▒▌▒◙♦– σφε–ă–τσε
• 17. Cell as a Unit of Life
• 18. Biomembrane
• 19. Structural Organization of Cell
• 20. Biomolecules
• 21. Enzymes
• 22. Cellular Metabolism
• 23. Cell Reproduction
• 24. Origin of Life ♂░▀♀–↑–∟–◄♠▒▌♂♀▀▒░– τσσ–ă–τφ↨
• 25. Relationship Among Organisms and Evidences of Evolution
• 26. Theories of Evolution
• 27. Human Evolution
• 28. Plant Taxonomy ♂░▀♀–↓–∟–☼♀☻♂►♀♂☻○▌–○░▼–▒☻◙○░▀☼○♀▀▒░–▀░–▓▌○░♀☼–○░▼–○░▀▐○▌☼– τ←ε–ă–φτε
• 29. Morphology of Flowering Plants
• 30. Anatomy of Flowering Plants
• 31. Animal Tissue
• 32. Integumentary System
• 33. Morphology and Anatomy of Animals (Frog, Cockroach, Rabbit, Earthworm)
• 34. Water Relations of Plants ♂░▀♀–ă–↔–∟–▓▌○░♀–▓Ř♦☼▀▒▌▒◙♦– φτσ–ă–φ↓τ

ŕďőĽę– ĐĽŐńŐĹť vii

Forensic Science Application of scientific knowledge to questions of civil and criminal law (includes use of fingerprints, blood typing, identification of narco tics etc). Surgery Surgery involves physical operations to cure diseases or injuries to the body. Human Reproductive Biology Science of understanding and regulating reproduction. Nutrition Study of the nourishment of human beings or other organisms. Physiotherapy Science of treatment of diseases, bodily weaknesses or defects by physical remedies such as massage and exercise. Occupational Therapy A method of treatment of convalescents and the physically handicapped utilising light work for diversion, physical exercise or vocational training. Genetic Engineering Science that involves manipulations at gene level so as to produce an organism with a new combination of inherited properties. Biomedical Engineering Science for production of spare parts for man, implants, artificial limbs, heart lung machines etc. Food Technology Application of science for processing and preservation of foods. Silviculture Management of useful forest. Olericulture Cultivation of vegetables. Anatomy Internal structures of living organisms. Biochemistry Science connected with chemistry (composition, chemical nature, mode of formation, functioning) of living matter. Biogeography Distribution of organisms on various parts of earth. Cytology Structure and functions of cells and their organelles. Ecology Relationship between organisms and environment. Embryology Development stages of organisms up to hatching or birth. Endocrinology Endocrine glands and hormones. Evolution Origin of life and the gradual differentiation or descent of species. Eugenics Factors related to improvement of human race. Exobiology Life on other planets. Genetics Heredity and variations. Histology Tissues by microscopy. Immunology Resistance of organisms to infection. Limnobiology Fresh water lakes, ponds and streams. Morphology External shape of living organisms in contrast to function. Molecular biology Physiochemical organization of biomolecules. Palaeontology Fossils and their distribution in time. Palaeozoology/Palaeobotany Fossil animals/fossil plants. Physiology Functions of various organs within the organisms. Psychology Behaviour and working of mind. Parasitology Parasitic organisms. Pathology Diseases and their control. Radiobiology Effects of radioactivity on life. Taxonomy Classification of organisms and their evolutionary relationship with other organisms. Teratology Malformation or birth defects. Zoogeography Distribution of animals over the earth. Zoopathology Diseases of animals.

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RELATIONSHIP OF BIOLOGY TO OTHER SCIENCE

In order of study biology one has to understand and know other sciences like physics and chemistry as well. Because our present knowledge of biology has reached to such an extent that it has become a multidisciplinary branch of science involving participation of the fundamental knowledge of all the basic sciences.

Similarly other branches also have relationship with Biology in their particular characters like – l Geography – Required for studying the distribution of organisms. l Climatology – There is an intimate relationship between distribution and adaptations of organisms with the climate of the area. l Geology – Study of palaeobiology and soil types cannot be carried out without the knowledge of geology etc.

UTILITY OF STUDY OF BIOLOGY

The scope and application of biology is quite vast. Its study provides a necessary knowledge and perfect understanding about almost all the spheres of life, its requirements and the various ways by which they can be fulfilled. Study of biology is connected with the following objectives. l To help us to understand ourselves better. It explains the basic concepts like structure and functions of cells, organs and organ systems. It explains about heredity i.e ., why do we resemble our parents and why are we different. It helps us to answer the basic questions about ourselves like what happens during sleep, when we eat food, when we get hurt, and how do we remember things etc. l To help us to meet our needs by utilising the sources available. The knowledge of medicine, surgery, crops rotation, animal husbandry help us to cure diseases and improve the quality of plants and animals. Meeting our basic requirements of food, clothing and shelter. l To acquaint us with the fundamentals of nutrition, health and population control. To have a scientific approach while solving problems. l To enlighten us about our place in the universe. It helps us to understand that man is only a small part of the living system and we have a responsibility to protect and respect other living things on earth.

Structure/ Mechanism Studied Cell membrane

Transportation of O 2 in body Excretory system

Absorption of food/water

Transportation of water in plants

Release of energy during respiration Effect of light on flowering

Example

Structure of lipids, and proteins Formation of oxyhaemoglobin Absorption and elimination of salts Absorption of sugars amino acids, fatty acids, water or salts Conduction of water from root to leaves

Electron transport chain Absorption of different wave lengths of light

Related Science

Chemistry

Chemistry

Chemistry

Chemistry

Physics

Chemistry

Physics

Knowledge of other sciences is required because

Living organisms are made up of inorganic and organic compounds. All metabolic pathways involve chemical changes.

Homeostasis involves acidbase equilibrium to maintain pH of living organism. During diffusion and osmosis molecules move in and out of cells.

Liquids have certain properties like cohesion and adhesion that result in surface tension and capillary action which help in certain processes. Energy transfer and transformation are important in all the living cells. Light induces definite pattern of responses in plants and animals.

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Some of the examples of serendipity are – ‹ Discovery of antibiotic – Penicillin : Alexander Fleming (18811955) was culturing the bacterium – Staphylococcus (the causal organism infection) in Petri dishes on agar medium. He found that one of his culture plate was contaminated by bluegreen mould – Penicillium notatum. Such a contamination in laboratories was not new. Normally such contaminated cultures are discarded but Fleming retained it and observed minutely. To his surprise, he noticed that fungal growth inhibited in those areas where fungus was growing. By flash idea Fleming poured the extract of fungus over fresh bacterial cultures and found that even the extract inhibited the bacterial growth. This curious observation led the discovery of the most important antibiotic

- Penicillin. ‹ Law of Gravitation : Newton was simply sitting in the garden when an apple fell on the ground. He started thinking about the cause of its fall and came to a conclusion that some force is present in the earth which attracts everything towards it. This observation led the formation of Newton’s law of gravitation. ‹ Structure of Benzene ring : Chance observation of snake licking its tail led the discovery of ring – structure of benzene by Kekule. ‹ Archimede’s Principle : While taking bath he came to the conclusion that a body which is immersed partially or completely in a liquid, experiences an up thrust equal to the weight of the liquid displaced by it. This led to the discovery of principle of floatation by Archimedes.

Antibiotics Alexander Fleming (

Ayurveda Charaka Bacteriology Antony Van Leeuwenhoek (16321723) Biochemical genetics Archibald Garrod Biochemistry Justus vol Liebig (180373) Biology Aristotle (384322 BC) Blood circulation William Harvey (15781657) Blood groups Karl Landsteiner Botany Theophrastus (372287 BC) Chromatography Micheal Tswett Comparative anatomy Georges Cuvier (17691832) Cytology Robert Hooke (16351703) ECG Einthoven Ecology Theophrastus (370285 BC) Embryology Aristotle Endocrinology Thomas Addison (17931860) Eugenics Francis Galton Experimental genetics Thomas Hunt Morgan (

Gene Therapy Anderson Genetic engineering Paul Berg Genetics Gregor Johann Mendel (18221884)

Histology Xavier Bichat (17711802) Homeopathy Hahnemann (17551843) Immunology Edward Jenner Indian palaeobotany Birbal Sahni (18911949) Medicine Hippocrates (460377 BC) Microbiology Antony Van Leeuwenhoek Microbiology Louis Pasteur (18221895) Microscopic Anatomy Marcello Malpighi (

Microscopy Antony Van Leeuwenhoek Modern embryology Von Baer (17921876) Modern genetics William Bateson (

Modern palaeontology Georges Cuvier (17691832) Palaeontology Leonardo da Vinci Parasitology Platter Protozoology Antony Van Leeuwenhoek Science Aristotle Surgery Susruta Taxonomy Carolus Linnaeus (

Tissue culture Harrison Virology Wendell M. Stanley Zoology Aristotle

Table : Fathers of Biology

nn

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l Systematics is the study of the historical relationships of groups of biological organisms

• the recognition and understanding of biodiversity. l The term systematics was coined by Linnaeus ( 1735 ). l The terms systematics, taxonomy and classification are often held as synonyms but technically they carry different meanings. l G. Simpson (1961) has distinguished the three terms. l Taxonomy is the branch of study which deals with identification, nomenclature and classification of organisms. l Term taxonomy was first given by French botanist A.P. de Candolle (17781841) for the theory of plant classification. l Taxonomy is also called systematic botany. l Carolus Linnaeus is called father of taxonomy. l H. Santapau is called the father of Indian taxonomy. l Taxonomy is of three types – alpha ( a ) taxonomy, beta ( b ) taxonomy and omega ( w ) taxonomy. l When only morphological characters are used for identification and classification of plants then it is called alpha taxonomy. l btaxonomy involves genetical, anatomical cytological, palynological, physiological and other characters. l btaxonomy is also called biosystematics. l a and b taxonomy terms were given by Turill. l Analysis and synthesis of all information and types of data to develop classification system based on phylogenetic relationships is called omega taxonomy. l Classification is the placing of an organism or a

Chapter 1

Systematics

group of organisms in category according to a particular system and in conformity with a nomenclature system. l Aristotle (father of zoology) made the first recorded attempt to classify the animals in his book Historia Animalium. l Aristotle made two main groups anaima (animals with no RBC, invertebrates) and enaima (animals with RBC, vertebrates). l Theophrastus (372 287 BC), referred to as father of botany , classified plants on the basis of form and texture and described 480 plants in his book Historia Planatarum. l Identification is to determine the exact place or position of an organism in the set plan of classification. Identification is carried out with the help of taxonomic keys. l A key provides a convenient way for easy identification of an organism by applying diagnostic or distinguishing characters. l Taxonomy discovers and describes new species , w hile s ys tematics use s evolutionar y relationships to understand biogeography, coevolution, adaptation and options for biological conservation. l Systematists or taxonomists are thus the scientists whose expertise provides the data about the identification, description, distribution and relationship of life on Earth. l New systematics or biosystematics is concept of systematics which brings about taxonomic affinity on the basis of evolutionary genetic and morphological traits. l Julian Huxley (1940) proposed the term new systematics.

☼ťřŚĚŇĘř^3

letters & specific epithet starts with small letter.

• Both these name must be underlined separately (if handwritten) or italised (if printed).
• No comma, hyphen etc. between specific and generic name is used.
• To the two word, name is appended the name of taxonomist who discovered the organism and provided with a scientific name, e.g., Ficus bengalensis L , Homo sapiens L.
• The different names given to same species by different workers are called synonyms , but the name given first is considered to be valid. l The foundations of International Code of Botanical Nomenclature (ICBN) was found in Philosophia Botanica , a book written by C. Linnaeus. Current code of botanical nomenclature appeared in 1978. l Botanical nomenclature is independent of zoological and bacteriological nomenclature which are governed by their own code.

l A specimen or other element selected from the original material cited by the author when no holotype was originally selected or when it no longer exists is called lectotype. l A lectotype is selected from isotypes, paratypes or syntypes. l A specimen or illustration selected to serve as nomenclatural types as long as all of the material on which the name of the taxon was based is missing is called neotype. l Epitype is a specimen or illustration selected to serve as an interpretative type when the holotype, lectotype or previously designated neotype, or all original material associated with a validly published name is demonstrably ambiguous and cannot be critically identified for purposes of the precise application of the name of a taxon. l Topotype is often the name given to a specimen collected from the same locality from which the holotype was originally collected. l When many names are given to the same species, then the name under which the species was first described is valid , provided the publication is effective and valid.

Taxonomic hierarchy or Linnaean hierarchy

l Taxonomic hierarchy is the sequence of arrangements of taxonomic categories in a descending order during the classification of an organism. l The word taxa represents taxonomic groups of any rank i.e. any unit of classification. l In Linnaean hierarchy, the number of taxa is five , namely – class, order, genus, species and variety. l The rank of species is basic and relative order of the rank of taxa are species, genus, tribe, family, order, series, class, division (= phylum ) and kingdom. l These categories/rank are ranked one over the other called ‘hierarchy’. l Kingdom is the highest and species is the lowest category in this hierarchy. l Species is the basic unit of taxonomy. l John Ray introduced the term animal species. l Species inhabiting the same geographical area (identical or overlapping) are sympatric. l Species inhabiting different geographical areas are allopatric.

Some important abbreviation ICBN – International code of botanical nomenclature ICZN – International code of zoological nomenclature ICBacN – International code of bacteriological nomenclature ICVN – International code of viral nomenclature ICNCP – International code of nomenclature for cultivation plants

Types of specification

l The particular illustration designed by author of the species to represent the type of species is called holotype. l A specimen which is a duplicate of the holotype, collected from the same place, same time and by the same person is called isotype. l Any one of the two or more specimens cited by the author when no holotype was designated, or any one of the two or more specimens simultaneously designated as types is called syntype. l A paratype is a specimen cited in the protologue that is neither the holotype nor an isotype, nor one of the syntypes if two or more specimens were simultaneously designated as types.

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l Related species which are reproductively isolated but morphologically similar are called sibling species. l A species restricted to a given area is called endemic species. l Classical systematics is based on the ‘typological concept’ by Plato and Aristotle. l The traditional concept of species was given by Linnaeus in Systema Naturae ; this is based on morphology, and is also known as ‘morphological concept’. l Genetic species concept was given by Lotsy (1918), according to which, a species is a group of genetically identical individuals. l Species that contain two or more subspecies are called polytypic species. l Species that are not subdivided into subspecies are called monotypic species. l Modern concept of species is biological species concept introduced by Ernst Mayr (1942). l Mayr defined species as groups of interbreeding natural populations that are reproductively isolated from each other group. l Genus is an assembly of related species which evolved from a common ancestor and have certain common characters called correlated characters, e.g., Solanum tuberosum and Solanum melongena are two species which belong to same genus of Solanum. l A family subdivision of an order consists of a group of closely related genera, which in turn are composed of groups of closely related species. l The taxon commonly encountered in routine taxonomic work is the family. l Family with a single genus is called monogeneric family. l An order is a category within a class. Carnivora is an order of flesheating animals within the class mammalia and there are several other orders of mammals like cattle, rodents, bats, seals, whales, etc. l A class is a subdivision within a phylum made of one or more related orders, for e.g. , within the phylum chordata there are five classes: mammals, birds, reptiles, amphibians and fishes. l Georges Leopold Cuvier (17691832), the French naturalist, added the ‘ phylum ’ in taxonomy. l In taxonomy, the correct sequence is: class order family tribe genus species.

l Microbiologists and botanists (Eichler) use the term ‘ division ’ instead of ‘phylum ’. l All kingdoms have more than one phylum. l The kingdom plantae contains several divisions (=phyla), including flowering plants, conifer trees, mosses, ferns and several other groups. l Taxonomic hierarchy is useful in that it provides information about relationships of an organism with others quick identification of a taxon , all major traits and nonrepetition of correlated traits of various categories. l According to ICBN different ranks or categories have following specific ‘ endings ’ ( Refer table given below ). Ranks Division/ Phylum Subdivision/ subphylum Class Subclass Superorder Order Suborder Infraorder Superfamily Family Subfamily Tribe Subtribe

Plants Algae phyta

phytina

opsida phyceae idae phycidae

Fungi mycota

mycotina

mycetes mycetidae

Animal

anae ales ineae aria acea aceae ordeae eae inae

oidea idae inae ini ina

Rank Domain Kingdom Phylum or Division Subphylum or Subdivision Class Subclass Order Suborder Family Subfamily Genus Species

Human Eukarya Animalia Chordata Vertebrata

Mammalia Placentalia Primates Haplorrhini Hominidae Homininae Homo H. sapiens

Pea Eukarya Plantae Magnoliophyta Magnoliophytina

Magnoliopsida Magnoliidae Fabales Fabineae Fabaceae Faboideae Pisum P. sativum

Table : Taxonomic status of human & pea

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l Organisms are classified according to two, three, four, five and six kingdom system ( Ref er flowchart ). l The major criteria used for delimitation of kingdoms are modes of nutrition, presence or absence of locomotion, complexity of organisation, and cell structure. l Viruses do not fit neatly into any classification of living organisms because they have a very simple noncellular structure and cannot exist independently of other organisms. l Herbarium is a collection of plant parts that usually have been dried, pressed, preserved on sheets. l Largest herbarium of the world is at Kew. l Botanical gardens are the collections of living plants maintained for reference. l The largest botanical garden is the Main

System of classification

Four Kingdom

Copeland

[Proposed by , (1956)]

Two Kingdom

Monera (all prokaryotic organism)

Protista (Not approved as fungi and (for unicellular organisms) organisms like etc. were not justified in these two kingdoms).

Euglena, Chlamydomonas

Monera (all plants) Plant (all plants) Animal (all animals)

Protista (unicellular eukaryotes) Archaebacteria

Five Kingdom

R.H. Whittaker

[Proposed by , (1969)] Used three criteria

• Complexity of cell structure
• Complexity of body structure
• Mode of nutrition

Plant Kingdom Animal Kingdom

Three Kingdom

Haeckel

[Proposed by , (1866)] Plant Animal Protista (for unicellular organisms)

Eubacteria

Plantae (nonmobile and photosynthetic organisms)

Animalia (Metazoa) Algae Bryophyte Pteridophyte Gymnosperms Angiosperms

Photosynthetic Consumer Protozoa

(eukaryotic, heterotrophic organisms)

Divided into

Botanical Garden, Moscow covering an area of 900 acres. l The Royal Botanical Garden, Kew England covers an area of 300 acres. l Indian Botanical garden, Sibpur, Kolkata , is the largest botanical garden in India. l The collection of plants and animals are preserved and kept in museums for study and reference. l Zoological parks are zoos which help to study wild animals and their food habits. l Camerarius was the person who first recognised sexuality in plants. l If the generic and specific names are same it is called tautonym. But tautonyms have been rejected by modern scientists. l Angiosperms are the most advanced type of plants. l Angiosperms contain seeds enclosed in fruits.

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l The term ‘ Virus ’ has been derived from Latin, which means poison or venom or viscous fluid. l Viruses are defined as infectious nucleoproteins. l Virus are obligate intracellular parasite which can reproduce only by invading and taking over other cells as they lack the cellular machinery for self reproduction.

Chapter 2

l A complete virus particle is called virion whose main function is to deliver its DNA or RNA genome into the host cell. So that genome can expressed (transcribed and translated) by the host cells.

Characteristic features

l These are submicroscopic organisms generally less than 200 mm. Important inventions ÿ Viruses were discovered after Chamberland developed bacterial filters (1884). ÿ Meyer ( 1886 ) describe tobacco mosaic disease but he couldn’t isolate the causal organism. Further, he said that the disease is transmissible and infectious. ÿ Russian botanist D. Ivanowski (1892), discovered the causal organisms of tobacco mosaic disease and this causal organisms could pass through the filters which retained bacteria. ÿ Beijerinck (1898) confirmed the earliest studies and named these organisms as “ Contagium vivum fluidum ”, living infectious fluid. ÿ F.W.T’wort. (1915) and F.H.d’Herelle (1917) discovered certain viruses which infect bacteria or bacteria eaters i.e. , bacteriophages or phages. ÿ Stanley ( 1935 ) crystallized tobacco mosaic virus and said that these crystals retain their infectivity for a long time if kept in bottles. ÿ Bawden and Pirie ( 1936 ) first of all studied the chemical nature of viruses and said that these are nucleoproteins. ÿ Edward Jenner ( 1796 ) discovered vaccination against small pox ÿ Louis Pasteur ( 1880 ) discovered vaccination against rabies ÿ Loeffler and Frosch ( 1898 ) discovered first animal pathogenic virus (Foot and mouth virus of cattle). ÿ S. Luria , M. Delbruck and Lwoff ( 1942 48 ) discovered mechanism of replication in bacteriophages. ÿ A. Harshey and M. Chase ( 1952 ) said that nucleic acids are infective and proteins are noninfective parts of a bacteriophages. ÿ T. O. Diener ( 1971 ) discovered some new infectious agents, which are still smaller than viruses. ÿ Stanley B. Prusiner discovered certain infectious agents or slow viruses which contain only proteins. Prusiner got Nobel prize for this work in 1997. ÿ Alliac Issacs and Lindeman (1957) gave the term interferons to the chemical substances responsible for viral interference. ÿ Mycophages, viruses infecting fungi, were discovered by Sinden ( 1957 ) in Agaricus bisporus. These are having double stranded RNA and are spherical or polygonal in shape. ÿ A. Salk ( 1957 ) invented vaccination against Polio ÿ Lu Montagnier et. al. (1893); R. Gallo et. al. (1984) discovered AIDS virus for HIV. ÿ Safferman and Morris ( 1963 ) discovered cyanophages (viruses infecting cyanobacteria like Lynggya).

Viruses

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l It is a rod shaped virus measuring 300 × 18 nm and have helical symmetry. l Have single stranded DNA which is 330 nm in length and having 7300 nucleotides. l Number of capsomeres in capsid is 2130. l 5% RNA and 95% protein is present in TMV.

Bacteriophages

l Viruses infecting bacteria are known as bacteriophages or phages. Sea water can hold 100 million bacteriophages per μl. l Bacteriophages may be virulent or avirulent. l Prophages or nonvirulent phages or non infective phages are the phages which do not cause lysis of bacteria soon after their formation inside. Such bacterial cells which are having prophages inside them are called lysogenic bacteria. l Virulent phages or infective phages are the phages which cause lysis of bacterial cell at once. l Most studied series of bacteriophages is Tseries (T 2 , T 4 , T 6 etc.). l Teven phages are characterized by angular head and contractile tail. l Bacteriophages have tadpole like structure, i.e ., with head and tail. Inside the head is present nucleic acid , generally DNA. l Head is prism like hexagonal having length 950Å and breadth 650Å, tail is also 950Å in length, joined to head by neck and collar, tail is having hollow core of 80Å and is surrounded by tail sheath. l At the end of tail, end plate is present to which 6 tail fibres are attached and each is 1500Å in length. Lytic cycle (T 4 bacteriophage) l The multiplication process of virulent phage is called lytic cycle. l The main steps include adsorption , penetration , formation of new phages and lysis. l Bacteriophage attaches to the surface of bacterium by its tail fibres. l Lysozymes creates a hole in the host cell wall. l The tail sheath contracts and ejects the viral chromosome/DNA into the bacterium. l Viral DNA controls the metabolic machinery of the host cell. It produces nucleases. l Nucleases degrade DNA and mRNAs of the host. l Viral DNA is not affected as its cytosine bases are methylated. l A number of copies of viral DNA are produced

followed by synthesis of capsid protein, polyamines and lysozymes. l The components assemble and form phage particles or viruses. l The host cell ruptures to release viruses ( lysis ). Lysogenic cycle (l phage) l The multiplication process of temperate phage is called lysogenic cycle. l The phenomenon of existence of nonvirulent prophage in the host cell is called lysogeny. l The host cell in which lysogeny occurs is called lysogenic cell. l Lysogen is a strain of bacteria carrying prophage. l Lysogenic cycle is shown by 1 (lambda) phage which also infects E.coli bacterium. l Lytic bacteriophage multiply in host bacterium which then undergoes complete lysis (degeneration) to release the resulting daughter phages. l The phage attaches to the surface of bacteria by means of tail, which produces a hole in host cell wall and injects the phage DNA. l Phage DNA produces a repressor, (C1) becomes nonvirulent or temperate and gets integrated to bacterial chromosome at a specific site by means of enzyme integrase. l The viral genome is now called prophage/provirus. l It multiplies alongwith bacterial genome and is passed on to the progeny. l Occassionally the synthesis of repressor is stopped due to ultra violet radiations or chemical factors. l The temperate/nonvirulent phage is now changed to lytic/virulent phage. l The single strand DNA of f × 174 or coliphage fd is known as plus strand. It forms its complementary or negative strand. The double strand or replicative DNA takes over the metabolic machinery of host to synthesize plus strands DNAs and protein for assembly of new phages. Pinocytic reproduction l The whole virus enters the host cell except the envelope. It is quite common in RNA viruses which are of two types as RNARNA virus and RNADNA virus. l In RNARNA viruses DNA has no role in their multiplication. After entering the host cell the viruses produce enzyme replicase which helps in producing more genetic RNA over the template

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of parent RNA genome. The latter also produces m RNAs for synthesis of viral proteins. l RNADNA viruses are also called retroviruses (Temin, 1970), e.g. , Tumor/Cancer viruses, HIV. The virus es pos sess enzyme reve rs e transcriptase (Temin and Baltimore, 1972; in Rous Sarcoma Virus or RSV of Mouse). The enzyme builds DNA over RNA genome. The phenomenon is called reverse transcription or teminism. l The copy DNA (cDNA) builds its complementary strand. The double strand copy DNA attaches to host DNA/chromosome and is now called provirus. l Application of bacteriophages are –

• Studying viral infection mechanism.
• Control of certain bacterial diseases.
• Purity of Holy Ganges is due to presence of bacteriophages. Viroids are subviral infectious agents, which contains only very low molecular weight RNA and not protein coat. Viroids cause potato spindle tuber disease (PSTV), citrus exocortis etc. The only human disease known to be caused by a viroids is hepatitis D. Interferons are protein molecules which prevent viral multiplication. These are produced by cells in mammals, rodents, birds, etc. and provide resistance against viruses.

Diseases caused by viruses

l Virus causes diseases in plants, animals and human brings. l Plant diseases caused by viruses are –

• Tobacco mosaic disease
• Leaf curl of papaya
• Yellow vein mosaic of bhindi
• Potato leaf roll
• Vein bandings mosaic disease of potato
• Grassy shoot of sugar cane
  • Bunchy top of banana
  • Tungro disease of rice
  • Tomato leaf curl l Human diseases caused by viruses are – Chicken pox : Varicella virus Small pox : Variola virus Measles : Rubeola virus Rabies : ssRNA ( Rabies virus Lassa virus ) AIDS : ARV ( Aids associated retrovirus ) Yellow fever : Transmitted by Aedes aegypti mosquito Dengue fever : Transmitted by Aedes aegypti mosquito Polio : Transmitted through food, water, contact HepatitisB : Transmitted through contact and body fluid. l Transmission of viruses occurs by –
• Polluted air, water and food stuffs help the dissemination of viruses in man and animals.
• Fly and mosquitoes usually act as carriers.
• Such virus transmitting agents are called vectors.
• Most of the virus diseases of plants are transmitted through insects.
• Sap sucking insects like aphids and white flys are the important ones among such vectors.
• Virus diseases are also transmitted through stem cuttings, seeds, tubers, agricultural implements etc. l Disease can be controlled by –
• Removal of diseased plants and plants parts.
• Using disinfested seed.
• Testing the germplasm and selecting virus free seed.
• Destruction of alternative hosts.
• Destruction of insect vectors.
• Practising crop rotation.
• Growing disease resistant varieties.

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l Bacteria possess a distinct cell wall, with different wall layers like capsule or slime layer, plasma membranes, flagella and pilli. l Slime layer or capsule is made up of polysaccharides and amino acids and acts as osmotic barrier. l Cell wall is made up of polysaccharides , proteins and lipids and peptidoglycan or murein. l Plasma membrane is tripartite in nature. l Mesosomes are simple infolding of plasma membrane containing respiratory enzymes, like oxidases and dehydrogenase. l Flagella is made up of flagellin. l Pili are small hair like outgrowth present on bacterial cell surface made up of pilin protein. l Pilin helps in formation of conjugation tube and agglutination. l Based on the nature of staining , bacteria may be Gram + ve (retains the blue stain) or Gram –ve (does not retain the stain). Gram staining Heat fixed smear of bacteria Crystal violet

Rinse with water Add dilute iodine solution

All bacterial cell appears deep blue

Treat with 95% alcohol

Cells retain purple colour Gram +ve bacteria

Destained and appear red in colour Gram –ve bacteria l Inner to the wall layers, there is present matrix or protoplasm which includes nucleoid , plasma , episomes , ribosomes , and granules. l In the centre of the bacterial cell, there is present nuclear material (DNA) without any nuclear membrane (naked). DNA in bacteria is double helical and circular. l This incipient nucleus or primitive nucleus is named as nucleoid or genophore (sometimes called single naked chromosome). l Besides this nuclear DNA, there is some extranuclear or extrachromosomal DNA, which is known as plasmid.

Table : Difference in the cell walls of gram +ve & gram –ve bacteria Gram +ve bacteria

1. Cell wall more thick, thickness varies from 2530 nm.
2. Cell wall is a homogenous layer.
3. High content of peptidoglycan (2080% of the dry weight of the cell).
4. Teichoic acids may be present.
5. Very little lipid content (02%).
6. Only a few aminoacids are associated with the muramic acid complex.
7. Lipopolysa ccha ride layer (LPS) absent.
8. Periplasmic space is absent.

Gram –ve bacteria Cell wall thin.Thickness varies 1015 nm.

Three layered.

Less content of peptidoglycan (1020% of the dry weight of the cell).

Teichoic acids absent.

High lipid content ( 20%). Large variety of aminoacids are associated.

Present.

Present.

l The plasmid are small , circular , double stranded DNA molecules that are separate from ma in bacteria l chromosome and replica te independently. l The term plasmid was given by Lederberg ( 1952 ). l Plasmids have an independent existence. l Plasmids carry genes for fertility , antibiotic resistance ( Rfactor ) and bacterium ( Colicin ) production ( colicinogenic factor ). l Ffactor or fertility factor is responsible for transfer of genetic material. l Rfactor or resistance factor provides resistance against drugs. l Colicinogenic factor produces ‘ colicines ’ which kill other bacteria (other than which produces these colicines). l The term episome is applied to extranuclear genetic material which may remain in integrated or free state, e.g., Ffactor, temperate phage, etc. l Ribosomes are evenly distributed in the matrix. Ribosomes are of 70S type (50S + 30S). l Ribosome are the seat of protein synthesis and are made up of rRNA and protein.

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l There are present different types of granules like volutin granules, fatty acid granules (lipid granules), glycogen and sulphur granules. l According to the mode of respiration , bacteria can be aerobic or anaerobic. Each of them is further of two types, obligate and facultative. l Obligate aerobes are bacteria which can respire only aerobically. They generally get killed under anaerobic mode of respiration, e.g., Bacillus subtilis. l Facultative aerobes are bacteria which respire anaerobically under normal conditions but can respire aerobically when oxygen is available. Most of the photosynthetic bacteria belong to this group. l Obligate anaerobes are bacteria that respire only anaerobically. They generally get killed under aerobic condition, e.g., Clostridium botulinum. l Facultative anaerobes are bacteria which generally respire only aerobically but switch over to anaerobic mode of respiration if oxygen becomes deficient.

Nutrition

l Bacteria show both autotrophic and heterotrophic nutrition. l Autotrophic nutrition consists of manufacture of organic materials from inorganic raw materials with the help of energy obtained from outside sources. It is of two types – chemosynthesis and photosynthesis. l The bacteria possess photosynthetic pigments of two types, bacteriochlorophyll and bacteriophaeophytin (chlorobium chlorophyll). The two types of pigments respectively occur in purple bacteria (e.g., Thiopedia rosea, Rhodopseudomonas ) in membranes of thylakoids. l No oxygen is evolved in bacterial photosynthesis. Such type of photosynthesis is known as anoxygenic photosynthesis. l Water is not used as a source of reducing power. Instead, hydrogen is obtained either directly (some purple bacteria) or from various types of inorganic and organic compounds, e.g. , H 2 S (green bacteria), aliphatic compounds (purple nonsulphur bacteria). l Chemoautotrophic bacteria are bacteria which are able to manufacture their organic food from inorganic raw materials with the help of energy derived from exergonic chemical reactions involving oxidation of an inorganic substance present in the external medium. They are of various types.

l Nitrifying bacteria , Nitrosomonas and Nitrosococcus obtain energy by oxidising ammonia to nitrite. NH 4 +^ + 2O 2 Æ NO 2 –^ + 2H 2 O + Energy Nitrocystis and Nitrobacter oxidise nitrites to nitrates. 2NO 2 –^ + O 2 Æ 2NO 3 –^ + Energy l Sulphur oxidising bacteria , Beggiatoa , a colourless sulphur bacterium, oxidises hydrogen sulphide to sulphur in order to obtain energy for chemosynthesis. Beggiatoa 2 H S+ O 2 2 æææææÆ2S+ 2 H O+ Energy 2 Thiobacillus thioxidans , another sulphur bacterium, oxidises sulphur to sulphate state. Beggiatoa 2S+ 2 H O + 3O 2 2 ææææThioxidansæÆ (^) 2H 2 SO 4 + Energy l Iron bacteria , Ferrobacillus ferrooxidans obtains energy by oxidising ferrous compounds to ferric forms. 4FeCO 3 + 6H 2 O + O 2 Æ 4Fe(OH) 3 + 4CO 2 + Energy l Other chemosynthetic bacteria, bacterium Methanomonas oxidises methane into CO 2 and H 2 O. CH 2 + 2O 2 Æ CO 2 + 2H 2 O + Energy l Heterotrophic bacteria may be saprophytic , parasitic or , symbiotic. l Saprophytic are living bacteria which obtain their food from organic remains , e.g. , corpses, animal excreta, fallen leaves, vegetables, fruits, meat, jams, jellies, bread and other products of plant and animal origin. l Symbiotic bacteria live in mutually beneficial association with other organisms. Enteric bacterium Escherichia coli , live as a symbiont in human intestine. l Parasitic bacteria , live in contact with other living beings for obtaining nourishment or special organic compounds required for growth (growth factors). l Bacteria show four major phases of growth in a fresh nutrient rich medium – (i) lag phase , (ii) log phase (logarithmic or exponential phase), (iii) stationary phase , and (iv) decline phase (death phase). These phases constitute the standard bacterial growth curve.

Reproduction

l Bacteria show 3 methods of reproduction – vegetation reproduction , asexual reproduction , sexual reproduction.

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