# Current Affairs 11th Class

#### Importance of bacteria

Bacteria are our ‘friends and foes’ as they have both useful and harmful activities. Useful activities (1) In agriculture or In soil fertility : Some bacteria increase soil fertility. Nitrogen is essential for all plants. Nitrogen occupies 80% of the atmosphere. The plants take nitrogen in the form of nitrates. In soil, nitrates are formed by three processes : By nitrogen fixing bacteria : Bacteria are found in soil either free e.g., Azotobacter and Clostridium or in root nodules of leguminous plants e.g., Rhizobium leguminosarum. These bacteria are capable of converting atmospheric free nitrogen into nitrogenous compounds. Nitrifying bacteria : These bacteria convert nitrogen of ammonia into nitrite (NO2) e.g., nitrosomonas and convert nitrite compounds into nitrates e.g., nitrobacter. Decay of dead plants and animals : Some bacteria attack on dead bodies of plants and animals and convert their complex compounds into simpler substances e.g., carbon dioxide (CO2), water (H2O), nitrate (NO3), sulphate (SO4) etc. (2) In dairy : Bacterium lactici acidi and B. acidi lactici are found in milk. These bacteria ferment lactose sugar found in milk to form lactic acid by which milk becomes sour. Lactic acid bacteria bring together droplets of casein a protein found in milk and help in the formation of curd. On freezing of casein of milk protein it is fermented by bacteria with the result that foamy and soft substance, different in taste is formed. (3) In industries : From industrial point of view bacteria are most important. Some of the uses of bacteria in industries are as follows : Vinegar industry : Vinegar is manufactured from sugar solution in the presence of Acetobacter aceti. Alcohol and acetone : Clostridium acetobutylicum takes part in the manufacture of butyl alcohol and acetone. Fibre retting : By this process fibres of jute, hemp and flax are prepared. In the preparation of flax, hemp and jute the retting of stems of Linum usitatissimum (Flax = Hindi Sunn), Cannabis sativa (Hemp = Hindi Patson) and Corchorus capsularis (Jute) respectively is done. Tobacco industry : Bacillus megatherium is used for its fermentative capacity for developing flavour and taste in tobacco leaves. Tea industry : By fermentative action of Mycococcus condisans curing of tea leaves is done. By this process special taste is developed in the tea leaves. Tanning of leather : Some bacteria decompose fats which are found in skin of animal with the result that skin and hairs are separated from each other and this leather becomes ready for use. Disposal of sewage : Some bacteria convert organic faecal substances e.g., cow dung, decaying leaves of plants, etc. into manure and humus. Human symbionts : Escherichia coli inhabitats the large intestine of man and other animals and it synthesizes vitamins. (4) In medicines : Some of the antibiotics are manufactured by bacterial actions e.g., Bacillus brevis – antibiotic thyrothricin and B. subtilis – antibiotic subtelin. Vitamin B2 is manufactured by fermentative action of Clostridium acetobutylicum. Antibiotics : These are the chemical substances produces by living microorganisms capable more...

#### Economic Importance of Cyanobacteria

Cyanobacteria have both beneficial and harmful effects in human affairs. Useful activities (1) Growth of cyanobacteria in hard water is most probably responsible for the deposit of limestones. (2) Since they grow, photosynthesis, multiply and ultimately die, thus adding organic matter to the soil and increasing its fertility. (3) Whereas some cyanobacteria act to breakdown rock, the species that live in hot springs actually build rocks. This they accomplish by depositing salts of calcium and silica within the gelatinous sheath of the algal cell wall. (4) Balls of Nostoc commune are collected, boiled and consumed as food by the Chinese and South Americans. The prepared food is called 'Yoyucho'. (5) Some cyanobacteria, such as Anabaena, Lyngbya etc. help in conservation of soil, thus checking soil erosion. (6) Few species of Anabaena and Aulosira are inoculated in ponds to check the development of mosquito larvae. (7) Certain cyanobacteria like Nostoc commune, Scytonema ocellantum, Aulosira fertissima are used for reclamation of usar (sterile alkaline) soil. Harmful activities (1) Their most harmful effect is undoubtedly the formation of blooms in bodies of water. (2) They choke the intake of water supply systems and give the water a disagreeable odour giving a fishy taste to drinking water. (3) Many cyanobacteria produce toxins. They are directly or indirectly harmful for human. e.g., Nostoc, Anabaena, Microcystes etc. Habitat : Nostoc is found in aquatic and terrestrial habitat. The alga forms a jelly like mass in which numerous filaments are embedded. When young, they are more or less spherical, solid and microscopic in size. With advance in age, the colony grows and becomes macroscopic. In species like N. amplissimum it attains the diameter of 30cm or almost equals to the size of hen's egg in N. punctiforme. A number of species of Nostoc on soil. They often swell up and glisten after rains and therefore called fallen stars. Morphology : The plant is filamentous and trichome are unbranched and appear moniliform.. All the cells of the trichome are similar in structure but at intervals are found slightly larger rounded, light yellowish, thick walled cells called as heterocysts. Trichome mostly breaks near heterocyst and forms harmogonia and thus they help in its multiplication. The heterocysts are intercalary and possess a very thick outer wall. Each heterocyst is connected with vegetative cells on two sides through prominent pores in the wall which later are occupied by a refractive cyanophycean granule called polar nodule. Each cell trichome in Nostoc has primitive nucleus and chromoplasm and very much resembles in all details to a cyanophycean cell. Vacuoles and definite chromatophores are absent. The cellwall is differentiated into two layers. Outside the cellwall there is a mucilaginous sheath. Due to confluence of various mucilaginous sheaths of filaments, a mucilaginous colony is formed. The cell is prokaryotic. Reproduction in Nostoc There is no sexual reproduction more...

#### Economic importance

(1) Many species of Nostoc fix atmospheric nitrogen and thus increases soil fertility. (2) Reclamation of alkaline usar soils can be done by employing some species of Nostoc. (3) N. commune is consumed as vegetable in China and Japan.

#### Characteristics of Monera

Monera (Monos – single) includes prokaryotes and shows the following characters : (1) They are typically unicellular organisms (but one group is mycelial). (2) The genetic material is naked circular DNA, not enclose by nuclear envelope. (3) Ribosomes and simple chromatophores are the only subcellular organelles in the cytoplasm. The ribosomes are 70 S. Mitochondria, plastids, golgi apparatus, lysosomes, endoplasmic reticulum, centrosome, etc., are lacking. (4) Sap vacuoles do not occur. Instead, gas vacuole may be present. (5) The predominant mode of nutrition is absorptive but some groups are photosynthetic (holophytic) and chemosynthetic. (6) The organisms are non-motile or move by beating of simple flagella or by gliding. (7) Flagella, if present, are composed of many intertwined chains of a protein flagellin. They are not enclosed by any membrane and grow at the tip. (8) Moneran cells are microscopic (1 to few microns in length). (9) Most organisms bear a rigid cell wall (Peptidoglycan). (10) Reproduction is primarily asexual by binary fission or budding. Mitotic apparatus is not formed during cell division. (11) The kingdom Monera includes true bacteria, mycoplasma, rickettsias, actinomycetes (ray fungi) etc. Microbiologists also include blue green algae (i.e., Cyanobacteria) under the group bacteria because of the presence of prokaryotic cell structure. Studies have established that the members of archaebacteria group are most primitive and have separated from eubacteria group very early in the process of evolution.      Study of bacteria is called bacteriology. Linnaeus placed them under genus vermes. Nageli classified bacteria under schizomycetes. Bacteria are unicellular, microscopic and cosmopoliton organisms. The branch of science, which deals with the study of microorganism and their process is called as microbiology. Antony Von Leeuwenhoek is known as father of microbiology and father of modern microbiology is Robert Koch. These are the smallest cell wall having prokaryotic cell. The bacteria constitute a highly specialised group of one celled plants. They differ from animals in having a rigid cell wall and being capable to synthesize vitamins. Bacteria were first seen by a Dutch lens maker, Antony Von Leeuwenhoek (1683) who named them animalcules. Louis Pasteur (1822-95) made a detailed study of bacteria and proposed germ theory of disease. Ehrenberg (1829) was the first to use the term bacterium. Robert Koch (1881) found that some diseases like tuberculosis, cholera in man, and anthrax in cattle is caused by bacteria. Lister introduced antiseptic surgery. He used carbolic acid for sterilization of surgical instrument. Pasturization theory was proposed by Louis Pasteur. (1) Size : They are 3 to 5 microns (1m = 1/1000 millimetre or about 1/25,000 inch) in length. A few species of bacteria are approximately 15m in diameter. (2) Shape : The bacteria possess the following forms : Cocci (Gk. Kokkos = Berry) : They are oval or spherical in shape. They are called micrococcus when occur singly as in Micrococcus, diplococcus when found in pairs as in Diplococcus pneumoniae, tetracoccus in fours, streptococcus when found more...

#### Archaebacteria

They are present in rumen (first part of stomach) of cattles. This is simplest and most primitive group of bacteria. The cell wall of these bacteria is made of polysaccharides and proteins (peptidoglycans and muramic acid are absent in cell wall). Further branched chain lipids are present in plasma membrane of archaebacteria, due to which these can face extremes of conditions of temperature and pH. Archaebacteria are considered to be 'oldest of living fossils'. Three main groups of archaebacteria are following. (1) Methanogens : These are strict anaerobic bacteria and mainly occur in muddy areas and also in stomach of cattle, where cellulose is fermented by microbes. These are responsible for methane gas $(C{{H}_{4}})$ formation in bio-gas plants, because they have capacity to produce CH4 from CO2 or formic acid (HCOOH). e.g., Methanobacterium, Methanobacillus, Methanosarcina and Methanococcus. (2) Salt lovers archaebacteria or Halophiles : These are also anaerobic bacteria, which occur in extreme saline or salty conditions (upto 35% of salt or NaCl in culture medium). A purple pigmented membrane containing bacteriorhodopsin is developed in sun-light in these bacteria, which utilizes light energy for metabolic activities (different from photosynthesis). e.g., Holobacterium and Halococcus. (3) Thermoacidophiles : These are the bacteria which are found in hot sulphur springs (upto 80oC). As against first two groups of archaebacteria, these are aerobic bacteria. These have the capacity to oxidize sulphur to ${{H}_{2}}S{{O}_{4}}$ at high temperature and high acidity (i.e., pH 2.0), hence given the name Thermoacidophiles, i.e., temperature and acid loving. $2S+2{{H}_{2}}O+3{{O}_{2}}\to 2{{H}_{2}}S{{O}_{4}}$+ energy. e.g., Sulfobolus, Thermoplasma, Thermoproteus.

#### Actinomycetes

It is a group of unicellular branched filamentous bacteria which resemble fungal mycelia. They grow in the form of radiating colonies in cultures and therefore, commonly called ray fungi. They are Gram +ve chemo-organotrophic, saprotrophic bacteria. Most species are facultative anaerobic. These are generally present as decomposers in soil. The filaments are aseptate (non-septate) branched and very thin (about 0.2 to 1.2 mm in width). The wall contains mycolic acid. They reproduce asexually by means of conidia, which are produced at tips of filaments. The endospores are not formed. Most of these secrete chemical substances having antimicrobial activities called antibiotics. Some of the most common and effective antibiotics are obtained from the different species of the genus streptomyces. Some species are pathogenic and cause diseases in plant, animal and human beings, e.g., Mycobacterium. Some common diseases in plants are yellow ear rot of wheat (Tundu disease) caused by Corynebacterium tritici and scab of potato by Streptomyces scabies.
(1) Human disease
Tuberculosis Mycobacterium tuberculosis hominis
Leprosy Mycobacterium leprae
Buruli's ulcer Mycobacterium ulcerans
Actinomycosis Actinomyces israelii
Diphtheria Corynebacterium diptheriae
(2) Animal disease
Tuberculosis of cattle Mycobacterium bovis
more...

#### Specified Branches of Biology

Acarology : Study of mites and ticks. Actinobiology : Study of radiation effects on organisms. Aerobiology : Study of flying organisms. Agriology : Study of customs of primitive man. Algology : Study of algae. Anaesthesiology : Science for causing insensibility. Angiology : Study of blood vascular system including veins and arteries. Aphidology : Study of aphids (plant lice). Araneology : Study of spiders. Arthrology : Study of joints. Bryology : Study of mosses and liverworts. Carcinology : Study of crustaceans. Carcinology : Study of malignant tissue, tumor and cancer. Cardiology : Study of heart. Chondriology : Study of cartilage. Chorology : Study of the geographical distribution of organisms. Cnidology : Study of coelenterates. Conchology : Study of shells. Craniology : Study of skulls. Cryobiology : Study of effects on life at low temperature. Ctetology : Study of acquired characters of organisms. Dermatology : Study of body covering the skin. Ecobiology : Study of problems of existence of life in the outer space. Epidemiology : Study of infection of parasites or epidemic diseases. Ethnology : Study of mankind. Ethology : Study of behaviour of animals. Etiology : Study of cause of disease. Eugenics : Study of improvement of human race through laws of heredity Euphenics : Study of improvement of human race by altering the proteins during mRNA synthesis i.e. protein synthesis process in cells. This is also called medical engineering. Euthenics : Science of improvement of modern generation of man through better nutrition. Exobiology : Study of possible life outside the earth. Genecology : Study of genetical make up of species or populations in relation to their habitats. Geology : Study of earth and life as recorded in rocks. Gerontology : Study of growing old. Gynaecology : Study of female reproductive organs. Haematology : Study of blood. Helminthology : Study of parasitic worms. Hepatology : Study of liver. Herpetology : Study of reptiles. Hypnology : Study of sleep. Ichnology : Study of fossil foot prints. Kalology : Study of human beauty. Karyology : Study of nucleus, particularly chromosomes. Lepidoteriology : Study of moths and butter flies. Leprology : Study of leprosy. Limnology : Study of fresh water ecology and study of snails. Malacology : Study of molluscs. Malariology : Study of malaria. Mammalogy : Study of mammals. Mastology : Study of breast including teats. Melanology : Study of pigments. Molecular biology : Study of life sciences on molecular level (e.g, nucleic acids i.e., RNA & DNA and proteins). Mycology : Study of fungi. Myology : Study of muscles. Myrmecology : Study of ants and anteaters. Nematology : Study of nematodes. Nephology : Study of clouds. Neonatology : Study of newborns upto the age of two months. Neontology : Science dealing with the life of recent organisms, just reverse to palaeontology. Nephrology : Study of kidney. Neurology : Study of nervous system including brain. Nidology : Study of nests of birds. Nosology : Study of classification of diseases. Obstetrics : Science of midwifery. Odonatology : Study of dragon flies and damsel more...

#### Some Branches of Biology

Anatomy : Study of internal structures of plants and animals after dissection.  Biochemistry : Study of chemistry of living matter (i.e., chemical composition, nature, mode of formation, functioning) in relation to life activities. Cytology :  Study of the structure and functions of cells and their organelles. Ecology : Study of relationship between organisms and environment. Embryology :  Study of developmental stages of organisms upto hatching or birth. Endocrinology : Study of endocrine glands and hormones action in animals. Evolution : Study of the origin of life and the gradual differentiation or descent of species. Histology : Study of tissues by microscopy. Immunology : Study of resistance of organisms to infection. Limnobiology : Study of fresh water lakes, ponds and streams. Morphology : Study of form and structure of animals. Palaeontology : Study of fossils and their distribution in time. Palaeozoology : Study of fossil animals. Physiology : Study of functions of various parts within the organisms. Psychology : Study of related areas of psychology and biology. Radiobiology : Study of effects of radioactivity on life. Taxonomy : Study of classification of organisms and their evolutionary relationships with other organisms. Zoogeography : Study of the distribution of animals over the earth. Zoopathology : Study of diseases of animals.

#### Serendipity and Science

(1) Serendipity is associated with scientific method and it refers to discoveries made unexpectedly or by chance. (2) The term 'serendipity' was coined to Horace Walpole in 1754 from the title of the fairy-tale. 'The Three Princes of Serendip (a former name for Sri Lanka)', whose heroes were always making discoveries by accidents and sagacity. (3) Louis Pasteur said that "chance favours the trained mind". because an inquisitive, enthusiastic and intuitive mind may perceive the desired direction for a discovery. (4) In 1922 while Alexander Fleming, the British bacteriologist has a cold, allowed few drops of his nasal mucus to fall on a bacterial culture. (5) Fleming was excited to find sometime later that the mucus could dissolve away the bacteria and the enzyme lysozyme which dissolves bacterial cells could be discovered. (6) One of the best known antibiotics, penicillin, was discovered by Fleming in 1928 as a result of a happy accident. (7) Fleming had been working on Staphylococcus and it happened that some spores of a mould floated into his laboratory through an open window and landed on one of his Staphylococcus colonies. (8) To Fleming's surprise the bacteria were quickly destroyed. (9) The mould was subsequently identified as Penicillium notatum; for this reason the active substance killing the bacteria was called penicillin. (10) Edward Jenner, an English physician, could develop smallpox vaccine by observing that the dairymaids infected with milder cowpox are safer from infection of smallpox. (11) In 1796, Jenner inoculated an 8-year old boy with fluid from cowpox blisters on the hand of a dairymaid, Sarah Nelms. (12) To Jenner's surprise, the boy had become immune to smallpox and this technique of inducing immunity became known as vaccination (Latin 'vacca' means cow)

#### Scope of Biology

Biology creates an awareness of vast array of forms of life which normally goes unseen. Biology offers a large scope and provides a large field for study. (1) Helps us to understand ourselves better : It unfolds different queries of life alongwith its cultural, social, philosophical and economical aspects. So it helps in understanding the life better. (2) Biology and inter-relationship of living beings : Study of biology helps us in understanding the wonderful phenomenon and laws of nature which finally tell us to predict the behaviour of different living beings under changed conditions. (3) Biology and resources : Biology helps us to know how to tap and conserve the resources available to us e.g. fishes, birds, forests etc. (4) Biology and literature : Knowledge of Natural Biology has greatly enriched the literature with their references in stories and poems etc. Poets and other authors have been inspired by the beautiful and interesting plants and animals and frequently figure them in stories, poems and dramas. (5) Study of nature is a rewarding experience : Many plants like Narcissus, Dahlia, Gloriosa, Roses, Marigold, Aster, etc. are used for ornamental purposes. The variety available in animals is widely enjoyed in zoological parks. Students enjoy excursions to remote places watching never seen before plants and animals. (6) Solving problems : Biology makes us to understand the present day problems such as population growth, pollution, conservation of wildlife and survival of man etc. The future directions of biotechnology, conservation of biodiversity, maintenance of environment  and human welfare remain in the hands of biologists. (7) Biology-Medicinal aspect : Several plants like Atropa belladona, Cinchona are sources of atropine, quinine etc. Many members of fungi such as Penicillium and Streptomyces give rise to antibiotics like penicillin and streptomycin. Plants are the major source of vitamins. Drugs are first tested on animals before being used for treating man. Animals provide scientific hints for the production and use of medicines. Animals are widely used for scientific research and results thus obtained are finally applied to man. The study of animal play an important role in health, nutrition and control of pests. Many diseases like malaria are caused and transmitted by animals. (8) Solving approach of biology : Knowledge for eradication of diseases like malaria, small pox, etc. have been achieved by scientists basically due to desire and determination to solve the problem. (9) Ecosystem and living organisms : Biology helps us in understanding the various ecosystems. The living community and non-living environment interact with each other and exchange of material in them takes place. (10) Biotechnology : Biotechnologists have produced many genetically modified (GM) crops. Plenty of studies are being made by geneticists, evolutionists and cytologists to fudge the efficacy of biotechnology.

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