Science : The term science is derived from Latin word scientia which means knowledge. So, the term ‘science’ is used for knowledge gained by actual observation, found correct on verification and put in a systematic manner or science provides us information based on facts. There are several branches of science, each dealing with a specific subject.

         Biology : It is the combination of two Greek words bios and logos. Bios means life and logos means study. Thus, biology is the branch of science which deals with the study of life. The first major biological observations were made by ancient Greek naturalist Aristotle (384-322 B.C.). Aristotle has been designated as Father of biology. The term biology was given by French naturalist Lamarck (1744-1829). Biology has been further classified into,

       (1) Botany                        (2) Zoology.

       The science of plants is called Botany. The word botany has been derived from Greek word botane which means pasture or plants. Technically, botany is called Phytology (Gk. phyto = plants; logos = study). Theophrastus (370-287 B.C.) is known as Father of botany. Zoology  is the study of animals (Gk. zoon = animals; logos = study).  Aristotle is called Father of zoology. Being broad-based and with multi-disciplinary approach, the term biology has been replaced by Life Sciences or Biological Sciences.

         Microbiology : It is the branch of biology which deals with different aspects of microorganisms. Leeuwenhock (1632-1723) is called Father of microbiology.

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.

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 flies.

         Odontology : Study of teeth and gums.

         Oncology : Study of tumors.

         Oneirology : Study of dreams.

         Ontogeny : Study of life history of organism through development.

         Oology : Study of eggs of birds.

         Ophiology : Study of snakes.

         Ophthalmology : Study of eyes.

         Organocology : Study of development of organs during embryonic period.

         Organology : Study of organs.

         Ornithology : Study of birds.

         Osteology : Study of bones.

         Otolaryngology : Study of ear and larynx.

         Otorhinolaryngology : Study of ear, nose and throat (ENT).

         Paediatrics : Science of medicine dealing with diseases and disorders of children.

         Palaeontology : Study of fossils and their distribution.

         Parasitology : Study of parasites.

         Parazoology : Study of sponges.

         Phenology : Study of periodic phenomena of organisms e.g. bird migration, time of flowering.

         Phrenology : Study of mental faculties of brain including feeling.

         Phycology : Study of algae.

         Phytopathology : Study of plant diseases (their causes and symptoms).

         Proctology : Study of hindgut including rectum and anus.

         Protistology : Study of protists (a groups of protozoans such as Euglena, volvox etc.).

         Protozoology : Study of unicellular organisms such as protozoans.

         Psychiatry : Science of medical treatment of mental diseases.

         Pteridology : Study of ferns.

         Rhinology : Study of nose and olfactory organs.

         Sarcology : Study of muscles.

         Saurology : Study of lizards.

         Serology : Study of serum, Study of antigen-antibody reactions.

         Serpentology : Study of snakes.

         Sitology : Study of regulation of diet.

         Sonology : Study of hearing.

         Space biology : Study of existence of life in the outer space.

         Speciology : Study of species.

         Splanchnology : Study of visceral organs.

         Stomatology : Study of foregut including buccal cavity and stomach.

         Syndesmology : Study of bony joints and ligaments.

         Synecology : Study of environmental group of organisms such as communities.

         Tactology : Study of structural organization of the body of organisms.

         Taxidermatology : Study of skin and stuffing.

         Teleology : Study of interpretations of structures in terms of purpose and utility.

         Teratology : Study of monstrals and foetal malformations.

         Termitology : Study of termites.

         Torpedology : Study of skates and rays.

         Toxicology : Study of toxic effects of drugs and harmful compounds.

         Therapeutics : Science of healing.

         Traumatology : Study of wounds.

         Tricology : Study of hairs.

         Trophology : Study of nutrition.

         Urology : Study of urine and its diseases.

         Venereology : Study of venereal diseases.

         Virology : Study of viruses.

         Zoophytology : Study of drifting organisms such as diatoms.

                      Zootechny : Science of breeding and domesticating animals.

         Zymology : Study of fermentation.

Fathers of Various Sciences

         Father of Zoology and Biology and Founder of Embryology  :  Aristotle

         Father of Botany : Theophrastus

         Father of Genetics : G.J. Mendel

         Father of Evolutionary ideas  : Empedocles

         Father of Eugenics : Francis Galton

         Father of Mutation : Hugo de Vries

         Father of Modern Embryology : Karl Ernst Von Baer

         Father of Palaeontology : Leonardo da vinci

         Father of Taxonomy : Carolus Linnaeus

         Father of Special Creation Theory : Father Saurez

         Father of  Blood groups : K.Landsteiner

         Father of Blood circulation  : William Harvey

         Father of Comparative Anatomy : G. Cuvier

         Father of Modern Genetics  : T. H. Morgan

         Father of Medicine : Hippocrates

         Father of Microbiology : Louis Pasteur

         Father of Immunology : Edward Jenner

Chronology of biological discoveries

460-377 Hippocrates : Used the plants in medicine (Father of

B.C.         medicine).

384-322 Aristotle : Initiated study of biology  (Father of biology).

B.C.

370-285Theophrastus  : Described 480 kinds of plants in ‘Historia

B.C.         Plantarum’ (Father of botany) and writer of ’cause of plants’.

1590      Invention of the first microscope by Jenssen  and Zacharis Jenssen

1665      Discovery of the cellular structure (cells) in cork : Robert Hooke described in book ‘Micrographia’.

1675      Anatomia Plantarum : Book by Marcello Malpighi.

1683      Initial separation of bacteria : Antony Von Leeuwenhoek (of Holland) ‘animalcules’ named.

1694      Malpighi illustrated stomata and parenchyma.

1694      Camerarius described sexual reproduction of plants and importance of pollination.

1727      Stephan Hales discovered idea of manufacture of food by green plants in sunlight. Father of plant physiology.

1753      Species Plantarum and Genera Plantarum books (Linnaeus) Carl Van Linnae. Systema Naturae, Binomial nomenclature, father of taxonomy.

1759      C.F. Wolff established embryology, gave ‘epigenesis’ concept.

1761      Discovery of the sexuality of plants : Joseph Gottleib Koelreuter.

1779      Discovery of photosynthesis : Jan Ingenhousz.

1783      First studies of the biology of flowers : Christian Konard Sprengel.

1790      Metamorphosender pflanzen concept of plant metamorphosis : Johann Wolfgang Von Goethe.

1802      Lamarck and Treviranus proposed the term ‘Biology’.

1804      Researches chimiques surla vegetation, discovery of the gaseous exchange of plants : Nicolas Theodore de Saussure.

1809      J.B. Lamarck. Theory of inheritance of acquired characters ‘philosophie zoolozique’ book, use and disuse concept.

1809      Charles Darwin (England) voyage on ‘Beagle’ ship, ‘origin of species’ (1859) book. Theory of natural selection and survival of fittest influenced by Malthus.

1817      P. Caventon, discovery and naming of chlorophyll.

1824      Discovery of endosmosis by H.J. Dutrochet, also suggested that all plants and animals are made of cells.

1828      Brownian movement : Robert Brown.

1830      J.E. Purkinje studied movements and pollination.

1831      ‘Nucleus’ in plant cells : Robert Brown

1835      Nucleolus named by Bowman (1840) and first seen by Fontana (1781) but described by Schleiden M.J. (1835)

1835      Named Sarcode for cell fluid : Dujardin M. J.

1837      Named protoplasm : Purkinje J. E.

1838      T.R. Malthus : Suggested that human population increases much faster than food production.

1839      G.J. Mulder : Named proteins.

1839      Cell theory by German Scientists M.J. Schleiden  (Botanist) and T. Schwann (Zoologist).

1840      Study of cell division : Hofmeister.

1840      Mineral nutrition of plants, established overthrow of the humus theory : Justus Von Liebig.

1842      R. Mayer : Light energy changed to chemical energy in photosynthesis.

1844      Properties of protoplasm : Hugo Von Mohl.

1845      Law of conservation of energy : Julius Robert Von Mayer.

1846      Plant cells arise from pre-existing cells : K. Nageli.

1851      Discovery of the homologies in plant reproduction : Wilheim Hofmeister.

1854      Thuret observed sexual union in algae Fucus.

1857      George Bentham and Joseph Dalton Hooker published ‘Genera Plantarum”.

1858 , ‘Omnis cellula e cellula’ (cells originate from pre-existing cells) R. Virchow.

1859      C. R. Darwin : Theory of Natural Selection, ‘Origin of species‘  book.

1861      ‘Protoplasmic Theory’ : Max Schultze.

1862      A. Kolliker introduced the term ‘cytoplasm‘

1863      Proposition of natural system of classification of angiosperms. George Bentham together with Sir Joseph Dalton Hooker.

1864      L. Pasteur : Proposed germ theory of diseases.

1865      ‘Plastid’ name given : E. Haeckel.

1866      Haeckel ‘Recapitulation theory, coined the term protista.

1866      G.J. Mendel Austrian monk : Laws of inheritance (Heredity). Father of genetics, worked on pea plant.

1868      T. H. Huxley : Protoplasm as the physical basis of life.

1869      Isolation of nuclein (DNA) from nuclei of pus cells : F. Meischer.

1870      W. His invented microtome.

1873      E. Strasburger observed cell division and nuclear division.

1875      Hertwig and Van Beneden both described fertilization between sperm and egg nuclei.

1876      Identification of the Anthrax bacillus as a pathogen of cattles : Robert Koch..

1878      J. Lister : obtained pure cultures of bacteria for the first time.

1878      W. Kuhne coined the term  ‘enzymes’ for ‘ferment’ of yeast.

1880      Discovery of mitochondria : A. Kollicker.

1882      ‘Chromatin’ : W. Flemming, described chromosome splitting used the word ‘mitosis’.

1883      Schimper named chloroplasts, the special bodies of Sach (1865) and green granules of Comparatti (1791).

1884      E. Strasburger : Observed fertilization and cell division in plants, used terms cytoplasm and nucleoplasm.

1886      John Ray published ‘Historia Generalis Plantarum’.

1888      ‘Chromosome’ name W. Weldeyer but first seen by Hofmeister (1848)

1888      Centrosome and centriole : T. Boveri.

1892      D. Iwanowski (Russian) discovered T.M.V. virus.

1892      A. Weissman (1834–1914) : Theory of germplasm.

1892      D. Hertwig : Published monograph ‘The cells and tissues’ established ‘cytology’.

1893      Astral–rays : Fol.

1894      R. Altmann : Discovered mitochondria described as bioplast.

1895      Dixon and Jolly advocated cohesion tension theory for ascent of sap.

1897      ‘Mitochondrion’  : C. Benda.

1898      E. Buchner named ‘Zymase’ the enzymes of yeast.

1898      S. G. Nawaschin recorded double fertilization in angiosperms.

1898      Camilio Golgi discovered golgi apparatus in nerve cell of owl.

1899      Altmann : Introduced term ‘nucleic acids’ to replace nuclein.

1899      Adolf Engler and K. Prantl published ‘Die Naturlichem Pfianzenfamilen system’ of plant classification.

1900      Rediscovery of Mendel’s laws : Erich Tschermak; Carl Correns and Hugo de Vries.

1901      Die Mutations theory : Studies on Oenothera, theory of mutations– Hugo de Vries (1840–1935).

1901      Jule and Merbeck : Parthenogenesis.

1902      C. E. McClung : Identified sex chromosomes in grasshopper.

1902      ‘Chromosome theory’ : Sutton and Boveri.

1904      Blakeslee : Discovered ‘heterothallism‘ in Mucor.

1905      W. Bateson : Coined the term ‘genetics’.

1905      Robert Koch :’Microbiology’ term given; gave Koch’s postulates for germ theory.

1905      Name ‘meiosis‘ : Farmer and Moore.

1908      Winkler : Apomixis.

1909      W. L. Johansen coined the word ‘gene‘

1915      R. M. Willstater : Structure of chlorophyll.

1915      Twort and d’ Herelle : Bacteriophage.

1920      Garner and Allard : work on Photoperiodism.

1921      C.C. Bridges : Discovered duplication, deficiencies and translocations in chromosomes.

1924      Feulgen and H. Rossenbeck : Staining of DNA in cells.

1924      Oparin : Origin of life, materialistic theory.

1926      T. Svedberg : Invented ultra–centrifuge (Nobel Prize).

1926      Went : Carried out avena curvature test (auxins).

1928      Griffith : Transformation in pneumococcus bacteria.

1929      A. Fleming : Discovered Pencillin antibiotic from Penicillium notatum.

1930      Fuelgen and Behrens : RNA in cells.

1931      Zirnike : Phase contrast microscope.

1931      O.H. Warburg : Respiratory pigments and enzymes (Nobel Prize).

1931      Van Niel : Photosynthesis in sulphur bacteria, photolysis (origin from water).

1932      Electron microscope : M. Knoll and E. Ruska.

1933      T.H. Morgan was awarded Nobel Prize for development of gene theory, discovered linkage of genes.

1934      Kogl and Haagen Smit isolated IAA from human urine.

1934      John Hutchinson put forward phylogenetic system of plant classification.

1935      James Danielli and H. Davson proposed a molecular model of plasma membrane, showing trilamellar structure.

1935      Tensley : Ecosystem term given.

1935      Crystallization of the tabacco mosaic virus (TMV) :  W.M. Stanley.

1937      Robin Hill : Demonstrated the release of molecular oxygen by illumination of isolated chloroplasts in photosynthesis.

1937      Hans Krebs explained citric acid cycle.

1938      Yabuta and Sumiki : Isolated the first Gibberellin from Gibberella fujikuroi.

1941      Ruben and Kamen : Used  isotopes to prove photolysis of water in photosynthesis.

1944      Beadle and Tatum : One gene one enzyme concept (Neurospora).

1944      Claude : Microsomes.

1944      Avery, Mcleod, McCarthy proved DNA genetic material.

1945      S. Waksman : Streptomycin, used term antibiotic (Nobel Prize).

1945      Porter and Thompson : Endoplasmic reticulum.

1946      J. B. Sumner : Crystalized first enzyme urease.

1946      J. H. Northorp and W. M. Stanley : Enzymes and virus proteins purified.

1946      H.J. Muller : X–ray induced mutations (Nobel Prize).

1946      Lederberg and Tatum : First indication of sexuality in bacteria.

1951      M.H.F. Wilkins : X-ray diffraction studies of DNA.

1952      Hershey and Chase : DNA as infective part of bacteriophage.

1953      H. A. Kreb’s : ‘Citric acid cycle’ (Nobel Prize).

1953      J. D. Waston,, F.H.C. Crick and Wilkins gave DNA model and shared Nobel Prize 1962.

1953      F. A. Lipman : Coenzyme–A.

1953      Transduction in bacteria : Zinder and Lederberg.

1954      Arnon D. : Photophosphorylation in chloroplast.

1955      Ribosome : G. E. Palade.

1955      Christian de Duve discovered lysosomes and coined the term.

1955      Hoagland : Transfer RNA.

1956      S. Ochoa succeeded in invitro synthesis of polyribonucleotides (RNA) Nobel Prize.

1957      Fraenkel Conrat  : RNA as genetic material in TMV (virus)

1958      Lederberg : Genetic recombination in bacteria, (Nobel Prize).

1959      Arthur Kornberg was awarded Nobel Prize for in vitro synthesis of DNA.

1959      Unit membrane : Robertson.

1959      Butle et al : Phytochrome.

1960      M. Calvin : Carbon fixation cycle (Nobel Prize).

1960      Jacob and Monod : Messenger RNA.

1961      Beevers : Glyoxysomes in plant cells.

1962      Menke : Thylakoid in chloroplasts.

1962      Kendrew and Perutz  : Structure of proteins.

1963      Nass and Nass : DNA in mitochondria.

1963      Saffarman and Morris : Cyanophage virus with DNA.

1964      Osgoods et al : Multistranded chromosomes.

1964      Leninger : Oxysomes in mitochondria.

1964      Yanofsky : ‘One cistron one polypeptide theory’.

1964      Park and Biggins isolated quantosomes in the unit membrane of granum disc of chloroplast.

1965      Bernfield and Nirenberg : ‘Degeneracy’ in genetic code.

1965      F. Jacob and J. Monod  : ‘Operon’ model (operator, regulator genes) Nobel Prize.

1965      Jacob and Wollman : Episome.

1967      M.D. Hatch and C.R. Slack: Dicarboxylic acid cycle (cycle).

1968      Tolbert et al : Peroxisomes.

1968      M.W. Nirenberg, H.G. Khorana and R.W. Holley were awarded Nobel Prize jointly for their discovery which led to breaking of genetic code.

1969      M. Delbruck, A.D. Hershey, S.E. Luria : Virus reproduction (Nobel Prize).

1969      Khorana synthesized ‘gene’ artificially in test tube, DNA ligase enzyme.

1970      Borlaug : Rust resistant high yield wheat varieties and peace (Nobel Prize).

1970      Crick and Klug : Nucleosome model of DNA.

1970      Dannielli : Test tube synthesis of cell.

1971      E.W. Sutherland : Role of cyclic AMP (Nobel Prize).

1972      R.R. Porter and G. M. Edelman : Chemical nature of antibodies. (Nobel Prize)

1974      A. Claude : Virus in cancer tumour cells, cell centrifugation technique (Nobel Prize).

1974      G.E. Palade : Nobel Prize for ribosome discovery.

1974      C. Duve : Nobel Prize for lysosome discovery.

1975      R. Dulbecco, H.M. Temin, D. Baltimore : Nobel Prize for RNA virus in cancer, and reverse transcriptase for coding DNA from RNA.

1976      Gajduseck and Blumenberg : Nobel Prize for cancer research.

1978      Arber, Smith and Nathans : Nobel Prize for DNA restriction enzymes.

1978      P. Steptoe and R. Edward : Work on 1st test tube baby.

1981      Sperry, Hubel and Weisel : Nobel Prize in medicine.

1982      S. Bergstroem, B. Samueleson and J. Vane : Nobel Prize for Prostoglandins role.

1983      B. McClintock : Nobel Prize for mobile genetic elements (transposons = jumping genes) in maize.

1984      K. J. Niels, G. E. Kochlar and C. Milstein : Nobel Prize for monoclonal antibodies.

Biology in Ancient India

       References of classification of organisms are available in Upanishads and Vedas (1500 B.C. to 600 B.C.). However, earliest human activity can be traced back to early, middle and late stone age (400,000 B.C. – 200,000 B.C.).

         About 740 plants and 250 animals have been mentioned in Vedic literature. Few significant references in old literature are,

         (1) Chandyogya Upanishad : Here the animals have been classified into three categories –

         (i) Jiraja (Viviparous) e.g. mammals.

         (ii) Andaja (Oviparous) e.g. birds, reptiles, insects and   worms.

         (iii) Ubhija (Vegetal origin) e.g. small animals.

         (2) Susruta Samhita (600 B.C.) : Here organisms were classified into,

         (i) Sthavara in which immobile organisms like plants were kept.

         (ii) Jangama in which mobile organisms like animals were placed.

Medical Science in Ancient India

       Two Ashwini Kumars has been said to be practising medicine during Vedic times. Dhanwantri has been called as ‘God of medicine’. Susruta has been called as ‘Father of surgery’. Few important references are,

         (1) Susruta studied human anatomy on dead bodies.

         (2) Susruta carried plastic surgery on human nose (rhinoplasty).

         (3) Ophthalmic surgery : Susruta carried an eye surgery like extraction of cataracts.

         (4) Clotting of blood : Susruta used non-poisonous live leeches for checking clotting of blood in post operative conditions. Now its clearly established that heparin is released along saliva of leeches to produces this kind of effect.

         (5) Charaka Samhita (100 B.C.) : It is said to be primarily written by Agnivasa under the guidance of Atreya (600 B.C.). Charaka was first to discuss the concepts of digestion, Metabolism and immunity.

         (6) Taittiriya Upanishad (7–8 B.C.) : In this significant observations have been made about the process of evolution. According to this life originated in space.

         (7) Manu Samhita or Manu Smriti (200 A.D.) : In this significant Sanskrit literature, evolution has been widely discussed.

Table : 1-1 Differences between Plants and Animals

Characters	Plants	Animals
Photosynthesis	Show photosynthesis.	Do not show photosynthesis.
Chlorophyll	Contain chlorophyll.	Lack chlorophyll.
Dependence	Dependent upon inorganic substances like  and .	Feed on complex organic compounds.
Movement	Are fixed organisms but show bending, twisting etc.	They are capable of moving the whole body.
Branching	Have branched body.	Have compact body.
Sensitivity	Are comparatively less  sensitive and respond slowly.	Are more sensitive and respond quickly.
Cell wall	Cellulose cell wall usually present.	Bear no cellulose cell walls.

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)

Biology is a Science of Exceptions

       Exceptions are inherent in biology due to evolutionary divergence. Not only living organisms, but viruses and biomolecules also exhibit exceptional forms. A student of biology must be prepared to accept and enjoy this gesture of nature.

         Some exceptions have been explained logically, while for others, the reasons are yet to be searched out. Following are noteworthy exceptions in zoology,

         (1) Mammals are usually terrestrial, fossorial or arboreal but bat is only flying and whale and seals are aquatic mammals.

         (2) Mature mammalian RBCs are devoid of nucleus except camel.

         (3) The aquatic larval stage of some salamanders like Ambystoma is able to reproduce (paedogenesis) and attain sexual maturity. It is called neoteny. Total neoteny is found in Necturus, Siren and Proteus.

         (4) Heart is three chambered in reptiles but four chambered in crocodiles. It is two chambered in fishes but three chambered in lung fishes like Protopterus which possess lung-like structure beside gills.

         (5) DNA is double stranded in all cells and DNA viruses but single stranded in the bacteriophage  and M-13. Likewise RNA is single stranded in all the cells and RNA viruses but double stranded in reovirus, rice dwarf virus and wound tumour virus.

Science and Technology

       Scientific investigations may be basic or applied. Inventions of new technology extend new hopes and open avenues for the work and research which was not possible earlier. Discovery of radioactive isotopes enabled tracing metabolic pathways, development of microscope and then electron microscope provided useful tools to study biology. X-ray crystallography helped in the study of the structure of DNA, protein and many other biomolecules. Biotechnology and genetic engineering are fruitful due to accumulation of knowledge from different sources. It is note worthy that while information gathered from basic researches enriched the field of applied researches, the fruits of applied researches contribute to explore and widen the area of basic researches.

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.

Methodology of Science

       A scientist link patterns or draws relationship among a number of isolated facts. Scientist is responsible for determining the principles from the observations on specific cases and finally discovers general principles. Scientists adopt scientific methods based on the following pattern –

Careers in Biology

         Some interrelated disciplines of biology (career options in biology) from which any field can be selected for further rewarding career.

         (1) Virology : It is the study of viruses.

         (2) Agronomy : This branch deals with the management of farms and is the science of crop production.

         (3) Pathology : It is the study of diseases (their nature, causes, symptoms, effects and control).

         (4) Breeding : This branch is concerned with the production of new improved races by mating selected parents.

         (5) Entomology : It is the study of structure, habits and classification of insects.

         (6) Anthropology : It is the study of physical, cultural, mental and social nature of primitive and modern man.

         (7) Veterinary science : It deals with the study of domestic animals.

         (8) Ichthyology or Fishery or Pisciculture : It deals with the study of rearing fish.

         (9) Apiculture : It deals with the study of bee-keeping for obtaining honey and wax.

         (10) Poultry : It is the branch of science dealing with the study of raising domestic fowls as chicken, ducks and geese.

         (11) Food technology : It is the study of processing and preservation of foods, vegetables, fruits, etc.

         (12) Nutrition : It supplies information for proper nourishment of human and other organisms for healthy living.

         (13) Forestry : It is concerned with protection and development of forests and to explore the outcome and economic potential of forests.

         (14) Horticulture : It is the study primarily aimed at the improvement of ornamental and fruit yielding plants.

         (15) Pharmacology : It deals with study of drugs and preparation of medicines.

         (16) Bacteriology : It aims at the study of bacteria and includes the exploration of useful and harmful effects.

         (17) Genetics : The branch which is concerned with differences and resemblances among parents and progeny especially those due to heredity or inheritance.

         (18) Pharmacy : It deals with the preparation and compounding medicines and dispensing them as per doctor’s prescription.

         (19) Soil Science : It aims at the study of soil, its structure, type and dynamics.

         (20) Dairy technology : It is the study of manufacture of milk products.

         (21) Microbiology : It is the study of microscopic organisms.

         (22) Psychology : The branch of science which deals with behaviour and qualities etc. of human mind.

         (23) Forensic Sciences: It is the application of scientific knowledge to the question of civil and criminal laws e.g., study of finger prints, blood typing, identification of narcotics etc.

         (24) Medicine: The branch of science responsible for curing diseases with drugs or other curative substances.

         (25) Surgery: It is a branch of medicine which deals with physical operations to cure injuries and other diseases of body.

         (26) Biomedical engineering: It deals with the production of spare parts of man such as artificial limbs, implants and heart, lung machine etc.

         (27) Physiotherapy : It is the branch of science which mainly aims at curing the diseases, defects and body weaknesses by physical remedies as massage and exercise etc.

         (28) Genetic engineering : It is a branch of genetics which deals with production of organism with combination of new heritable characters at will (gene-manipulation).

         (29) Occupational therapy : It involves the cure of convalescents and physically handicapped by doing light work for diversion, physical exercise or vocational training.

         (30) DNA finger printing : By this technique a person can be identified on the basis of his genes as no two persons can have identical sub-genetic make up.

         (31) Bioinformatics : This branch of biology deals with the systematic development and application of computing systems and computational solution of techniques, analysing data obtained by experiments, modelling, database searching and instrumentation to make novel observations about biological processes.

         (32) Computer simulation : It is the conversion of physiological phenomena into graphical and multidimensional and multimedia presentation without actually involving plants/animals.

         (33) Computational biology : It deals with systematic development, application and validation of computational hardware and software solutions for building simulation models of biological systems.

         (34) Prawn Farming : It deals “with” rearing, transportation and marketing of prawns.

         (35) Medical transcription : It deals with interpretation and typewriting (transcribing) dictation from physicians and other health care providers regarding patient assessment and work-up surgical, radiology and therapeutic methods, clinical course, diagnosis and prognosis etc.

Misuse of Biology

(1) Amniocentesis : However, these days, the amniocentesis is being misused also. Mothers even get their normal foetus aborted if it is a female. This is just equivalent to killing of a normal child. So Govt. of India enforced the Pre-natal Diagnostic Techniques (Regulation and Prevention of Misuse) Act, 1994 since January 1, 1994 under which all genetic counselling centres and laboratories are required to apply for registration. So this technique has been banned in some states like Maharashtra and is under consideration in other states.

(2) Bioterrorism : Now a days bio-techniques are being widely used for preparation of bioweapons like antibiotic resistant  micro-organisms. Spores of Bacillus anthracis (cause of anthrax) are produced in biology research labs and stored for decades. Their release may cause anthrax and become the cause of bioterrorism. Such release of antibiotic resistant strains cause communicable diseases like anthrax and plague on endemic or epidemic scale.

 

 

Basic Properties of Living Organisms

       Living beings are called organisms. Living organisms are similar to non-living objects in being – formed of similar elements which combine in similar way to form similar molecules (called biomolecules in living organisms) and follow similar physical and chemical laws like gravitation, magnetism, action and reaction etc. living organisms show a great biodiversity and are classified into different kingdoms-Monera, Protista, Fungi, Plantae and Animalia. But all of these share the following properties –

         (1) They have definite organisation.           

         (2) They always have cellular nature so are either unicellular (e.g. Amoeba, Paramecium etc.) or multicellular (e.g., Hydra, man etc.).

         (3) They show co-ordination between different parts of body to maintain homeostasis (constant internal environment) inside the body.

         (4) They have the ability of movements and locomotion.

         (5) They show metabolic functions in the presence of energy.

         (6) These have the ability of intussusceptional  (internal) growth and development.

         (7) These have specific receptors (e.g., sense organs to receive external and internal stimuli) and specific effectors (e.g., muscles and glands to give specific response).

         (8) These have regulatory mechanisms (e.g., nerves and hormonal in animals, and only hormonal in plants) to maintain homeostasis inside the body.

         (9) These show adaptations to their environment to increase their chances of survival.

         (10) These show variations which help in speciation and evolution.

         (11) These have reproductive powers for continuity of their race.

         (12) These have definite life span (period from birth to death).

         (13) These undergo ageing after adulthood and then natural death.

Levels of Biological Organization

            (1) Levels of Organization common in both living and non-living

       (i) Atomic level : The lowest level of organization in both living and non-living is the atom. All living organisms are basically made up of four chemical elements carbon (C), hydrogen (H), oxygen (O) and nitrogen (N) with only about 1% other elements. The non-living matter may possess other elements (such as silica, calcium, iron, etc.) in variable composition.

         (ii) Molecular level : Atoms combine to form molecules, which undergo chemical reactions to form organelles.

       Atoms ® Molecules ® Inorganic compounds ®  Simple organic  compounds ® Complex organic compound ® Protoplasm ®  Cell.

         (2) Levels of Organization found only in living organisms

         (i) Cellular level : All multicellular organisms are made up of cells. The cell is considered as basic unit of life and constitutes the smallest level of organisation of the living organisms.

         (ii) Tissue level : In multicellular organisms similar or dissimilar cells, having a common origin and a common function, combine to form a tissue. Each tissue performs a specific role (e.g., xylem conducts water and minerals in plants).

         (iii) Organ level : Different tissue are organised to form distinct organs. For example, xylem, phloem chlorenchyma, parenchyma get organised to form a leaf.

         (iv) Organs System level : A group of organs that coordinates to performs a major function forms the organs system. For example, the brain works with the spinal cord and a network of nerves to form the nervous system.

         (v) Individual or Organismic level : A multicellular individual, having many organ systems, forms an organismic level of organisation.

         Cell ® Tissue ® Organ ® Organ system ® Individual.

         (3) Levels of organization beyond the individual organism

         (i) Population level : All the individuals of a species in a particular area, where they interact with each other, belong to a population. For example, there is a population of Oak trees in a temperate deciduous forest.

         (ii) Community level : The populations of different species of plants and animals present in a particular area make up biotic community.

         (iii) Ecosystem level : Populations of different plants and animals interact among themselves and with the non-living components of the area form as ecosystem.

         (iv) Biosphere level : The different ecosystems (small or big) of all the geographical regions of the world form the biosphere or the entire livable part of the earth.

Types and significance of chemical bonds

       A chemical bond is an attractive force that links two atoms to form a molecule. Chemical bonds act like a powerful ‘glue’ that holds atoms close together. Three kinds of chemical bonds are: ionic bonds, covalent bonds and hydrogen bonds.

         (1) Ionic Bonds

         (i) When an atom loses or gains a valence electron, ions are formed.

         (ii) Positively and negatively charged ions are attracted to    one another.

       (iii) When this force of attraction holds ions having opposite charges together, it is called ionic bond.

       (2) Covalent Bonds

         (i) When a covalent bond forms, neither of the combining atoms loses or gains electrons.

         (ii) Instead, the atoms form a molecule by sharing one, two or three pairs of their valence electrons.

         (iii) The greater the number of electron pairs shared between two atoms, the stronger the covalent bond.

         (iv) Covalent bonds are the most common chemical bonds in living organisms.

         (v) The compounds that result from them form most of the body’s structures.

       (3) Hydrogen Bonds

         (i) A hydrogen bond is a weak bond it has greater  advantage in biological systems.

         (ii) An atom of hydrogen that forms a polar covalent bond with an oxygen atom or nitrogen atom may form hydrogen bond with an electronegative atom.

         (iii) The polar covalent bond causes the hydrogen atom to have a partial positive charge of neighbouring electronegative atoms, often oxygen or nitrogen.

Building blocks of life and their function

       Living organism is formed of many types of inorganic as well as organic biomolecules. Inorganic compounds include water, minerals etc. and are always micro-biomolecules (small sized, low molecular weight, readily soluble in water and diffusible) while organic molecules may be micro (e.g. monosugars, amino acids etc.) or macro-biomolecules (large sized, high molecular weight, insoluble or slightly soluble and non-diffusible e.g., proteins, fats, nucleic acids, etc.). These Both types of biomolecules play important roles in metabolism :

         (1) Role of Water : Water forms 70-90% of the cellular pool. It forms 65% (about two-thirds) of human body. It is formed of H and O in the ratio of 2:1. 95% of water is found in free state and 5% in combined form in the cell. Water helps in sustaining the life processes. So water is called elixir or cradle of lip as life is not possible in the absence of water.

         (2) Role of Oxygen : Oxygen is mainly utilized in aerobic cell respiration of the nutrients inside the mitochondria to produce energy-rich ATP molecules so is essential for life. In the absence of oxygen, only 5% of energy available is released.

         (3) Role of Sodium chloride (common salt– : Sodium chloride plays important roles in metabolic functions of body especially when in ionic form.

         (4) Role of Carbohydrates : Carbohydrates are organic compounds formed of C, H and O generally in the ratio of 1:2:1. These are commonly called saccharides (Gk. saccharon = sugar) Carbohydrates are the main storage molecules and most organisms use carbohydrates as an important fuel, breaking these bonds and releasing energy to sustain life.

         (5) Role of Proteins : Proteins are polymeric compounds formed by interlinking of amino acids (monomers) by peptide bonds. Out of about 100 types of amino acids, only 20 types of amino acids are of biological importance, so are called Magic-20. Proteins play a vital role in the formation of structures in living organisms. Like carbohydrate and fat, protein can be broken down with the release of energy. Protein is not stored as such in the body and it is normally only used as a substantial source of energy in conditions of starvation.

         (6) Role of lipids : Lipids comprise a major group of insoluble hydrocarbons having many functions. These are polymers of alcohols (e.g. glycerol) and fatty acids interlinked by esterbonds.

         Complex lipids such as true fats are important organic molecules that are used to provides energy. Fats in animals also provide protection from heat loss.

         (7) Role of Nucleic Acid : These are polymers of nucleotides interlinked by phosphodiester bonds, so called polynucleotides. Each nucleotide is formed of 3 components : a pentose sugar (e.g. ribose in RNA and deoxyribose in DNA), a phosphate group and an inorganic nitrogen-base (a purine or a pyrimidine).

         DNA acts as genetic material in most organisms and controls the synthesis of structural and functional proteins. RNA also act as genetic material in all plant viruses e.g. TMV and helps in protein synthesis.

Matter and Energy

             Technically speaking, matter and energy are interchange able as expressed by Albert Einstein’s famous equation : energy equals mass times the square of the speed of light (c²).

             For the chemical reactions that occur within living organisms, however, we can treat matter and energy as quite distinct from one another. Matter is the physical material of the universe; energy is the capacity to do work.

             Close and Open system : A system is a portion of the universe that is selected within a definite boundary. The part other than the system is called surrounding.

             As system is said to be closed if it can exchange energy but not matter, and in this energy can be gained or lost (through stainless walls) but not matter. A system said to be open if it can exchange matter and energy with surroundings. All living systems are open systems because they are continuously exchanging matter and energy with their surroundings.

Kinetic and Potential energy

         Kinetic energy is the energy of movement and this include not only movement of large objects but also movements such as electrical energy (movement of electrons) and heat (movement of atoms and molecules).

         Potential energy is stored energy that can be released as kinetic energy under right conditions.

         The food which you eat has chemical potential energy, some of which is converted into kinetic energy.

Laws of Thermodynamics

The laws of thermodynamics describe the basic properties of energy. All interactions among pieces of matter are governed by the two laws of thermodynamics. The laws of thermodynamics deal with “isolated systems” which are any parts of the universe that cannot exchange either matter or energy with any other parts.

First Law of Thermodynamics : The first law of thermodynamics states that energy can neither be created nor destroyed; but energy can change from one form to another.

In other words, within an isolated system the total quantity of energy remains constant. The first law is therefore often called the law of conservation of energy.

Second law of Thermodynamics : The second law of thermodynamics states that the amount of useful energy always decreases when energy is converted from one form to another.

In other words, every transfer or transformation of energy makes the universe disordered; no physical process or chemical reaction is 100 per cent efficient.

Entropy is a measure of the disorder or randomness within a system.

Energy flow

         (1) Energy Transformation : It is the phenomenon in which one form of energy is changed into another form of enrgy. e.g. in photosynthesis (anabolism), radiant (Kinetic) energy of sunlight is changed into chemical (potential) energy of glucose. All the living organisms depend upon this transformation.

         (2) Energy Transfer : It involves the movement of energy from one source or area or substance to another in the same form. e.g. in cell respiration (catabolism), oxidative break down of glucose occurs inside the mitochondria of aerobic plants and animals.

The glucose is enzymatically catabolised by stepped breakdown into water and  and about 686 kcal of energy is released per mole of glucose. A part of released energy is stored as chemical energy in high energy bonds of ATP (adenosine triphosphate) formed by phosphorylation of ADP.

Table : 1-2 Some examples of Energy transformation.

Type of Energy Transformation	Example
Chemical to electrical	Nerve cell
Light to electrical	Retina of eye
Chemical to osmotic	Kidney
Chemical to mechanical	Muscles and cilia
Sound to electrical	Ear
Chemical to light	Bioluminescence
Chemical to heat	Homeothermy

Homeostasis

         Homeostasis (Gk, homoios = same; stasis = standing) is the maintenance of a constant internal environment or steady state (blood plasma, haemolymph, extracellular fluid, etc.). The French physiologist Claude Bernard (1857) realized the importance of stability in the internal environment (milieu interieur). The term ‘homeostasis’ was first coined by the American physiologist Walter Bradford Cannon in 1929. Homeostasis is a fundamental property of life and is considered a good sign of life.

Thermoregulation

         As far as temperature regulation is concerned, animals can be divided into two groups: poikilothermous and homeothermous.

         Poikilothermic means ‘having a variable temperature’. Poikilothermic animals are described as ‘cold-blooded’, their body temperature changing with fluctuation in the environmental temperature. Homeothermic means ‘having the same temperature’. Homeothermic animals (mammals, birds and a few fishes like tuna fish and sword fish) are popularly described as ‘warm-blooded’; their body temperature is independent of environmental temperature.

       In cold conditions their blood is at a temperature higher than that of their surroundings. More useful terms are ectothermic and endothermic. Ectothermic animals, as the word implies, gain heat from the environment, i.e., from outside the body. Endothermic animals generate heat from within the body and keep it there.

Growth

         Growth is one of the most important characteristics of living organisms. Growth is defined as a permanent increase in size or weight or volume of an organism or its body parts e.g. kittens grow into cats, pupies grow into dogs and a human baby grows to become adult.

         At the molecular level, the growth involves,

         (1) Increase in the size of cells due to synthesis of protoplasmic substances like cytoplasm and nucleus.

         (2) Addition of non-living aprotoplasmic materials like intercellular matrix, fibres of connective tissue, etc. These are secreted by the cells.

         (3) Increase in the number of cells by cell division. It occurs through cell cycle which is formed of interphase and M-phase.

         (4) Growth is the result of greater anabolic (synthetic) processes over the catabolic (destructive) processes in an organism.

         The process in which reserve food material is utilized and exhibited negative growth is called degrowth.

Development

         (1) In general, growth involves three processes or strategies namely cell proliferation, cell enlargement and secretion of large amount of extracellular matrix.

         (2) Growth is an important part of development, continuing throughout life.

         (3) Early embryonic developmental stages constitute prefunctional state of life.

         (4) The biological process of growth and differentiation enables the animal to enter the functional state of life.

         (5) Morphogenesis refers to generation of form and structure during development of an individual organism.

         (6) Morphogenesis produces new forms by involving cell movements.

         (7) Morphogenetic movements of large number of cells during development is particularly noticed during gastrulation.

         (8) Differentiation results in increasing diversity of cells.

Reproduction

       (1) Reproduction is one of the most important life functions.

         (2) Reproduction is the only way that living things can perpetuate themselves.

         (3) There are a number of different ways that various kinds of organisms reproduce and compensate for the loss of life due to death.

         (4) some reproductive processes known as sexual reproduction involve two organisms and their sex cells.

         (5) Asexual reproduction occurs when organisms make identical copies of themselves.

Table : 1-3 Differences between Asexual and Sexual Reproduction

Asexual Reproduction	Sexual Reproduction
It involves no formation and fusion of gametes.	It involves formation and fusion of gametes.
It is always uniparental.	it is generally biparental except, Taenia, Fasciola etc.
Reproductive units are somatic cells of parent.	Reproductive units are germ cells of parent.
It involves only mitotic divisions.	It involves meiosis during gamete formation.
Offsprings are generally similar to parents.	Offsprings are genetically different from parent.
Occurs by binary fission or multiple fission or budding or fragmentation.	Occurs by gametogenesis (formation of gametes) followed by fertilization.

Adaptation

       (1) Adaptation may be defined as any characteristic of an organisms which makes the organisms better suited to its environment.

         (2) In other words, an adaptation improves the performance and survival of the organism in its the environment.

         (3) Many adaptations are remarkable; they result from natural selection.

         (4) Individuals with favourable characteristics replace those with less favourable characteristics.

         (5) Adaptation improves the match between organisms and their environment.

         (6) On the basis of their nature and role in evolution the adaptation are classified into short range or temporary and long range or permanent adaptation.

Table : 1-4 Differences between Short-range and Long-range adaptation

Characters	Short-range adaptations	Long-range adaptations
Nature	These are temporary changes.	These are permanent changes.
Development	These are developed in response to temporary changes in the environment.	These are developed in response to permanent change in the environement.
Transmission	These are not inheritable.	These are inheritable.
Genetic material	DNA is not changed.	DNA is also changed.
Role in evolution	No role in evolution.	Important role in evolution.

Life Span

         The average longevity of an organisms from birth to death is called life span. It is different in different living organisms. The life span of some common plants and animals has been listed in Table.

Table : 1-5 Life Span

Organism	Average life span
May-fly	1 day
Silk moth	2-3 days
Wheat	5 months
Rat	4 years
Rabbit	13 years
Monkey	26 years
Dog	20-30 years
Cat	35-40 years
Horse	60 years
Elephant	65 years
Eagle	90 years
Man	60.4 years
Parrot	140 years
Tortoise	200 years
Banyan tree	200 years
White oak tree	500 years
Ficus religiosa (Peepal)	2000-3000 years
Sequoia tree (Red wood tree)	3000-4000 years

Death

         Death is the permanent breakdown and finally stopping of vital functions of body, especially heart beat and respiration.

         Characteristics

         (1) It is the last event in the degenerative processes of ageing.

         (2) Death involves widespread be cell breakdown and cell death.

         (3) Death of an organism involves the death of body cells. But all the body cells do not die at same rate e.g. ciliated cells lining the respiratory tract of mammals continue to beat their cilia for long time even after clinical death.

         (4) There is no natural death in some protists e.g. Amoeba and monerans like bacteria, etc.

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