Chronology of Significant Historical Developments in the Biological Sciences

Biology - 1800 B.C.

• Although Hammurabi's code mentions the practice of hand pollinating date palms, the sexuality of plants was not understood until 1694.

Biology - c. 600 B.C.

• Thales of Miletos believed that all life came from water.

Biology - c. 590 B.C.

• Euclid investigated and recorded some of the properties of curved reflecting surfaces.

Biology - c. 550 B.C.

• Anaximander saw spontaneous generation as a unique historical event, followed by the transmutation of and evolution of different forms. He also theorized the existence of four basic elements, which were earth, air, fire and water.

Biology - c. 520 B.C.

• Alcmæon of Croton dissected animals, distinguished veins from arteries, discovered the optic nerve, and recognized the brain as the seat of thought.

Biology - c. 500 B.C.

• Xenophanes examined fossils and speculated on the evolution of life.

Biology - c. 450 B.C.

• Empedocles of Agrigentum postulated the existence of four humors (blood, phlegm, black bile and yellow bile), derived from the four elements (air, water, earth and fire), of which life was composed.

Biology - c. 440 B.C.

• Hippocrates founded a school of rational medicine in Greece.

Biology - c. 350 B.C.

• Aristotle made detailed observations of marine organisms, proposed an epigenetic theory of development, attempted a comprehensive classification of the animals, and believed that animals could hybridize freely. His written works included Historia Animalium, a general biology of animals, De Partibus Animalium, a comparative anatomy and physiology of animals, De Motu Animalium and De Incessu Animalium, both of which concern primarily animal locomotion, De Anima, on the vital principle, Parva Naturalia, concerning psychology, and De Generatione Animalium, on developmental biology.

Biology - c. 300 B.C.

• Theophrastos produced two great works on plants, Historia Plantarum, and De Causis Plantarum, in which he pursued the classification and physiology of plants.

Biology - c. 300 B.C.

• Herophilos dissected the human body. He is believed to be the first to do so publicly.

Biology - c. 300 B.C.

• Diocles wrote the first known anatomy book and was the first to use the term "anatomy".

Biology - c. 50-60

• Pedanius Dioscorides's De Materia Medica described 600 plants of medical value. Dioscorides also made the first recorded use of anesthesia.

Biology - c. 50-70

• Pliny (Gaius Plinius Secundus) the Elder's Historia Naturalis published in 37 volumes.

Biology - 65

• Lucius Annaeus Seneca reported that glass globules filled with water "will aid in seeing those difficult things which frequently escape the eye."

Biology - 127-151

• Claudius Ptolemy investigated the problem of magnification by means of curved surfaces.

Biology - 130-200

• Claudius Galen performed dissections and wrote numerous treatises on human anatomy. He was considered the authority on anatomy long after his death by those who accepted his word rather than following his investigative methodology.

Biology - c. 1010

• Avicenna (Ibn Sina or Abu Ali al Hussein ibn Abdallah) published his Canon of Medicine (Al-Quanun) which was translated into Latin in 1473 by Gerard of Cremona and remained a useful text well into the 17th century.

Biology - c. 1235

• Roger Bacon established the importance of using experimental methods.

Biology - 1266

• Theodoric Borogoni of Lucca advocated the use of narcotic-soaked sponges to put surgical subjects to sleep.

Biology - 1347

• William of Occam (or Ockham) enunciated the principle now known as Occam's Razor: "What can be explained by the assumption of fewer things is vainly explained by the assumption of more things."

Biology - c. 1450

• Nicholas Cusa (Nikolas von Cusa, Nicolaus Cusanus) suggested that plants grew by assimilation of water.

Biology - 1485

• Leonardo da Vinci stressed the importance of using lenses for the study of small objects. Leonardo was also an accomplished anatomist and invented may ingenious techniques for preparing specimens for anatomical investigation. Unfortunately most of his written work was lost until the eighteenth century.

Biology - c. 1500

• Leonardo da Vinci compared animal nutrition to the burning of a candle, and pointed out that animals could not survive in an atmosphere that would not support combustion.

Biology - 1539

• Hieronymus Bock (Jerome Boch) arranged plants by relation or resemblance. His was the first attempt at a natural classification of plants.

Biology - 1541

• Conrad Gessner (Konrad Gesner) distinguished genus from species and order from class in his classification of plants.

Biology - 1543

• Andreas Vesalius made first modern interpretation of anatomic structures in De Humani Corporis Fabrica. He corrected many of the errors perpetuated by the Galenists.

Biology - 1546

• Hieronymus Fracastorius (Girolamo Fracastoro) wrote On Contagion (De contagione et contagiosis morbis et curatione), the the first known discussion of the phenomenon of contagious infection.

Biology - 1551-71

• Conrad Gessner (Konrad Gesner) published Opera Botanica and Historia Plantarum, works which would influence such later taxonomists as Linnaeus and Cuvier.

Biology - 1553

• Miguel Servet y Reves (Michael Servetus) asserted, in Christianismi Restituto, that blood circulates from the heart to the lungs and back to the left ventricle of the heart.

Biology - 1555

• Pierre Belon's book on birds contained a picture of a bird skeleton and a human skeleton in which the homologous bones in the two species were given the same manes.

Biology - 1559

• Realdo Colombo described the passage of blood from the right side of the heart through the lungs to the left side of the heart.

Biology - 1572

• Volcherus Coeiter (Volcker Koyter) first observed the blastoderm of the chick.

Biology - 1590

• Zacharias Jansen (with the help of his father, Jans) combined two convex lenses within a tube, thus constructing the forerunner of the compound microscope. (Their intention was to construct a telescope.) Jansen was an optician and counterfeiter by trade. He has also been falsely credited with the invention of the telescope.

Biology - 1596

• Caspar Bauhin used a binomial system in the classification of plants.

Biology - 1614

• Sanctorius Sanctorius (Santorio Santorio) published De medicina statica aphorismi. He made quantitative measurements of body weight, total intake, and total excrement; he attributed losses to "insensible perspiration."

Biology - 1616-28

• William Harvey demonstrated his findings on the circulation of blood in lectures and discourses. He correctly deduced the existence of capillaries although he could not see them.

Biology - 1625

• Joseph of Aromatari held that the chick is present in the egg before incubation.

Biology - 1627

• Gaspare Aselli demonstrated the existence of lacteal vessels.

Biology - 1628

• Publication of William Harvey's Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus, in which he described the function of the circulatory system, including the notion of the heart as a mechanical pump.

Biology - 1648

• Publication of Jean Baptiste Van Helmont's Ortus Medicinae, including account of an experiment on plant nutrition from which he concluded that plants derive their substance from water. He coined the word "gas" and described the properties of carbon dioxide.

Biology - 1649

• René Descartes postulated that impulses originating in the sensory receptors of the body were carried to the central nervous system where they activated muscles by what he called "reflection."

Biology - 1651

• Publication of William Harvey's Exercitationes de Generatione Animalium with the aphorism "ex ovo omnia" on the title page.

Biology - 1652

• Thomas Bartholin discovers the lymphatic system and determines its relationship to the circulatory system.

Biology - 1656

• Giovanni Alfonso Borelli investigated the microscopic structure of red blood cells and accurately noted the regularity of stomatal movements. He later demonstrated that locomotion in fish is primarily by the motion of the tail rather than by the fins.

Biology - 1658

• Jan Swammerdam described red corpuscles, lymphatic valves, and alteration in the shape of muscles during contraction.

Biology - 1660

• Nicaise Le Febvre, in Traicte de la chymie, held that the function of air in respiration was to purify the blood.

Biology - 1660-78

• Robert Boyle conducted experiments upon gases and effects of combustion and respiration on the atmosphere.

Biology - 1661

• Marcello Malpighi conducted extensive investigations on the anatomy and embryology of plants and animals. He discovered the existence of capillaries in the lung of a frog--structures predicted to exist by William Harvey some thirty years earlier.

Biology - 1665

• Robert Hooke published Micrographia, a collection of diverse essays dealing with the microscopic structure of familiar substances, among which the cellular structure of cork is fully described and illustrated. He also described microscopic examinations of fossilized plants and animals, comparing their microscopic structure to that of the living organisms they resembled. He argued for an organic origin of fossils, and suggested a plausible mechanism for their formation.

Biology - 1666

• Robert Boyle presented his method of preserving soft-bodied animal specimens in wine spirits.

Biology - 1667

• Nicolaus Steno recognized the homology of the mammalian ovary with that of the egg-laying animals.

Biology - 1668

• Publication of Francesco Redi's Observations on the Generation of Insects. Redi concluded that flies were not produced spontaneously by rotting meat, but rather that they hatch from eggs that are deposited on the meat by other flies. Redi did not deny the phenomenon of spontaneous generation in general, however.

Biology - 1668

• Publication of John Mayow's Treatise on Respiration (Tractus duo), containing accounts of experiments on alterations produced in air by respiration and combustion.

Biology - 1669

• Jan Swammerdam described the metamorphosis of insects, supporting the preformation doctrine.

Biology - 1672

• Regnier de Graaf described ovarian follicles--although he believed they were actually ova--and the passage of the zygote to the uterus.

Biology - 1672

• Nehemiah Grew published an extensively illustrated volume summarizing his detailed studies of plant anatomy.

Biology - 1674

• Nicolas de Malebranche elaborated the conception of emboitement (encasement), which held that each embryo is contained within the embryo of its parent.

Biology - 1674

• Antoni van Leeuwenhoek further improved the art of polishing lenses of short focal length. He discovered and described protozoa, bacteria, rotifers, and the like.

Biology - 1676

• Antoni van Leeuwenhoek discovered "animalcules" or infusoria.

Biology - 1676

• Nehemiah Grew suggested the true nature of ovules and pollen.

Biology - 1677

• Antoni van Leeuwenhoek described human spermatozoa and asserted that they were capable of developing into a child, with the egg providing only nutrient.

Biology - 1678

• Christian Huygens first published a description of spermatozoa.

Biology - 1680

• Publication of Giovanni Alfonso Borelli's De Motu Animalium, in which he applied mechanical principles to the study of animal movement, and discovered that the movement of muscles was due to the contraction the individual fibers.

Biology - 1682

• Publication of John Ray's Methodus Plantarum Novae, in which he distinguished monocots from dicots and first elaborated the biological species concept.

Biology - 1683

• Antoni van Leeuwenhoek discovered bacteria.

Biology - 1686-1704

• John Ray's Historia Plantarum published in three volumes.

Biology - 1689-1698

• Antoni van Leeuwenhoek made detailed observations of capillaries in frogs' feet, bats' wings, rabbits' ears, and the tail of an eel.

Biology - 1693

• Publication of John Ray's Synopsis of Quadrupeds and Snakes, in which he disproved Descartes's claim that animals are insentient, questioned the existence of fabulous creatures, and argued against spontaneous generation.

Biology - 1694

• Rudolph Jakob Camerarius (Camerer) published De Sexu Plantarum Epistola, which presented a conclusive demonstration of the sexuality of plants.

Biology - 1699

• Plantade (Dalenpatius) published fictitious figures of homunculi in sperm cells.

Biology - c. 1700

• Georg Ernst Stahl's phlogiston theory.

Biology - 1705

• Robert Hooke's Discourse on Earthquakes, in which he speculates on the geological mechanisms responsible for the distribution of fossils, is published posthumously.

Biology - 1710

• Publication of John Ray's Historia Insectorum.

Biology - 1713

• Publication of John Ray's Synopsis of Birds.

Biology - 1715

• Thomas Fairchild announced the production of the first artificial hybrid plant.

Biology - 1727

• The famous seed-breeding establishment Vilmorin-Andrieux et Cie was founded. It was through the work of this concern that the sugar beet was developed during the Napoleonic era.

Biology - 1727

• Stephen Hales concluded that plants are nourished in part by the atmosphere. He also studied the ascent of water in plants and applied physical principles to the study of plant physiology.

Biology - 1733

• Stephen Hales made the first measurement of blood pressure.

Biology - 1738

• Jan Swammerdam's description of cleavage in the frog's egg published posthumously.

Biology - 1744

• Pierre Louis Moreau de Maupertuis proposed the theory that molecules from all parts of the body were gathered into the gonads (later called "pangenesis") and speculated on the causes of evolution. He also made pointed criticisms of preformationism while advancing his own refined form of epigeneticism.

Biology - 1745

• Charles Bonnet demonstrated the regenerative ability of annelid worms.

Biology - 1746

• Charles Bonnet discovered natural parthenogenesis in the aphid. He also studied photosynthesis and epinasty in plants.

Biology - 1749-77

• George Louis Leclerc de Buffon regarded spermatozoa as "living organic molecules" which multiply in the semen.

Biology - 1749-1804

• George Louis Leclerc de Buffon's Histoire Naturelle asserted that species were mutable; drew attention to vestigial organs.

Biology - 1752

• René Antoine de Réaumur showed by experiments with a pet kite that gastric juice liquefied meat.

Biology - 1752

• James Lind called attention to the value of fresh fruits in preventing scurvy.

Biology - 1754

• Joseph Black discovered "fixed air" (carbon dioxide).

Biology - 1754

• Charles Bonnet noted the emission of bubbles by a submerged illuminated leaf.

Biology - 1758

• Carolus Linnaeus (Carl von Linné) published Systema Naturae, in which he introduced many of the concepts and conventions that are still used by taxonomists today.

Biology - 1758

• Albrecht von Haller described the embryology of the chick; later supported preformation doctrine.

Biology - 1759

• Caspar Friedrich Wolff's Theoria Generationis proposed an epigenetic theory of development which was opposed to preformationism and laid the basis for modern embryology. Wolff applied the microscope to the study of animal embryology and remarked that "the particles which constitute all animal organs in their earliest inception are little globules, which may be distinguished under a microscope."

Biology - 1760

• John Hunter developed comparative approach to anatomy, also established museums of natural history.

Biology - 1760-90

• British livestock breeds were improved by a thirty-year program of selection and inbreeding undertaken by Robert Bakewell, Collings, Bates, and others.

Biology - 1761-66

• Joseph Gottlieb Kölreuter (Koelreuter) published reports describing 136 experiments in artificial hybridization. His discovery of quantitative inheritance foreshadowed the work of Mendel.

Biology - 1762

• Marcus Antonius Plenciz, in Opera medico-physica, formulated the view that infectious diseases were caused by a living agent.

Biology - 1763

• Michael Adanson advocated an empirical approach to taxonomy based on shared characters rather than evolutionary relationships.

Biology - 1764-74

• Charles Bonnet championed preformation doctrine.

Biology - 1766

• Henry Cavendish discovered "inflammable air" (hydrogen), which he concluded to be a combination of water and phlogiston, since its combustion yielded water.

Biology - 1766

• Leonhard Euler suggested a design for achromatic lenses.

Biology - 1766-84

• Controversy between John T. Needham and Lazarro Spallanzani over spontaneous generation.

Biology - 1770

• John Hill introduced new techniques for macerating, preserving and staining woody materials. He employed alum, alcohol and carmine in preparing specimens for microscopic study.

Biology - 1770-74

• Joseph Priestley discovered oxygen and showed that it is consumed by animals and produced by plants.

Biology - 1770-86

• Carl Wilhelm Scheele isolated citric, malic, lactic, and uric acids and glycerol from natural sources and produced oxygen from silver carbonate.

Biology - 1772

• Daniel Rutherford described "residual air". His is the first published description of what we now know as nitrogen.

Biology - 1772

• Joseph Priestley and Jan Ingenhousz investigated photosynthesis.

Biology - 1773

• Hillaire-Marin Rouelle isolated urea from urine.

Biology - 1773-86

• Otto Frederik Müller (Mueller) taxonomically separated bacteria from protozoa and was able to distinguish two distinct morphological types of bacteria: bacillum and spirillum.

Biology - 1774

• Joseph Priestley produced oxygen by heating mercuric oxide.

Biology - 1776

• Lazarro Spallanzani confirmed Antoni van Leeuwenhoek's descriptions of spermatozoa.

Biology - 1777

• Adair Crawford published the first experiments on animal calorimetry, comparing heat production in a guinea pig with combustion.

Biology - 1778

• Wilhelm Friedrich Von Gleichen-Russworm stained bacteria with indigo and carmine.

Biology - 1778

• Antoine Lavoisier demonstrated the nature of animal respiration.

Biology - 1779

• The peculiar inheritance of human color-blindness was reported to The Royal Society of London by M. Lort. Laws for inheritance of sex-linked traits were fully formulated 40 years later by Christian Friedrich Nasse.

Biology - 1779

• Johann Friedrich Blumenbach classified spermatozoa as Infusoria.

Biology - 1779

• Publication of Jan Ingenhousz's Experiments on Vegetables showing that illumination was required for oxygen production in plants. He also showed that plants use carbon dioxide.

Biology - 1780

• Lazarro Spallanzani performed experimental artificial fertilization in amphibians, silkmoth, and dog. Concluded from filtration experiments that spermatozoa were unnecessary for fertilization. Described cleavage in frog embryo.

Biology - 1780

• Antoine Lavoisier and Pierre Laplace published their memoir on heat, in which they reached the conclusion that respiration is a form of combustion.

Biology - 1780

• George Adams (the younger) and others devised slicing machines (microtomes) capable of cutting sections some 1/2000 of an inch thick.

Biology - 1781

• Peter Christian Abildgaard investigated the life cycle of a tapeworm and found that it required more than one host. This finding was not widely accepted until it was confirmed by Gottlob Küchenmeister 70 years later.

Biology - 1781

• Felice Fontana described the nucleolus after finding it in the slime from an eel's skin.

Biology - 1783

• Lazarro Spallanzani extended René Antoine de Réaumur's findings to other birds, small mammals, and finally to humans by using himself as an experimental animal. Digestion was clearly shown to be a chemical process rather than a mechanical grinding of the food.

Biology - 1788

• Jean Senebier showed that it is the light and not the heat of the sun that is effective in photosynthesis.

Biology - 1789

• Antoine Lavoisier published Traite Élémentaire de Chimie, in which fermentation is described as the splitting of sugar into alcohol and carbon dioxide. He characterized the reaction as an oxidation-reduction reaction. Lavoisier and Armand Séguin made the first measurements of human metabolic rate.

Biology - 1791

• William Smith pointed out the relationship between fossils and geologic strata. He worked out a method for estimating geologic age, and laid the foundation of stratigraphic geology.

Biology - 1792

• Controversy between Luigi Galvani and Alessandro Volta over the twitching of frogs' legs led to an interest in investigating the electrical phenomena of animals.

Biology - 1793

• Publication of Christian Konrad Sprengel's Das Entdeckte Geheimniss der Natur im Bau und in der Befruchtung der Blumen.

Biology - ????

• Publication of Christian Konrad Sprengel's Die nützlichkeit der bienen und die nothwendigkeit der bienenzucht, von einer neuen seite dargestellt.

Biology - 1794-96

• Erasmus Darwin's Zoönomia published; advanced the idea that environmental influences transformed species.

Biology - 1795

• James Hutton's Theory of the Earth published, interpreting certain geological strata as former sea beds.

Biology - 1795

• Lime and lemon juice were introduced into the British navy rations to control scurvy.

Biology - 1795

• Alexander Gordon demonstrates the contagiousness of puerperal fever.

Biology - 1796

• Jan Ingenhousz concluded that plants utilize carbon dioxide in their nutrition. He understood that plants carry on respiration concomitantly with photosynthesis.

Biology - 1796

• Edward Jenner used cowpox to vaccinate for smallpox.

Biology - 1796

• Baron Georges Cuvier attributed the succession of fossil forms to a series of simultaneous extinctions caused by natural catastrophes.

Biology - 1798

• Publication of Thomas Robert Malthus's Essay on the Principles of Population.

Biology - 1800

• Karl Friedrich Burdach coined the term "biology" to denote the study of human morphology, physiology and psychology.

Biology - 1801

• Jean Baptiste de Lamarck elaborated a theory of evolution based on heritable modification of organs through continued use and loss through disuse.

Biology - 1802

• Gottfried Treviranus and Jean Baptiste de Lamarck independently broadened the meaning of biology to include the study of all living things.

Biology - 1802

• Thomas Young proposes a trichromatic theory of color vision, based on three separate receptor substances in the retina.

Biology - 1802

• Charles François Brisseau de Mirbel concluded from his numerous observations of plant structure that "the plant is wholly formed of a continuous cellular membranous tissue. Plants are made up of cells, all parts of which are in continuity and form one and the same membranous tissue."

Biology - 1804

• Nicholas-Théodore de Saussure published experiments that represent the first treatment of the subject of photosynthesis using quantitative methods and modern chemical terminology. He developed the first balanced equation for the process.

Biology - 1804

• John Dalton enunciated his atomic theory.

Biology - 1805

• Baron Georges Cuvier published his Lesson in Comparative Anatomy, which introduced that subject.

Biology - 1805

• Ludolf Christian Treviranus asserted that spermatozoa were analogous to the pollen of plants.

Biology - 1806

• Louis Nicolas Vauquelin and Pierre Jean Robiquet first isolated an amino acid, asparagine, from asparagus.

Biology - 1807

• Bénédict Prévost showed that an organism was responsible for wheat bunt disease.

Biology - 1809

• Jean Baptiste de Lamarck investigated the microscopic structure of plants and animals. He remarked, "It has been recognized for a long time that the membranes which form the envelopes of the brain, of the nerves, of vessels, of all kinds of glands, of viscera, of muscles and their fibers, and even the skin of the body are in general the productions of cellular tissue. But no one, so far as I know, has yet perceived that cellular tissue is the general matrix of all organization and that without this tissue no living body would be able to exist, nor could it have been formed."

Biology - 1809

• Jean Baptiste de Lamarck's Philosophie Zoologique emphasized the fundamental unity of life and the capacity of species to vary; environmental influences stressed.

Biology - 1809

• Nicolas François Appert, a French chef, inventor and bacteriologist, demonstrated a procedure for preservation of foods by canning.

Biology - 1810

• William Hyde Wollaston isolated the second amino acid, cystine, from a bladderstone.

Biology - 1810

• Joseph Louis Gay-Lussac deduced the equation for alcoholic fermentation.

Biology - 1810

• Planche observed that extracts of plant roots would turn alcoholic solutions of guaiacum blue. The agent responsible for this change was found to be water-soluble and thermolabile.

Biology - 1811

• Amedo Avogadro proposed that a fixed number of molecules of any gas will equal the molecular weight of the gas in grams. This was not widely accepted until 1858.

Biology - 1811

• Charles Bell and François Magendie discover the functions of the dorsal and ventral roots of spinal nerves.

Biology - c. 1815

• Robert Brown distinguished angiosperms from gymnosperms in his classification of the higher plants.

Biology - 1815

• Konstantin Sigizmundovich (Gottleib Sigismund Constantin) Kirchhof reported that a glutinous component of wheat is capable of converting starch to dextrin and sugar.

Biology - 1815

• Jean-Baptiste Biot discovered optical activity.

Biology - 1817

• Christian Heinrich Pander first described the existence of three germ layers in chick embryos. The concept was later extended by Karl Ernst von Baer to include all vertebrates.

Biology - 1817

• William Smith's Stratigraphical System of Organized Fossils showed that certain strata have characteristic series of fossils.

Biology - 1819

• Adelbert de Chamisso introduced the concept of alternation of generations.

Biology - 1820

• Christian Friedrich Nasse formulated Nasse's law: hemophilia occurs only in males and is passed on by unaffected females.

Biology - 1822

• John Goss observed segregation of a recessive trait in peas, but failed to note numerical ratios. In the same year, Alexander Seton published similar observations.

Biology - 1822-26

• Étienne Geoffrey St. Hilaire experimentally produced abnormal development in chicks, providing an argument against preformation.

Biology - 1823

• Thomas Andrew Knight confirmed reports of dominance, recessivity, and segregation in peas, but did not detect regularities.

Biology - 1823

• Jean-Louis Prévost and Jean Baptiste André Dumas showed that urea is transported by the blood.

Biology - 1824

• Henry Hickman used carbon dioxide to anesthetize animals prior to surgery.

Biology - 1824

• Henri Dutrochet further advanced the cell principle. He stated, "All organic tissues are actually globular cells of exceeding smallness, which appear to be united only by simple adhesive forces; thus all tissues, all animal (and plant) organs, are actually only a cellular tissue variously modified. This uniformity of finer structure proves that organs actually differ among themselves merely in the nature of the substances contained in the vesicular cells of which they are composed."

Biology - 1824-25

• Jean-Louis Prévost and Jean Baptiste André Dumas repeated Lazarro Spallanzani's filtration experiments, thus confirming the necessity of spermatozoa for fertilization, and described cleavage in a frog egg.

Biology - 1826

• Pierre-Jean-François Turpin reported his observations of cell division in algae.

Biology - 1827

• Karl Ernst von Baer first demonstrated the mammalian ovum; he regarded the sperm cells as "Entozoa," i.e., parasites, and named them spermatozoa.

Biology - 1828

• Publication of Karl Ernst von Baer's The Embryology of Animals which strongly opposed preformationism.

Biology - 1828

• Friedrich Wöhler synthesized the first organic compound from inorganic components, preparing urea by reacting lead cyanate with ammonia.

Biology - 1828

• Robert Brown first described Brownian motion.

Biology - 1828

• John Vaughan Thompson first collected and described plankton. He also correctly described barnacles as crustaceans.

Biology - 1830

• Joseph Lister showed how lenses could be made which corrected for chromatic and sperical aberration. (This is not the same Joseph Lister who is known for antiseptic surgery.)

Biology - 1830

• Karl Ernst von Baer enunciated the biogenetic law.

Biology - 1830

• Franz Julius Ferdinand Meyen reported his observations on algae, fungi and higher plants and concluded that "...each cell forms an independent, isolated whole; it nourishes itself, builds itself up, and elaborates raw nutrient materials, which it takes up, into very different substances and structures."

Biology - 1830

• Pierre-Jean Robiquet and Boutron, also Chalard, discovered the hydrolytic splitting of amygdalin by an extract of defatted bitter almonds. The agent was named "emulsin" by Justus von Liebig and Friedrich Wöhler in 1837.

Biology - 1830

• Giovanni Battista Amici investigated the process of fertilization in plants and was able to trace the growth of the pollen tube through the style to the micropyle of the ovary.

Biology - 1830-33

• Charles Lyell's Principles of Geology advanced the theory of uniformitarianism, i.e., the view that geological formations were explainable in terms of forces and conditions observable at present.

Biology - 1830-40

• Justus von Liebig developed techniques of quantitative analysis and applied them to biological systems. The idea that vital activity could be explained in physicochemical terms was an important one for investigators interested in the nature of life.

Biology - 1831

• Robert Brown published his observations reporting the discovery and widespread occurrence of nuclei in cells.

Biology - 1831

• Leuchs described the diastatic action of salivary ptyalin.

Biology - 1831-1836

• The voyage of the Beagle, with Charles Darwin aboard as naturalist.

Biology - 1832

• Dumortier observed the process of cell division in algae.

Biology - 1833-1834

• Anselme Payen and Jean-François Persoz further described and isolated diastase (amylase) in powder form from barley malt, showed it to be heat labile, and postulated the central importance of enzymes in biology.

Biology - 1833

• Marshall Hall described the mechanism by which a stimulus can produce a response independently of sensation or volition and coined the term "reflex."

Biology - 1833

• Jan Evangelista Purkinje (Purkyne) discovered sweat glands. He later discovered the neurons in the cortex of the cerebellum and the conducting fibers in the heart which bear his name. He also studied visual perception and devised the first system for classifying fingerprints.

Biology - 1833

• Jean-Baptiste-Joseph-Dieudonné Boussingault recommended the use of iodized salt to cure goiter.

Biology - 1835

• Jöns Jacob Baron Berzelius demonstrated that the hydrolysis of starch is catalyzed more efficiently by malt diastase than by sulfuric acid and published the first general theory of chemical catalysis.

Biology - 1835

• Agostino Bassi demonstrated that a disease of silkworms was caused by a fungus. This discovery gave impetus to the germ theory of disease.

Biology - 1835

• Felix Dujardin associated the "sarcode" (protoplasm) of protozoa with life processes.

Biology - 1835

• Richard Owen discovered Trichinella.

Biology - 1835-38

• Peltier maintained spermatozoa to be differentiated body cells.

Biology - 1835-39

• Hugo von Mohl carefully described some details of mitosis in plants. He recorded the appearance of the cell plate between daughter cells. He remarked, "Cell division is everywhere easily and plainly seen...in terminal buds and root tips."

Biology - 1836

• Charles Giles Bridle Daubeny investigated the efficiency of different parts of the spectrum in photosynthesis.

Biology - 1836

• François Magendie demonstrated the need for dietetic nitrogen.

Biology - 1836

• Theodor Schwann reported the action of pepsin and described its properties. Putrefaction and fermentation were attributed to the action of micro-organisms.

Biology - 1836

• Christian Gottfried Ehrenberg discovered giant axons in the Crustacea.

Biology - 1836-37

• Frantz Schultze's and Theodor Schwann's experiments opposing spontaneous generation.

Biology - 1837

• Jöns Jacob Baron Berzelius classified fermentation as a catalyzed reaction. He later identified lactic acid as a product of muscle activity.

Biology - 1837

• René-Joachim-Henri Dutrochet recognized that chlorophyll was necessary for photosynthesis.

Biology - 1837

• Félix Dujardin asserted that the spermatozoa are produced in the seminiferous tubules of the testis.

Biology - 1837-38

• Charles Cagniard-Latour (Cagniard de la Tour) Theodor Schwann and Friedrich-Traugott Kützing independently announced that yeast was a living organism which was responsible for fermentation. This began the lengthy debate over whether fermentation was a chemical or a vital process.

Biology - 1838

• Matthias Jakob Schleiden published his Beiträge zur Phytogenese, an important contribution to understanding the genesis of plant tissues. He observed nucleoli but misinterpreted their significance in considering them as nuclei forming within nuclei. Theodor Schwann applied the same erroneous theory of cell formation to animal tissues but correctly emphasized that "cells are organisms and entire animals and plants aggregates of these organisms arranged according to definite laws."

Biology - 1838

• Christian Gottfried Ehrenberg separated bacteria from other micro-organisms.

Biology - 1838

• Gerardus Johannes Mulder carried out the first systematic studies of proteins. Mulder coined the term "protein".

Biology - 1839

• Jean-Baptiste-Joseph-Dieudonné Boussingault quantitatively studied the balance between the elementary constitution of the maintenance ration of a cow and that of the excretions and the milk.

Biology - 1839

• Justus von Liebig maintained that nonliving ferments cause fermentation. This began a controversy over whether fermentation was a vital or a chemical process.

Biology - 1839

• Peirre-François Verhulst developed the logistic model of population growth.

Biology - 1839-46

• Jan Evangelista Purkinje (Purkyne) proposed the term "protoplasm" for living matter and, together with Hugo von Mohl, established the protoplasm concept.

Biology - 1840

• Justus von Liebig proposed that fermentation is chemical and not dependent on living microbes.

Biology - 1840

• Jean-Pierre Lallemand held that the spermatozoa are produced in the seminiferous tubules.

Biology - 1840

• Martin Barry expressed the belief that the spermatozoon enters the egg.

Biology - 1840

• Publication of Justus von Liebig's Thierchemie which united the fields of chemistry and physiology.

Biology - 1840

• Johannes Müller established a theory of specific nerve energies.

Biology - 1840

• Justus von Liebig pointed out that organic compounds in plants are synthesized from carbon dioxide of the atmosphere while nitrogenous compounds are derived from precursors in the soil.

Biology - 1841

• Hugh Miller appraised the Devonian deposits of the Old Red Sandstone formation in Scotland, one of the most important vertebrate-bearing sediments ever discovered. Miller believed that the fossil record confirmed the biblical account of creation. He published Footprints of the Creator in 1847, and opposed evolution to his death in 1856.

Biology - 1841

• Albrecht von Kölliker (Koelliker) traced the histogenesis of the spermatozoa and proved that they are differentiated tissue cells.

Biology - 1842

• Julius Robert Mayer enunciated the first law of thermodynamics and its applicability to living organisms.

Biology - 1842

• William Bowman described the histologic structure of the nephron.

Biology - 1842

• Johann Japetus Steenstrup described the alternation of sexual and asexual generations in plants and animals.

Biology - 1843

• Oliver Wendell Holmes observed the contagiousness of septicemia.

Biology - 1843

• Richard Owen elaborated the distinction of homology and analogy.

Biology - 1843

• Justus von Liebig speculated that organic acids such as oxalic, tartaric, or malic were intermediates in the production of carbohydrates by plants.

Biology - 1844

• Charles Darwin made his first sketch of the theory of natural selection.

Biology - 1844

• Karl Ludwig showed that the Malpighian corpuscle of the kidney acts as a passive filter and that the waste products in the filtrate are concentrated as it passes through the tubules.

Biology - 1844

• John Dolland devised immersion microscopy.

Biology - 1844

• John William Draper showed that plants grown in solutions of sodium bicarbonate can liberate oxygen in the light.

Biology - 1845

• Herrmann von Helmholtz and Julius Robert Mayer formulated the laws of thermodynamics.

Biology - 1845

• Adolf Wilhelm Hermann Kolbe synthesized acetic acid, previously obtainable only as the result of vital activity. He later developed a method for the synthesis of salicylic acid.

Biology - 1845

• Carl Theodor Ernst von Siebold characterized Protozoa as "animals whose organization is reducible to one cell." Later, he discovered parthenogenesis in the honeybee.

Biology - 1845

• Miles Joseph Berkeley demonstrated that a mold was responsible for potato blight. He also made important contributions to the classification of fungi.

Biology - 1845

• Albrecht von Kölliker demonstrated that spermatozoa are cellular products of the organism. He also extended this finding to the ovum, from which the organism is derived by cell division.

Biology - 1846

• Pierre-Joseph van Benedin concluded that a cysticercus is an incomplete taenioid.

Biology - 1847-49

• Arnold Adolphe Berthold demonstrated by removal and transplantation that the testis produces a blood-borne substance conditioning sexual characteristics.

Biology - 1847-49

• Ignaz Semmelweis investigated the cause of puerperal fever.

Biology - 1848

• Wilhelm Hofmeister made sketches of microspore mother cells from Tradescantia which clearly show chromosomes in various stages of meiosis, but he failed to grasp their significance.

Biology - 1848

• Carl Theodor Ernst von Siebold established Protozoa as the basic phylum of the animal kingdom.

Biology - 1849

• Henri Victor Regnault and Jules Reiset published extensive comparative studies of respiration and calorimetry.

Biology - 1850-55

• Claude Bernard isolated glycogen from the liver, showed that it is converted into blood glucose, and discovered the process of gluconeogenesis.

Biology - 1851

• Augustus Volney Waller demonstrated that when nerve fibers are cut the distal portions of the fiber degenerate. This made it possible to trace the course of fibers through the nervous system and demonstrated the importance of the nucleus in the regeneration of fibers.

Biology - 1851-55

• Jean-Baptiste-Joseph-Dieudonné Boussingault demonstrated that higher plants cannot utilize atmospheric nitrogen, but only nitrates from the soil. He also demonstrated the necessity of nitrogen for plants and animals.

Biology - 1852

• Hermann von Helmholtz measured the speed of nervous impulses.

Biology - 1852

• Lucien Corvisart coined the term "tetany".

Biology - 1852

• Albrecht von Kölliker published first textbook of histology, Handbuch der Gewebelehre.

Biology - 1852

• Hermann Friedrich Stannius tied ligatures between the sinus venosus and the atrium, and between the atrium and the ventricles of a frog heart, and demonstrated that the sinus is the pacemaker of the heart, yet the atria and ventricles are capable of independent, spontaneous contractions.

Biology - 1852

• Gottlob Friedrich Heinrich Küchenmeister demonstrated that cysticerci (bladderworms) are the preadult forms of taeniid cestodes.

Biology - 1853

• George Newport observed the penetration of the vitelline membrane of the frog egg by the sperm.

Biology - 1854

• Heinrich Schröder (Schroeder) and Theodor von Dusch showed that bacteria could be removed from air by filtering it through cotton-wool.

Biology - 1854

• Louis Pasteur discovered microbial fermentation of beet sugar.

Biology - 1855

• Claude Bernard maintained that all organs liberated into the tissue fluids special substances which assisted in maintaining the constancy of the internal environment.

Biology - 1855

• Thomas Addison described the syndrome associated with the deterioration of the human adrenal cortex (Addison's disease). This is beyond question the first major achievement of clinical endocrinology.

Biology - 1856

• Nathanael Pringsheim observed sperm penetration of the egg of Oedogonium.

Biology - 1856

• Lucien Corvisart described trypsin, also used pepsin theraputically.

Biology - 1856

• The first of the aniline dyes, eosin, is synthesized. This dye would later prove useful for selectively staining cytoplasmic proteins.

Biology - 1856

• Edme-Félix-Alfred Vulpian applied a solution of ferric chloride to slices of the adrenal glands and noted that the medulla stained green while the cortex did not. He also noted that the same reaction was given by samples of venous blood leaving the adrenal, but not by arterial blood entering the gland. To account for these observations, he assumed that the medulla synthesized a substance that was liberated into the circulation.

Biology - 1856

• Carl Friedrich Wilhelm Ludwig develops perfusion techniques for keeping animal organs alive after their removal from the body. He also invented the kymograph, mercurial blood pump and a device for measuring the rate of blood flow. Ludwig was the first to study the role of the nervous system in blood flow and secretory function.

Biology - 1856

• Lord Kelvin (William Thomson) computed the age of the solar system as 25 million years (later revised to 40 million years).

Biology - 1856

• Discovery of the first Neanderthal remains.

Biology - 1857

• Albrecht von Kölliker discovered "sarcosomes" (mitochondria) in muscle cells.

Biology - 1857

• Claude Bernard demonstrated the formation of glycogen by the liver. This was the first demonstration of a catabolic process.

Biology - 1857

• Louis Pasteur demonstrated that lactic acid fermentation is carried out by living bacteria.

Biology - 1858

• Stanislao Cannizzaro demonstrated the validity of Avogadro's number.

Biology - 1858

• Louis Pasteur noted that Penicillium molds fermented only dextrotartaric acid and did not attack the levo isomer. Thus he developed a practical method for separating compounds which are identical except for the spatial arrangement of the substituent group.

Biology - 1858

• Carmine, a comercially available fabric stain, was found to stain cell nuclei more intensely than the cytoplasm.

Biology - 1858

• Rudolf Virchow applied the cell theory to problems of pathology and disease and set forth the illuminating principle that the outward symptoms of disease are merely the reflections of impairment at the level of cellular organization. He also advanced the notion that all cells arise from pre-existing cells: "Omnis cellula e cellula."

Biology - 1858

• Friedrich August Kekulé von Stradonitz proposes that carbon atoms can form chains.

Biology - 1858

• Philip Lutley Sclater studied the geographical distribution of birds.

Biology - 1858

• Joint announcement by Charles Darwin and Alfred Russell Wallace of the theory of natural selection.

Biology - 1859

• Publication of Charles Darwin's On the Origin of Species argued for natural selection as a factor in organic evolution. More importantly, it established evolution as an acceptable theory in the minds of most naturalists.

Biology - 1859

• Adolf Wilhelm Hermann Kolbe synthesized salicylic acid.

Biology - 1860

• Louis Pasteur states his aphorism, "Omne vivum e vivo."

Biology - 1860

• Alfred Russell Wallace claimed that a sharp boundary exists between the Australian and Oriental faunal regions. The "Wallace line of faunal delimitation" separated the Philippines from the Sanghir Islands and Borneo from Celebes, and ran through part of the Malay Archipelago.

Biology - 1861

• Jean Louis René Antoine Édouard Claparéde discovered giant axons in annelid worms.

Biology - 1861

• Thomas Graham's work on understanding the colloidal state of matter advanced the understanding of protoplasmic systems.

Biology - 1861

• Max Schultze established the protoplasm concept and, after noting the essential similarity between the cell contents of protozoa, plants and animals, concluded that "the cell is an accumulation of living substance or protoplasm definitely delimited in space and possessing a cell membrane and nucleus."

Biology - 1861

• Fossil remains of Archaeopteryx lithographica found in jurassic limestone deposits in a stone quarry in Solnhofen, Germany.

Biology - 1862

• Julius von Sachs produced experimental evidence that starch was a product of photosynthesis.

Biology - 1862

• Max Joseph von Pettenkofer devised an apparatus for analyzing respiratory gas exchange, thus making possible indirect calorimetry by the determination of respiratory quotients.

Biology - 1862

• Danielewski experimentally separated trypsin from pancreatic amylase by differential adsorption.

Biology - 1862

• Henry Walter Bates observed mimicry of distasteful or poisonous species by harmless, palatable species in the lepidoptera and suggests that the mimics enjoy protection from predation because of their resemblance.

Biology - 1863

• Karl Remigius Fresenius first used a solid culture medium (potato) for micro-organisms.

Biology - 1864

• Ernst Haeckel (Häckel) outlines the essential elements of modern zoological classification.

Biology - 1864

• Max Schultze observed plasmodesmata.

Biology - 1864

• Louis Pasteur's demolition of the doctrine of spontaneous generation.

Biology - 1864

• Controversy between Carl Nägeli and Robert Koch regarding pleomorphism versus genetic distinctness of bacteria.

Biology - 1864

• Ernst Felix Emmanuel Hoppe-Seyler performed the first crystallization of a protein: hemoglobin.

Biology - 1865

• Baron Joseph Lister instituted the practice of antiseptic surgery and the use of carbolic acid as a disinfectant.

Biology - 1865

• Friedrich August Kekulé von Stradonitz devises a ring model for the structural formula of benzene, supposedly after dreaming about six monkeys holding one another by the tail.

Biology - 1865

• The stain hematoxylin was found to stain cell nuclei more strongly than their cytoplasm.

Biology - 1866

• Gregor Mendel published his investigations of plant hybrids and their subsequent behavior. His fundamental discoveries lay forgotten for 34 years.

Biology - 1866

• Max Schultze discovered the existence of two types of receptor cells in the retina.

Biology - 1866

• Ernst Heinrich Haeckel (Häckel) hypothesizes that the nucleus of a cell transmits its hereditary information.

Biology - 1866

• Ernst Heinrich Haeckel (Häckel) first used the term "ecology" to describe the study of living organisms and their interactions with other organisms and with their environment.

Biology - 1866

• Aleksandr Onufriyevich Kovalevsky demonstrated the similarity between Amphioxus and the larval stages of tunicates and established the chordate status of the tunicates.

Biology - 1867

• Aleksandr Onufriyevich Kovalevsky extended the germ layer concept of Christian Heinrich Pander and Karl Ernst von Baer to include the invertebrates, establishing an important embryologic unity in the animal kingdom.

Biology - 1867

• Joseph Lister reported his method of antiseptic surgery.

Biology - 1868

• Charles Darwin elaborated the theory of pangenesis and gave it its name.

Biology - 1868

• Herrmann von Helmholtz proposed the resonance theory of hearing.

Biology - 1868

• Jean-Baptiste-Joseph-Dieudonné Boussingault pointed out that plants require oxygen for photosynthesis.

Biology - 1869

• Paul Langerhans, studying the structure of the pancreas, noted specialized groups or islands of cells that were especially well supplied with microscopic blood vessels.

Biology - 1870

• Justus von Liebig proposed that all ferments were chemical reactions rather than vital processes.

Biology - 1871

• Johann Friedrich Miescher isolated a substance which he called "nuclein" from the nuclei of white blood cells that was soluble in alkalis but not in acids. This substance came to be known as nucleic acid. Miescher also discovered that the amount of carbon dioxide in the blood affects the respiratory rate.

Biology - 1871

• Louis Pasteur conclusively demonstrated that yeast was necessary for fermentation as it could then be carried out. He distinguished two kinds of ferments, "organized ferments" such as yeast or lactic acid bacteria, and "unorganized ferments" like pepsin and amylase.

Biology - 1871

• Fagge concluded that degeneration, atrophy, or loss of the thyroid gland resulted in cretinism.

Biology - 1871

• Lambert Adolphe Jacques Quetelet showed the importance of statistical analysis for biologists and laid the foundation of biometry.

Biology - 1871

• Publication of Charles Darwin's Descent of Man, in which the role of sexual selection in evolution is described for the first time.

Biology - 1872

• C. Ore used chloral hydrate as an intravenous anesthetic.

Biology - 1872

• Ferdinand Julius Cohn coined the term "bacterium" and founded the study of bacteriology.

Biology - 1872

• Carl Friedrich Wilhelm Ludwig and Eduard Friedrich Wilhelm Pflüger studied the processes of gas exchange in the blood and showed that oxidation occurs in the tissues rather than in the blood.

Biology - 1872

• Anton Dohrn established the Naples Biological Station.

Biology - 1872-76

• The Challenger expedition greatly extended knowledge of the extent and variety of marine life.

Biology - 1873

• Anton Schneider observed and described the behavior of nuclear filaments (chromosomes) during cell division in his study of the platyhelminth Mesostoma. His account was the first accurate description of the process of mitosis in animal cells.

Biology - 1874

• Sir William Withey Gull recognized and described the disease known as Gull's disease--myxoedema with the atrophy of the thyroid gland--which he regarded correctly as the adult form of cretinism.

Biology - 1874

• Wilhelm His in Über unsere Körperform suggested mechanical explanations for morphological changes in the embryo.

Biology - 1874

• Ernst Haeckel (Häckel) established the taxonomic position of the Chordata, and proposed the "Gastrea" as the hypothetical ancestor to all metazoa.

Biology - 1875

• Oscar Hertwig showed that the head of the spermatozoon becomes a pronucleus and combines with the female pronucleus as the zygote nucleus and established the concept that fertilization is the conjugation of two cells.

Biology - 1875

• Eduard Strasburger accurately described the processes of mitotic cell division.

Biology - 1876

• Hans Buchner reported the reversible transformation of anthrax bacillus into hay bacillus. It isn't known whether he made an error in identification or simply used impure cultures.

Biology - 1876

• Ferdinand Julius Cohn studied the formation of spores in Bacillus subtilis. Cohn also assisted Robert Koch in his work on anthrax.

Biology - 1876

• Robert Koch showed that anthrax was caused by a specific organism. Koch's postulates for proving that a particular micro-organism is the cause of a particular disease greatly advanced the Germ Theory of Disease. They are still used today in slightly modified form.

Biology - 1877

• Wilhelm Friedrich Kühne proposed the term enzyme (meaning "in yeast") and distinguished enzymes from the micro-organisms that produce them.

Biology - 1877

• Gabriel Madeleine Camille Dareste described the successful production of developmental monstrosities by experimental means.

Biology - 1878

• Ernst Abbe, of the Zeiss Optical Works, developed the first oil-immersion objective microscope lens.

Biology - 1878

• Francis Maitland Balfour observed that the medullary region of the adrenal gland was derived from ectodermal rudiments that also gave rise to parts of the sympathetic nervous system, while the cortex arose from mesodermal buds.

Biology - 1879-82

• Walther Flemming described and named "chromatin," "mitosis" and the "spireme", made the first accurate counts of chromosome numbers and accurately figured the "longitudinal splitting" of chromosomes.

Biology - 1879

• Union of the gamete nuclei in syngamy was reported by Hermann Fol in an animal and by Fredrick Schmitz in a plant.

Biology - 1879

• Albrecht Kossel isolated nucleoproteins from the heads of fish sperm cells.

Biology - 1880

• Charles and Francis Darwin showed that a phototropic "influence" is transmitted from the tip of a unilaterally illuminated plant to the basal regions.

Biology - 1880

• Alphonse Laveran demonstrated that the causative agent in malaria is a protozoan.

Biology - 1880

• Sydney Ringer investigated the influence of inorganic ions on heart contraction, making possible an analysis of heart metabolism and the replacement of body fluids. Developed Ringer's solutions for the perfusion of isolated tissues. Studied the use of body temperature as a diagnostic indicator.

Biology - 1880-90

• Walther Flemming, Eduard Strasburger, Edouard van Beneden, and others elucidated the essential facts of cell division and stressed the importance of the qualitative and quantitative equality of chromosome distribution to daughter cells.

Biology - 1881

• Louis Pasteur gave a public demonstration of the effectiveness of his anthrax vaccine.

Biology - 1882

• Élie Metchnikoff studied the role of phagocytosis in the immune systems of starfish and Daphnia.

Biology - 1882

• Takaki reduced the incidence of beriberi in the Japanese navy by dietary improvements.

Biology - 1882

• Wilhelm Theodor Engelmann discovered that red light was the most effective in photosynthesis. His experimental method was one of the most elegant ever conceived.

Biology - 1882

• Robert Koch announced his method for isolating bacteria in pure culture by plating them on solid media (first gelatin, later agar).

Biology - 1882

• Eduard Strasburger coined the terms "cytoplasm" and "nucleoplasm."

Biology - 1882

• The Albatross, Under the direction of the U. S. Fish Commission, further extended knowledge of the extent and variety of marine life.

Biology - 1883

• Camillo Golgi and Santiago Ramon y Cajal developed and refined the silver nitrate technique to give a completely new picture of the intricate relationships between neurons.

Biology - 1883

• Max Rubner discovered that metabolic rate is proportional to the surface area of the body.

Biology - 1883

• Pierre Émile Duclaux introduced the custom of designating an enzyme by the by the name of the substrate on which its action was first reported and adding the suffix "- ase".

Biology - 1883

• Edouard van Beneden announced the principles of genetic continuity of chromosomes and reported the occurrence of chromosome reduction at germ cell formation. The sperm and egg are haploid and fertilization restores the diploid chromosome number.

Biology - 1883

• Wilhelm Roux described the time of determination of the main axes of the frog embryo. In the same year he correctly theorized the role of chromosomes in heredity.

Biology - 1883

• Oscar Hertwig originated the term "mesenchyme," a protoplasmic network filled with a fluid intercellular substance. It may be derived from all three germ layers, but is primarily mesodermal in origin, and gives rise to a variety of tissues: primarily connective tissue.

Biology - 1883

• Karl Georg Friedrich Rudolf Leuckart and A. P. Thomas independently worked out the life cycle of sheep liver flukes in detail. This was the first time that the complexity of the life cycle of these organisms, including its use of snails as intermediate hosts, was understood.

Biology - 1883

• Wilhelm Theodor Engelmann discovered photosynthesis in purple bacteria.

Biology - 1884

• Christian Joachim Gram invented his staining method for the classification of bacteria.

Biology - 1884

• Élie Metchnikoff proposed the cellular theory of immunity.

Biology - 1884

• Eduard Friedrich Wilhelm Pflüger, by allowing frog eggs to cleave under pressure, showed that abnormal cleavage patterns do not preclude formation of a normal embryo.

Biology - 1884

• Walther Flemming, Eduard Strasburger and Edouard van Beneden demonstrated that chromosome doubling occurs by a process of longitudinal splitting. Strasburger described and named the prophase, metaphase and anaphase stages of chromosomal division.

Biology - 1884

• Max Rubner extended the work of Justus von Liebig by making quantitative determinations of the energy values of certain foods. His work made possible a scientific explanation for metabolism and a basis for the study of comparative nutrition.

Biology - 1884

• Julius Kollman described the phenomenon of neoteny as observed in the axolotl form of Ambystoma tigrinum.

Biology - 1884

• Svante Arrhenius and Friedrich W. Ostwald independently defined acids as substances which release hydrogen ions when dissolved in water to become negatively charged ions highly capable of reacting with other compounds.

Biology - 1884-88

• Identification of the cell nucleus as the basis for inheritance was independently reported by Oscar Hertwig, Eduard Strasburger, Albrecht von Kölliker, and August Weismann.

Biology - 1885

• Karl Rabl theorized the individuality of chromosomes in all stages of the cell cycle.

Biology - 1885

• Walther Flemming observed sister chromatids passing to opposite poles of the cell during mitosis.

Biology - 1885

• Louis Pasteur treated Joseph Meister for rabies.

Biology - 1885

• Emil Christian Hansen instituted pure culture starters in the fermentation of beer.

Biology - 1885

• Wilhelm Roux formulated the mosaic theory of development after his work on early development in frog eggs.

Biology - 1885

• August Weismann formulated the germ plasm theory which held that the germ plasm was separate from the somatoplasm and was continuous from generation to generation.

Biology - 1886

• Ernst Abbe, of the Zeiss Optical Works, developed the apochromatic microscope lens.

Biology - 1886

• C. A. MacMunn discovered histohematins, later renamed cytochromes.

Biology - 1886

• Francis Galton devised a new useful statistical tool, the correlation table.

Biology - 1886

• Sir Victor Alexander Haden Horsley induced both cretinism and myxoedema in monkeys by experimentally removing the thyroid gland.

Biology - 1886

• Pierre Marie fully described the constellation of symptoms termed acromegaly.

Biology - 1886

• The Woods Hole Biological Station was established.

Biology - 1887

• Oscar Minkowski associated acromegaly with a hyperfunctional pituitary gland.

Biology - 1887

• August Weismann elaborated an all-encompassing theory of chromosome behavior during cell division and fertilization and predicted the occurrence of meiosis. Wilhelm Roux put forth the suggestion that the linearly arranged qualities of the chromosomes were equally transmitted to both daughter cells at meiosis.

Biology - 1887

• Edouard van Beneden demonstrated chromosome reduction in gamete maturation, thereby confirming August Weismann's predictions.

Biology - 1887

• George Henry Falconer Nuttall and Josef Fodor found that blood from an animal that had been exposed to anthrax hindered the growth of anthrax bacilli.

Biology - 1887

• Emil Fischer elaborated the structural patterns of proteins.

Biology - 1887

• Ernst Haeckel (Häckel), after studying the radiolarians brought back from the Challenger expedition and elaborated the concept of organic form and symmetry.

Biology - 1887-1904

• Zuntz, Geppert, Wilbur Olin Atwater, and others perfected instruments and techniques for indirect calorimetry.

Biology - 1888

• Wilhelm Roux's experimental production of a half-embryo by killing one blastomere of the two-celled frog embryo.

Biology - 1888

• Theodor Boveri verified August Weismann's predictions of chromosome reduction by direct observation in Ascaris.

Biology - 1888

• Heinrich Wilhelm Gottfried Waldeyer named the chromosome.

Biology - 1889

• Francis Galton formulated the law of ancestral inheritance, a statistical description of the relative contributions to heredity made by one's ancestors.

Biology - 1889

• Charles Edward Brown-Séquard injected macerated testes from other animals into his own body and believed he obtained rejuvenating effects. Though erroneous, these conclusions were influential in inaugurating the administration of endocrine gland extracts as an experimental technique.

Biology - 1889

• Richard Hertwig and Emile Maupas independently demonstrated exchange of micronuclei in conjugation by Paramecium.

Biology - 1889

• Baron Joseph von Mering and Oscar Minkowski duplicated the symptoms of diabetes in the dog by experimental excision of the pancreas. They obtained further presumptive evidence for the endocrine function of the islets of Langerhans in 1893.

Biology - 1890

• Richard Altmann described procedures for staining mitochondria, studied their distribution, and postulated them to have metabolic and genetic autonomy.

Biology - 1890

• The numerical equality of paternal and maternal chromosomes at fertilization was established by Theodor Boveri in Germany and Jean-Louis-Léon Guignard in France.

Biology - 1890

• Theobald Smith first demonstrated the transmission of a disease by an arthropod vector: the infection of cattle with the sporozoan Babesia by the tick Boophilus.

Biology - 1890

• Emil Adolf von Behring discovered antibodies.

Biology - 1991

• Heinrich Wilhelm Gottfried Waldeyer proposed the neuron theory of the nervous system.

Biology - 1991

• Hans Buchner proposes the existence of antibacterial proteins in blood serum which he called "alexines". This began a protracted debate with Metchnikoff, who championed a cellular theory of immunity.

Biology - 1891

• George Redmayne Murray prepared emulsions of dried sheep thyroid in glycerine. He used these with considerable success on patients suffering from hypothyroidism.

Biology - 1891

• Hans Dreisch discovered that each of the first several blastomeres of the sea urchin egg would, after being separated by shaking, develop into a complete embryo. Dreisch's theory of totipotency contradicted Wilhelm Roux's mosaic theory.

Biology - 1891

• Marie Eugene François Thomas Dubois discovered Java man and named it Pithecanthropus erectus, now known as Homo erectus.

Biology - 1892

• Dmitri Iosifovich Ivanovski discovered a disease-causing agent smaller than bacteria: viruses.

Biology - 1892

• Publication of August Weismann's book Das Keimplasma (The Germ Plasm) emphasized meiosis as an exact mechanism of chromosome distribution.

Biology - 1893

• Oscar Hertwig obtained twin embryos in the newt by constricting the egg.

Biology - 1893

• Wilhelm Ostwald proved enzymes are catalysts.

Biology - 1893

• Louis Antoine Marie Joseph Dollo pointed out the irreversibility of evolution.

Biology - 1893

• Wilhelm His investigated the specialized conducting tissue of the atrioventricular node and bundle of the heart.

Biology - 1894

• Hans Dreisch expounded the view that all nuclei of an organism were equipotential but varied in their activity in accordance with the differentiation of tissues.

Biology - 1894

• William Bateson's Materials for the Study of Variation emphasized the importance of discontinuous variations, foreshadowing the rediscovery of Mendel's work.

Biology - 1894

• Karl Pearson published the first in a long series of contributions to the mathematical theory of evolution. Methods for analyzing statistical frequency distributions were developed in detail.

Biology - 1894

• Emil Fischer conducted an extensive series of investigations which still form the basis for our notions of enzyme specificity.

Biology - 1894

• Conway Lloyd Morgan established the basic principles in the study of animal behavior including his famous canon which stated that the actions of an animal should be interpreted in terms of the simplest mental processes.

Biology - 1894

• William Maddock Bayliss and Ernest Henry Starling studied electric currents in the mammalian heart.

Biology - 1894

• George Oliver and Edward Albert Sharpey-Schäfer (Schaefer) first demonstrated the action of a specific hormone: the effect of an extract of the adrenal gland on blood vessels and muscle contraction.Upon injection into normal animals it produced a striking elevation in blood pressure.

Biology - 1894-97

• Born made heteroplastic grafts of parts of frog and toad embryos.

Biology - 1895

• Wilhelm Roux's Archiv für Entwicklungsmechanik der Organismen was founded.

Biology - 1895

• David Bruce investigated the life cycle of the protistan blood parasite Trypanosoma and the role of the tse-tse fly in its transmission.

Biology - 1895

• Wilhelm Konrad Röntgen (Roentgen) discovered x-rays, which were soon to be applied in the visualization of bodily structures and in the induction of genetic mutations (both intentionally and accidentally).

Biology - 1895

• Adolf Magnus-Levy found by means of direct calorimetric measurements that persons with myxoedema have a lowered heat production. He also found that administration of thyroid preparations to normal or myxoedemic patients raised the metabolic level.

Biology - 1895

• Theobald Smith produced a hemorrhagic deficiency disease in guinea pigs deprived of leafy foods.

Biology - 1896

• James Mark Baldwin elaborated the Baldwin effect, which is the belief that selection of genotypes will be channeled in the same direction as nonhereditary adaptive modifications.

Biology - 1896

• The Russian Hydrographic Survey of the Biology of Lake Baikal was undertaken. This survey found several unique endemic freshwater animals that have become extinct in the rest of the world.

Biology - 1896

• Eugen Baumann reported that the thyroid contained an appreciable concentration of iodine in organic combinations. He also reported that persons inhabiting coastal areas contained more thyroid iodine than persons living further inland.

Biology - 1896

• Herbert Edward Durham and Max von Gruber discovered specific agglutination, and Fernand Isidore Widal found that blood serum from a typhoid patient would agglutinate typhoid bacilli, thus introducing the process of serologic diagnosis.

Biology - 1897

• Christiaan Eijkman produced experimental polyneuritis in chickens by feeding them polished rice, and called attention to rice hulls as containing the preventive agent of human beriberi. This work identified the first known vitamin deficiency disease.

Biology - 1897

• Wilhelm Ostwald clearly demonstrated that the iodine of the thyroid is firmly bound to a globulin-like protein and introduced the term thyroglobulin.

Biology - 1897

• Oscar Hertwig centrifuged frog eggs and demonstrated the effect of yolk distribution on cleavage.

Biology - 1897

• Karl Ferdinand Braun invented the oscilloscope.

Biology - 1897

• Eduard Buchner resolved the Liebig-Pasteur controversy by producing fermentation in cell-free yeast extracts containing zymase. Although he demonstrated that living yeast cells were not necessary for fermentation, this in no way proved that Liebig's proposed mechanism was correct.

Biology - 1897

• Gabriel Bertrand coined the term "coenzyme" to designate inorganic substances which were necessary to activate certain enzymes.

Biology - 1897

• John Jacob Abel and A. C. Crawford isolated the first hormone, later named epinephrine by Jokichl Takamine.

Biology - 1897

• The Canadian Geological Survey found rich fossil beds containing Upper Cretaceous dinosaur fauna along the Red Deer River in Alberta.

Biology - 1897

• A. Huot discovered that some fish have aglomerular kidneys, proving that renal tubules can secrete and resorb substances.

Biology - 1897

• Ronald Ross elucidated the life-cycle of Plasmodium.

Biology - 1897

• Sir Charles Scott Sherrington deduced the existence of synapses by showing that individual nerve cells could exert integrative influences on other nerve cells by graded excitatory or inhibitory synaptic actions.

Biology - 1898

• C. Benda and Camillo Golgi described mitochondria and Golgi bodies in great detail and named them. The Golgi apparatus was first observed in 1855, but Golgi's silver nitrate impregnation method made more detailed observation of this important inclusion possible in the nerve cells he studied.

Biology - 1898

• Croft-Hill announced the first enzymatic synthesis, that of isomaltose.

Biology - 1898

• Charles Reid Barnes proposed the term "photosynthesis."

Biology - 1898

• Double fertilization in plants was described by Sergey Gavrilovich Navashin.

Biology - 1898

• Walther Flemming determined chromosome number as 24 pairs in man.

Biology - 1898

• Henry Fairfield Osborn enunciated the concept of adaptive radiation in evolution.

Biology - 1898-1904

• Walter Bradford Cannon used x-rays to study the movements of the digestive system.

Biology - 1899

• William Bate Hardy pointed out that many of the appearances of cytoplasm were artifacts of the staining and fixing methods that were employed; therefore, the existence of cytoplasmic structures should be confirmed by alternative methods.

Biology - 1899

• The First International Congress of Genetics held in London.

Biology - 1899

• The German chemical firm of Beyer introduced acetylsalicylic acid under the name "Aspirin".

Biology - 1899

• Richard Altmann renamed "nuclein" "nucleic acid".

Biology - 1900

• Hugo DeVries (Holland), Karl Correns (Germany), and Erich von Tschermak-Seysenegg (Austria) claimed to have independently discovered and verified Gregor Mendel's principles, marking the beginning of modern genetics.

Biology - 1900-01

• The Yellow Fever Commission, led by Walter Reed, investigated the transmission of yellow fever in Havana, Cuba.

Biology - 1900

• Curt Herbst used calcium-free sea water to separate blastomeres of the sea urchin.

Biology - 1900

• Charles William Andrews discovered numerous early higher primate remains in the Fayum Depression region east of Cairo, Egypt.

Biology - 1900

• T. C. Chaimberlain theorized the freshwater origin of the vertebrates based on the discovery of early vertebrate fossils in the Old Red Sandstone deposits, which he believed to have had a freshwater origin.

Biology - 1900

• Karl Landsteiner discovered the A, B and O blood groups in man.

Biology - 1900

• Jacques Loeb induced artificial parthenogenesis in frog and sea urchin eggs by mechanically stimulating them.

Biology - 1901

• Friedel found that powdered leaves can liberate oxygen when resuspended and illuminated.

Biology - 1901

• T. B. Aldrich and Jokichl Takamine isolated a substance with hormone activity from the adrenal medulla and named it "epinephrine".

Biology - 1901

• Hermann Henking and others reported an "accessory chromosome" in spermatozoa, later identified as the sex chromosome.

Biology - 1901

• Thomas Harrison Montgomery Jr. noticed the homologous pairing of maternal and paternal chromosomes at synapsis prior to the reductive division.

Biology - 1901

• Franz Hofmeister articulates his enzyme theory of life: for every vital reaction there is a specific enzyme responsible. This view shortly became widely accepted.

Biology - 1901-03

• Hugo De Vries's Mutationslehre advanced the thesis that species are not continuously connected but arise through sudden large changes.

Biology - 1901-03

• Hans Spemann performed constriction experiments on newt eggs.

Biology - 1901-04

• George Henry Falconer Nuttall investigated the serological relationships of animals by the precipitin reaction.

Biology - 1902

• Karl Landsteiner discovered the AB blood group.

Biology - 1902

• Clarence Erwin McClung theorized that certain chromosomes whose synaptic mates were different in appearance or entirely absent, e. g. Hermann Henking's accessory chromosomes, were responsible for sex determination.

Biology - 1902

• Emil Fischer and Franz Hofmeister demonstrated that proteins are polypeptides.

Biology - 1902

• William Bateson coined the terms F1, F2, allelomorphism, homozygote, and heterozygote. He also listed some 26 different cases of established allelomorphism in wheat, maize, peas, snapdragon, Datura, Oenothera, mouse, cattle, fowl, and man.

Biology - 1902

• Charles Robert Richet investigated anaphylaxis and gave it its name.

Biology - 1902-03

• William Maddock Bayliss and Ernest Henry Starling discovered secretin, a hormone produced by the intestinal mucosa which acted principally on the pancreas.

Biology - 1902-03

• Walter Stanborough Sutton and Theodor Boveri pointed out the parallelism between chromosome behavior and Mendelism, closing the gap between cytology and heredity.

Biology - 1903

• The concepts of phenotype, genotype and selection were introduced and clearly defined by Wilhelm Ludwig Johannsen.

Biology - 1903

• Wilhelm Roux showed that the point of entrance of the sperm marks the future mid-ventral line of the frog.

Biology - 1903

• Carl Neuberg first used the term biochemistry.

Biology - 1904

• Ross Granville Harrison obtained experimental induction of the lens by transplanting the optic cup.

Biology - 1904

• Stoltz determined the chemical formula for epinephrine and achieved a total chemical synthesis of the substance.

Biology - 1904

• Herbert Spencer Jennings studied the orientation behavior of the Protozoa.

Biology - 1904-05

• Sir Arthur Harden and W. J. Young isolated the first organic coenzyme: cozymase. They clearly demonstrated that fermentation required the simultaneous presence of both a colloidal heat labile fraction and a diffusible, low molecular weight, heat stable coenzyme, later found to be NAD. They also demonstrated the necessity of phosphate in alcoholic fermentation by zymase.

Biology - 1905

• George Henry Falconer Nuttall demonstrated the importance of intestinal bacteria in digestion.

Biology - 1905

• Ernest Henry Starling introduced the word hormone.

Biology - 1905

• F. Knoop deduced the beta-oxidation of fatty acids.

Biology - 1905

• Frederick Frost Blackman published Optima and Limiting Factors, in which he applied physicochemical ideas to biological problems. He pointed out that photosynthesis involved several processes, its rate being determined by several possible limiting factors.

Biology - 1905

• John Scott Haldane and John Gillies Priestly investigated the role of carbon dioxide in the regulation of breathing.

Biology - 1905

• Lucien Claude Cuénot discovered the first lethal allele: the yellow coat color allele in mice.

Biology - 1905

• Richard Adolf Zsigmondy applied the centrifuge to the study of colloids, making a more detailed understanding of protoplasmic constituents possible.

Biology - 1905

• N. M. Stevens and Edmund Beecher Wilson extended the findings of cytology to the interpretation of sex determination.

Biology - 1905

• William Bateson and Reginald Crundall Punnett reported the discovery of two new genetic principles: linkage and gene interaction.

Biology - 1906

• Woodworth and William Ernest Castle introduced Drosophila as new experimental material for genetic studies.

Biology - 1906

• Christiaan Eijkman found the anti-beriberi agent to be a water-soluble component of rice polishings.

Biology - 1906

• Sir Fredrick Gowland Hopkins first sought to explain dietary deficiency by a biochemical investigation of the lack of essential amino acids in the diet.

Biology - 1906

• Willem Einthoven invented the electrocardiogram.

Biology - 1906

• Tawara discovered the atrioventricular node of the heart.

Biology - 1906

• Mikhail Semenovitch Tswett (Tsvett) first used the technique of chromatography. He used the technique to separate plant pigments: hence, its name.

Biology - 1906-16

• The Yellow Fever Commission, led by William Gorgas effectively eliminated malaria and yellow fever in the Panama Canal Zone by eradicating the Aëdes and Anopheles mosquitoes.

Biology - 1906-26

• Richard Willstätter and coworkers discovered the chemical structure of the chlorophyll pigments.

Biology - 1907

• Sir Arthur Keith and M. J. Flack discovered the sinoatrial node of the heart and recognized is role as the heart's pacemaker.

Biology - 1907

• Sir Walter Morley Fletcher and Sir Fredrick Gowland Hopkins showed that lactic acid is formed quantitatively from glucose during anaerobic muscle contraction. Hopkins also showed that part of the lactic acid is oxidized to furnish energy for the synthesis of glycogen from the remaining lactic acid.

Biology - 1907

• H. V. Wilson convincingly demonstrated the high level of cell individuality in phenomena of coalescence and regeneration in sponges.

Biology - 1907

• Ross Granville Harrison developed new techniques for culturing and studying isolated cell or tissue fragments apart from the intact whole organism.

Biology - 1907

• Lutz proved that the gigas mutation in the evening primrose contained twice the usual chromosome number. This led to the analysis and artificial production of polyploidy.

Biology - 1907

• Bertram Borden Boltwood first proposed the use of radioactivity data to determine the age of minerals.

Biology - 1907

• Theodor Boveri demonstrated that the chromosomes have qualitatively different effects on development by removing individual chromosomes from developing sea urchin eggs. Only those cells that contained a full complement of chromosomes developed normally.

Biology - 1907

• Otto Schoetensack discovered the mandible of a primitive hominid in a sandpit in Mauer, Germany. This specimen has been referred to as "Heidelberg Man" and is a less archaic form of Homo erectus than Java Man.

Biology - 1907-17

• Charles Rupert Stockard studied the effects of chemicals on embryologic development and produced cyclopia and other monstrosities by the use of lithium and other agents.

Biology - 1908

• Heribert Nilsson-Ehle Analyzed the inheritance of color in wheat and provided a useful model for the further analysis of continuously variable characters.

Biology - 1908

• Archibald Edward Garrod recognized that gene products are proteins. He also was the first to carry out detailed studies of genetic diseases in humans. His work was largely ignored until 1940.

Biology - 1908

• Godfrey Harold Hardy, a Cambridge mathematician, and Wilhelm Weinberg, a Stuttgart physician, independently formulated the theorem that in the absence of mutation and selection, the frequency of a gene in any large, randomly mating population will reach an equilibrium in one generation and remain in equilibrium thereafter regardless of whether the gene is dominant or recessive. Also, the genotypic frequencies of a population in equilibrium with two alleles with frequencies p and q are given by the formula p2 + 2pq + q2. This theorem forms the mathematical basis for population genetics.

Biology - 1909

• Wilhelm Johannsen demonstrated that natural selection could not act on genetically pure lines but can only isolate existing genotypes. Therefore, natural selection can only influence evolutionary change if there is a source of genetic variability. Johannsen also was the first to use the terms "genotype" and "phenotype".

Biology - 1909

• William Ernest Castle and John Charles Phillips transplanted an ovary from a black guinea pig into a white one and showed that it would still produce black offspring if mated to a black male. This was intended to show that the hereditary characteristics of germ cells is unaffected by somatic influences.

Biology - 1909

• F. A. Janssens suggested that the chiasmata observed between synaptic chromosomes could be taken as observational evidence for the phenomenon of crossing over among linked genes, although he could not prove it.

Biology - 1909

• Rollins Adams Emerson discovered multiple allelomorphism in corn and also in beans.

Biology - 1909

• Svante Arrhenius and Søren Sørensen showed that the hydrogen ion concentration in a solution could be experimentally determined. Sørensen pointed out the effect of pH on enzyme activity.

Biology - 1909

• Charles Jules Henri Nicolle demonstrated that typhus fever was transmitted by the body louse.

Biology - 1909

• Jean Eugene Bataillon discovered the phenomenon of pseudogamy.

Biology - 1910

• James Bryan Herrick discovered sickle cell anemia

Biology - 1910

• P. Boysen-Jensen established the existence of phytohormones or auxins which were responsible for the chemical transmission of growth responses of higher plants. He demonstrated that the phototropic influence is material, since it can cross an incision, but cannot pass through a mica barrier.

Biology - 1910

• Ivan Petrovitch Pavlov discovered classical conditioning, and Oskar Heinroth discovered imprinting behavior.

Biology - 1910

• John Murray and Johan Hjort led the Michael Sars deep-sea expedition.

Biology - 1910

• Fraser and Stanton showed that alcoholic extracts of rice polishings had a curative effect in beriberi.

Biology - 1910

• Sir Henry Hallett Dale studied the properties of histamine.

Biology - 1910

• Paul Ehrlich discovered that solutions of salversan would selectively kill the organism responsible for syphilis.

Biology - 1910

• Epstein and Ottenberg pointed out that the human blood groups (A, B, O) were inherited in accord with Mendelian principles.

Biology - 1910-11

• Schlosser conducted further excavations of Oligocene primate remains from the Fayum.

Biology - 1910-20

• Thomas Hunt Morgan proposed a theory of sex-linked inheritance for the first mutation discovered in Drosophila melanogaster: white eye. This was followed by the announcement of the gene theory, including the principle of linkage.

Biology - 1911

• Casimir Funk isolated crystalline "antineuritis vitamine" (actually B-complex) and coined the word "vitamine" (later changed to vitamin).

Biology - 1911

• E. B. Harvey studied cortical changes in the egg during fertilization.

Biology - 1911

• Hubert Dana Goodale introduced vital staining of the amphibian embryo as a method of tracing the fate of embryonic parts.

Biology - 1911

• Charles Manning Child formulated his axial gradient theory of development.

Biology - 1911

• Richard Benedikt Goldschmidt published the first edition of his Introduction to the Science of Heredity (Einfürung in die Vererbungslehre) in which he summarized his theory of sex determination as a matter of the rate of developmental expression for sex-determining genes. This was based on his study of intersexual forms in moths.

Biology - 1911

• Lucien Claude Cuénot introduced the concept of preadaptation.

Biology - 1911

• Charles Doolittle Walcott discovered a rich assemblage of invertebrate fossils from the middle Cambrian in the Burgess shale of British Columbia.

Biology - 1911

• Sir Ernest Rutherford posited the existence of atomic nuclei.

Biology - 1912

• Alfred Lothar Wegener developed a theory of continental drift based on fossil and glacial evidence, but his theory was ridiculed until long after his death because he could provide no adequate explanation for the cause of the phenomenon.

Biology - 1912

• Carl Neuberg proposed a chemical pathway for fermentation.

Biology - 1912

• F. Batelli and L. S. Stern discovered dehydrogenases.

Biology - 1912

• John Murray and Johan Hjort published The Depths of the Oceans.

Biology - 1912

• Otto Heinrich Warburg postulated a respiratory enzyme for the activation of oxygen, discovered its inhibition by cyanide, and showed the requirement of iron in respiration.

Biology - 1912

• J. F. Gudernatsch found that removal of the thyroid gland would prevent metamorphosis in frogs, and that feeding thyroid extracts could induce precocious metamorphosis.

Biology - 1912

• Edward Albert Sharpey-Schäfer (Schaefer) coined the term "insuline" for the active principle of the pancreas.

Biology - 1912

• G. L. Kite used microsurgical techniques to study the fine structure of cells.

Biology - 1912

• Alexis Carrel developed the technique of in vitro tissue culture. He also developed techniques for transplantation of organs and an artificial heart.

Biology - 1912

• Sir William Henry Bragg and Sir William Lawrence Bragg developed the x-ray crystallography technique which would later be used in the elucidation of the three-dimensional structures of proteins and nucleic acids.

Biology - 1912

• Arthur Smith Woodward announced the discovery of Piltdown man.

Biology - 1912

• Jacques Loeb published The Mechanistic Conception of Life.

Biology - 1912-22

• Heinrich Otto Wieland showed the activation of hydrogen in dehydrogenation reactions.

Biology - 1913

• John Broadus Watson founded the behaviorist school of psychology, which emphasized the study of observable behavior rather than conscious and unconscious mental processes.

Biology - 1913

• Hans Reck discovered rich deposits of early mammalian fossils including Stone Age artifacts at Olduvai Gorge in East Africa.

Biology - 1913

• Leonor Michaelis and Maud L. Menten postulated the existence of an intermediate enzyme-substrate complex to explain the mechanism of enzyme action. (Michaelis is also the father of the home permanent, by virtue of his discovery of the solubility of keratin in thioglycolic acid.)

Biology - 1913

• Calvin Blackman Bridges reported nondisjunction of sex chromosomes as a proof of the chromosome theory of heredity.

Biology - 1913

• Alfred Henry Sturtevant developed the first genetic map by using crossover frequencies as measurements of relative distances.

Biology - 1913

• Thomas Burr Osborne and Lafayette Benedict Mendel showed that rats developed xerophthalmia on diets in which lard supplied the fat; the condition was cured by substitution of butterfat.

Biology - 1913

• Shiro Tashiro measured slight increases in carbon dioxide production in nerves when they were stimulated.

Biology - 1913

• Publication of Richard Willstätter and Arthur Stoll's Unterschungen Über Chlorophyll.

Biology - 1913

• Victor Ernest Shelford formulated the law of ecologic tolerance.

Biology - 1913-1925

• Francis Bertody Sumner studied geographic variation in Peromyscus and convinced himself that the apparently continuous variability was actually Mendelian in nature.

Biology - 1914

• Edward Calvin Kendall completed the final isolation of crystalline thyroxine, the active substance produced by the thyroid gland.

Biology - 1914

• Dr. Joseph Goldberger, of the United States Public Health Service, demonstrates that pellagra, widely held to be a hereditary condition, was actually caused by a diet lacking in meat or milk. The exact cause was later determined to be niacin deficiency.

Biology - 1914

• Frank Rattray Lillie hypothesized the existence of a substance, fertilizin, in the jelly coat of eggs which causes sperm cells to clump together.

Biology - 1914

• Warren Harmon Lewis and his wife, Margaret R. Lewis, described mitochondria.

Biology - 1914

• George Harrison Shull demonstrated the phenomenon of heterosis, commonly referred to as hybrid vigor.

Biology - 1915

• The Mechanism of Mendelian Heredity, an epochal book, published by Thomas Hunt Morgan, Alfred Henry Sturtevant, Calvin Blackman Bridges, and Hermann Joseph Muller.

Biology - 1915

• Frederick Twort discovered a virus capable of infecting and destroying bacteria.

Biology - 1916

• Frank Rattray Lillie demonstrates the role of sex hormones in freemartinism.

Biology - 1916

• Henry Edward Crampton described geographical races of the snail Partula in Tahiti.

Biology - 1917

• Felix Hubert D'Herelle, independently of Frederick Twort, discovered a virus capable of infecting and destroying bacteria, which he called a bacteriophage.

Biology - 1917

• S. Kopec demonstrated the role of the brain in insect metamorphosis.

Biology - 1917

• Ferdinand Broili discovered the fossil remains of Seymouria, an organism showing both amphibian and reptilian characteristics.

Biology - 1917

• Joseph Grinnell introduced the concept of the ecological niche.

Biology - 1917

• Rollins Adams Emerson discovered and analyzed a highly mutable gene in maize. After thirty-five years this gene is still under active study.

Biology - 1917

• Elmer Verner McCollum and Simmonds showed that xerophthalmia in rats is due to lack of a fat-soluble substance which they named vitamin A.

Biology - 1917

• Richard Benedikt Goldschmidt and L. T. Troland suggested that genes were enzymes.

Biology - 1918

• Jacques Loeb introduced the concepts of "forced movements", "tropisms" and "animal conduct". He vehemently opposed any anthropomorphic or teleological interpretations of animal behavior.

Biology - 1918

• Ernest Henry Starling recognized that the greater the volume of blood entering the ventricles of the heart, the greater the force of contraction.

Biology - 1918

• August Krogh showed that capillaries were capable of contracting or dilating due to chemical or nervous controls.

Biology - 1918

• J. S. Szymanski showed that animals were capable of maintaining 24-hour activity patterns in the absence of external cues such as light and temperature. These are now known as "circadian rhythms", or the "biological clock".

Biology - 1918

• Nikolay Ivanovich Vavilov stressed the importance of biologic centers of origin as reservoirs of desirable genes which can be incorporated into cultivated strains derived from those regions.

Biology - 1919

• Sir Jack Cecil Drummond named vitamin C, and proposed the change in spelling from vitamine to vitamin.

Biology - 1919

• Francis William Aston discovered elements occur in different isotopes. Rare isotopes have been used as tracers in the study of biological processes since 1923.

Biology - 1919

• Sir Edward Mellanby produced experimental rickets in puppies.

Biology - 1919

• Wilbur Willis Swingle reproduced Gudernatsch's results on metamorphosis in frogs by providing or withholding inorganic iodine.

Biology - 1919

• Thomas Hunt Morgan and coworkers published The Physical Basis of Heredity, a summary of the rapidly growing findings in genetics.

Biology - 1919

• A. Paál showed that when the tip of a plant shoot is cut off and replaced to one side, the growth of the base is greater on this side.

Biology - 1919

• Otto Warburg found that the efficiency of photosynthesis was increased in intermittent light.

Biology - 1919-20

• Harry Steenbock demonstrated the relationship between vitamin A activity and the plant pigment carotene.

Biology - 1920

• Otto Loewi (Löwi) demonstrated the release of stimulating and inhibitory substance from terminal branches of nerve fibers. This discovery led to the concept of nerve impulse transmission across junctions by means of chemical mediators or neurotransmitters.

Biology - 1920

• R. O. Herzog and W. Jancke contributed to the development of x-ray crystallography.

Biology - 1920

• H. E. Howard investigated the territorial behavior of mating birds.

Biology - 1921

• Hans Spemann described the "organizer" effect of the amphibian dorsal lip region.

Biology - 1921

• Thomas Hunt Morgan estimated the gene to have a diameter of 20-70 microns. Current estimates are considerably lower.

Biology - 1921

• John Newport Langley functionally distinguished and described the autonomic nervous system.

Biology - 1921

• Otto Loewi (Löwi), and, independently, Sir Henry Hallett Dale, isolated the substance released by the vagus nerve. Loewi called the substance "Vagusstoff", but it is now known as acetylcholine.

Biology - 1921

• Alfred Newton Richards collected and analyzed the glomerular filtrate of the kidney. His findings were consistent with the Ludwig-Cushny theory of kidney excretion.

Biology - 1921

• Sir Frederick Gowland Hopkins isolated glutathione from tissue.

Biology - 1921-22

• Sir Frederick Grant Banting, Charles Herbert Best and John James Rickard Macleod isolated insulin and further studied its physiological properties.

Biology - 1922

• Elmer Verner McCollum et al. showed that experimental rickets was caused by lack of a new food factor, vitamin D.

Biology - 1922

• S. Kopec first demonstrated that pupation in an insect is conditioned by an agent in the body fluid that originates in the nervous system. This was the first demonstration of the hormonal activity of the invertebrate nervous system.

Biology - 1922

• Joseph Erlanger and Herbert Spencer Gasser found that the rates of conduction of mammalian nerve fibers corresponded to the thickness of their sheaths.

Biology - 1922

• T. Schjelderup-Ebbe studied social dominance hierarchies (pecking orders) in birds.

Biology - 1922

• Leopold Ruzicka recognized isoprene as the building block of many natural products.

Biology - 1922-23

• Otto Warburg reported first measurements on the quantum efficiency of photosynthesis. Warburg's manometric apparatus became a standard tool for measuring metabolism in living cells.

Biology - 1923

• Johannes Bronsted defined acids as substances which act as proton sources, and bases as substances which act as proton acceptors, regardless of the solvent.

Biology - 1923

• Niels Bjerrum used the strength constants of acids and bases to study the dissociation of other compounds.

Biology - 1923

• George Charles de Hevesy first used an isotopic tracer to study chemical processes in living organisms.

Biology - 1923

• David Keilin rediscovered histohematins (cytochromes) and demonstrated changes in their oxidation state during respiratory activity.

Biology - 1923

• Thorsten Ludvig Thunberg first characterized photosynthesis as an oxidation-reduction reaction in which carbon dioxide was reduced and water was oxidized. He also studied the oxidative degradation of foodstuffs in animals.

Biology - 1924

• L. R. Cleveland studied the mutualistic relationship between termites and their intestinal zooflagellates.

Biology - 1924

• Robert Feulgen developed a chemical test for "thymonucleic acid". This reaction is still widely used to test for DNA.

Biology - 1924

• Stöhr obtained development of an embryonic heart by self-differentiation of trunk mesoderm tissue.

Biology - 1924

• Bernardo Alberto Houssay investigated the role of the pituitary gland in the regulation of carbohydrate metabolism.

Biology - 1925

• Fritz Baltzer discovered that sex determination in some animals is not chromosomal and that juveniles can be sexually ambipotent.

Biology - 1925

• Joseph Barcroft demonstrated the spleen's role as a blood reservoir.

Biology - 1925

• Vogt constructed maps of the prospective fates of parts of the amphibian blastula.

Biology - 1925

• Samuel Ottmar Mast studied the mechanism of amoeboid movement. This study led to the formulation of many useful concepts for understanding other protoplasmic movements, such as cytokinesis. Mast also studied animals' response to light.

Biology - 1925

• Hans Molisch obtained the evolution of oxygen by illuminating preparations of dried leaves.

Biology - 1925

• George Edward Briggs and John Burdon Sanderson Haldane made important refinements in the theory of enzyme kinetics.

Biology - 1925

• Alfred James Lotka published Elements of Physical Biology.

Biology - 1925

• George Richards Minot and William Parry Murphy discovered that feeding raw liver had a pronounced effect in the treatment of pernicious anemia. This discovery led to the eventual isolation of vitamin B12 and the identification of yet another vitamin deficiency disease.

Biology - 1925

• W. Rowan demonstrated the effect of photoperiod on on birds' physiological readiness for mating and migration.

Biology - 1925

• Raymond Arthur Dart discovered the "Taung Baby" fossil, now classified as Australopithecus africanus. The find was especially significant because it included a rough cast of the individual's brain.

Biology - 1925-28

• G. Koller and E. B. Perkins, by means of blood transfusions, obtained evidence of the presence of hormone-like substances regulating the activity of chromatophores in crustaceans.

Biology - 1925-30

• Phoebus Aaron Levene elucidated the structure of mononucleotides and showed they are the building blocks of nucleic acids. He also isolated the carbohydrate portion of nucleic acids and distinguished deoxyribose from ribose.

Biology - 1925-38

• Theodor Svedberg invented the ultracentrifuge and used it to determine the sedimentation rates of proteins.

Biology - 1926

• Otto Loewi (Löwi) and Navratil identified the substance released by the vagus nerve as acetylcholine.

Biology - 1926

• Kenjiró Fujii observed the coiled structure of the chromosome for the first time. In certain stages of the cell cycle, two filaments were seen to be coiled around each other.

Biology - 1926

• Archibald Vivian Hill used a thermocouple to measure the heat produced by stimulated nerve fibers. He also showed that oxygen is consumed in the recovery phase of muscle contraction and is not directly required for contraction.

Biology - 1926

• James Batcheller Sumner first crystallized an enzyme, urease, and proved it to be a protein.

Biology - 1926

• B. C. P. Jansen and Donath isolated crystalline thiamin--vitamin B1--from rice polishings.

Biology - 1926-28

• Frits Warmolt Went demonstrated that the material responsible for phototropism (later called auxins) in plants could diffuse into agar blocks and thus be collected. He developed quantitative assay methods for the growth substance.

Biology - 1927

• Emil Bozler demonstrated that the nerve net of cnidarians was made up of separate cells connected by synaptic junctions. He also studied electrical aspects of muscle contraction and the role of calcium and magnesium in contraction and relaxation.

Biology - 1927

• George Ellett Coghill investigated the innate behavior patterns of salamanders.

Biology - 1927

• Adolf Otto Reinhold Windaus and others identified ergosterol as the parent substance of vitamin D.

Biology - 1927

• Sir Charles Robert Harington synthesized thyroxine.

Biology - 1927

• Erik Anderson Stensiö reconstructed a fossil Cephalapsid (an ostracoderm) and suggested its status as a vertebrate prototype.

Biology - 1927

• Karpchenko obtained a tetraploid hybrid between the cabbage and the radish, thus creating the new species Raphanobrassica.

Biology - 1927

• Artificial transmutation of the gene was reported by L. J. Stadler in plants and Hermann Joseph Muller in Drosophila by means of x-rays.

Biology - 1927

• Karl Landsteiner discovered the M and N blood groups.

Biology - 1927

• Theophilus Shickel Painter found a chromosome deficiency in mice which, along with genetic evidence, provided the first case of localizing a specific gene to a particular chromosome in mammals.

Biology - 1927-28

• P. Eggleton, G. P. Eggleton, Cyrus Hartwell Fiske and Y. Subbarow discovered phosphagen in muscle and investigated its role in contraction.

Biology - 1927-29

• Corneille Heymans investigated the role of the carotid and aortic reflexes in respiratory control.

Biology - 1928

• W. Garstang theorized that chordates evolved from organisms resembling ascidians.

Biology - 1928

• Volhard suggested that a substance in the kidney may be responsible for some cases of hypertension.

Biology - 1928

• Fredrick Griffith discovered a "transforming principle" in pneumococci that was capable of transforming nonvirulent strains into virulent strains.

Biology - 1928

• H. von Euler-Chelpin prepared pure carotene and demonstrated its high vitamin A activity.

Biology - 1928

• Albert von Szent-Györgyi showed that hexuronic acid was identical with vitamin C and proposed the name ascorbic acid.

Biology - 1928

• Sir Alexander Fleming discovered the antibacterial action of penicillin.

Biology - 1928

• Heinrich Otto Wieland and Adolf Otto Reinhold Windaus elucidated the structure of the cholesterol molecule.

Biology - 1928-33

• Otto Warburg deduced the iron-porphyrin nature of the respiratory enzyme.

Biology - 1929

• K. Lohmann, Cyrus Hartwell Fiske and Y. Subbarow isolated ATP and phosphocreatinine from muscle extracts.

Biology - 1929

• Hans Berger devised equipment to make the first encephalograms (measurements of brain waves) of human subjects.

Biology - 1929

• Adolf Friedrich Johann Butenandt and Edward Adelbert Doisy isolated the first sex hormone, estrone, from urine.

Biology - 1929

• William Bosworth Castle showed that the substance responsible for preventing pernicious anemia arose from the combination of an intrinsic factor in the gastric juice and an extrinsic factor in the diet. This antianemic factor was then stored in the liver.

Biology - 1930

• E. Lundsgaard proved that muscles could contract without lactic acid formation.

Biology - 1930

• Cornelis Van Niel suggested the parallelism between photosynthetic processes in bacteria and green plants.

Biology - 1930

• L. J. Stadler devised and perfected methods for determining spontaneous mutations rates in maize, finding that different genes mutate at widely different rates.

Biology - 1930

• Sewall Wright's studies on the mathematics of evolutionary changes in populations were published.

Biology - 1930

• Publication of Ronald Aylmer Fisher's The Genetical Theory of Natural Selection.

Biology - 1930-33

• John Howard Northrop crystallized pepsin and trypsin and proved their protein nature.

Biology - 1930-35

• John Tileston Edsall and A. von Muralt isolated myosin from muscle.

Biology - 1931

• V. A. Engelhardt discovered that phosphorylation of ATP is coupled to respiration.

Biology - 1931

• Warren Harmon Lewis characterized the process of pinocytosis.

Biology - 1931

• H. B. Creighton and Barbara McClintock demonstrated a cytological proof for crossing over in maize. A similar demonstration was made by Curt Stern in Drosophila.

Biology - 1931

• Sewall Wright presented the first unified picture of evolution in terms of Mendelism illustrating the relations between selection pressure, mutation rates. inbreeding, isolation and the like.

Biology - 1931

• On the basis of radioactivity and geological data, the age of the earth was shown to be at least two billion years.

Biology - 1932

• K. Lohmann discovered the ATP-phosphocreatinine reaction.

Biology - 1932

• Otto Warburg and W. Christian isolated a yellow conjugated flavoprotein from yeast: the yellow enzyme of respiration.

Biology - 1932

• Theodosius Dobzhansky, Theophilus Shickel Painter, and Hermann Joseph Muller showed that while the seriation of genes is the same for genetic and cytological maps, physical distances and crossover map distances did not coincide.

Biology - 1932

• Sewall Wright stressed the importance of "genetic drift" due to chance in small populations.

Biology - 1932

• Richard Benedikt Goldschmidt studied adaptation in geographical races of the Gypsy moth.

Biology - 1932

• A. Bethe introduces the concept of ectohormones, now known as pheromones.

Biology - 1932

• A Danish scientific expedition found ichthyostegid fossils in Greenland. These are the oldest known fossils that can be classified as amphibians.

Biology - 1932

• Edward G. Lewis found the first Ramapithecus, the earliest known hominid fossil.

Biology - 1932

• M. Kroll and Ernst August Friedrich Ruska built the first electron microscope.

Biology - 1933

• N. W. Timofeeff-Ressovsky experimentally measured the viability of strains of Drosophila funebris of different geographical origin.

Biology - 1933

• F. Kögl, Haagen-Smit, and Erxleben isolated auxins and characterized them chemically.

Biology - 1933

• Sir Hans Adolf Krebs and K. Henseleit discovered the urea cycle.

Biology - 1933

• R. Collander and H. Bärlund made quantitative measurements of cell membrane permeability to nonelectrolytes of varying molecular size and lipid solubility. Their results contributed enormously to our understanding of membrane structure.

Biology - 1933

• Gustav Embden and Otto Meyerhof each demonstrated crucial intermediates in the chemical pathway of glycolysis and fermentation.

Biology - 1933

• David Keilin isolated cytochrome C and reconstituted electron transport in particulate heart preparations.

Biology - 1933

• George Wald discovered vitamin A in the retina.

Biology - 1933

• M. Goldblatt and Ulf Svante von Euler discovered prostaglandins.

Biology - 1933

• Johannes Friedrich Karl Holtfreter produced exogastrulae, an important tool for understanding embryonic induction.

Biology - 1933

• John Burdon Sanderson Haldane and Aleksandr Ivanovich Oparin advanced a heterotroph theory of the origin of life

Biology - 1933-34

• Theophilus Shickel Painter, Emile Heitz and H. Bauer recognized the value of Drosophila's giant salivary chromosomes in genetic analysis. This facilitated extensive studies on precise gene localization and chromosome structure.

Biology - 1933-35

• Hans Spemann, Joseph Needham, and others showed that cell-free extracts from the organizer region retained powers of evocation. Chemical studies of Needham, Conrad Hal Waddington, and others led to the belief that the evocator was probably a sterol.

Biology - 1934

• L'Héritier and Teissier devised the "population cage" method for the experimental study of natural selection.

Biology - 1934

• Robert Russell Bensley and N. L. Hoerr isolated and analyzed mitochondria.

Biology - 1934

• Henrik Dam and Edward Adelbert Doisy isolated and identified vitamin K.

Biology - 1935

• A. G. Tansley formulates the concept of the ecosystem.

Biology - 1935

• Francis Bertody Sumner experimentally showed the selective value of protective coloration in fishes.

Biology - 1935

• Sven Otto Hörstadius showed the existence of a double gradient of "animalization" and "vegetalization" in the echinoderm egg.

Biology - 1935

• Zimmerman and Wilcoxon discovered several synthetic substances with hormone activity in plants.

Biology - 1935

• Wendell Meredith Stanley first crystallized a virus: tobacco mosaic virus.

Biology - 1935

• Paul Karrer and Richard Kuhn identified lactoflavin (riboflavin, or vitamin B2) as the prosthetic group of Otto Warburg and W. Christian's yellow enzyme.

Biology - 1935

• Albert von Szent-Györgyi showed the catalytic effect of dicarboxylic acids on respiration.

Biology - 1935

• Robert R. Williams and his colleagues deduced the structure of vitamin B1.

Biology - 1935

• George Wald suggested that vitamin A is a precursor of visual purple.

Biology - 1935

• William Cumming Rose discovered threonine, the last essential amino acid to have been recognized.

Biology - 1935

• Rudolf Schoenheimer and David Rittenberg first used isotopes as tracers in the study of intermediate metabolism of carbohydrates and lipids.

Biology - 1935

• H. Davson and James Frederic Danielli proposed a "protein-lipid sandwich" model for the structure of cell membranes.

Biology - 1935

• N. W. Timofeeff-Ressovsky formulated a "target theory" of gene mutation which says that a mutation can be induced if a single electron is detached by high energy radiation.

Biology - 1935-36

• Edward Calvin Kendall and Phillip Showalter Hench discovered cortisone.

Biology - 1935-36

• L. S. Stern spectroscopically demonstrated the existence of an intermediate enzyme-substrate complex for the enzyme catalase, thus confirming the Michaelis-Menten hypothesis.

Biology - 1935-36

• Otto Warburg and Hans von Euler-Chelpin isolated pyrimidine nucleotides and determined their structure and action.

Biology - 1936

• Harland Goff Wood and C. Werkman discovered that plant cells kept in the dark are able to build up larger organic molecules from carbon dioxide.

Biology - 1936

• J. Z. Young discovered giant nerve fibers in squid.

Biology - 1936

• Wendell Meredith Stanley isolated nucleic acid from tobacco mosaic virus.

Biology - 1936

• Robert R. Williams and Kline synthesized thiamin.

Biology - 1936

• Millislav Demerec and M. E. Hoover pointed out the correspondence between giant salivary gland chromosome bands and gene maps.

Biology - 1936

• Publication of Theodosius Dobzhansky's Genetics and the Origin of Species.

Biology - 1937

• K. Lohmann and P. Schuster isolated the prosthetic group from cocarboxylase and showed that it is the diphosphate of thiamin (vitamin B1).

Biology - 1937

• Sir Hans Adolf Krebs Krebs and W. A. Johnston postulated the citric acid cycle.

Biology - 1937

• Eugen Werle, W. Gotze and A. Keppler discovered kinins.

Biology - 1937

• Avery, Burkholder and others pursued quantitative studies on effects of auxins in plant metabolism.

Biology - 1937

• Kenneth Vivian Thimann suggested that a given concentration of auxin might produce inhibitory effects in one tissue and stimulation in another, different tissues being characterized by a series of overlapping optimal concentration curves.

Biology - 1937

• Albert Francis Blakeslee and Avery used colchicine to produce artificial polyploidy in plant cells.

Biology - 1937

• P. König and Arne Tiselius developed the technique of electrophoresis.

Biology - 1937

• George William Marshall Findlay and F. O. MacCullum discovered interferon.

Biology - 1937

• Tracy Morton Sonneborn recognized the existence of different mating types in Paramecium.

Biology - 1937

• Sir Frederick Charles Bawden discovered that the tobacco mosaic virus contains RNA.

Biology - 1937

• Carl Ferdinand Cori and Gerty Theresa Cori began their incisive studies of glycogen phosphorylase.

Biology - 1937-38

• Otto Warburg showed how formation of ATP is coupled to the dehydrogenation of glyceraldehyde 3-phosphate.

Biology - 1937-41

• Herman Moritz Kalckar and Vladimir Aleksandrovitch Belitser independently carried out the first quantitative studies of oxidative phosphorylation.

Biology - 1938

• Van Overbeek reported that certain nongeotropic mutants in maize did not show the usual inequality of auxin distribution.

Biology - 1938

• Burrhus Frederick Skinner invented the Skinner box, and used it to investigate operant conditioning in rats.

Biology - 1938

• Jean Louis Brachet showed that ribonucleic acids are accumulated in regions of high morphogenetic activity.

Biology - 1938

• Robin Hill found that cell-free suspensions of chloroplasts evolve oxygen when illuminated in the presence of ferric salts.

Biology - 1938

• A. Braunstein and Kritzman discovered transamination reactions.

Biology - 1938

• William Thomas Astbury and F.O. Bell first used X-ray crystallography to analyze the structure of DNA.

Biology - 1938

• Rudolf Schoenheimer applied radioactive tracers to the study of the biosynthesis of cell structures and concluded that the body is in a state of dynamic equilibrium.

Biology - 1939

• Latimeria, a living crossopterygian fish, was caught off the coast of South Africa. The order Crossopterygii was believed to have died out in the Cretaceous period after it gave rise to the amphibian line.

Biology - 1939

• Carl Ferdinand Cori and Gerty Theresa Cori demonstrated the reversible action of glycogen phosphorylase.

Biology - 1939

• Gregory Goodwin Pincus was able to induce parthenogenesis in a mammalian egg.

Biology - 1939

• Sven Otto Hörstadius differentiated eggs into the categories "regulative" and "mosaic" depending on their pattern of development.

Biology - 1939

• Publication of Ernest Everett Just's The Biology of the Cell Surface.

Biology - 1939

• Julian Huxley introduces the concept of the cline in evolutionary variation.

Biology - 1939

• Ruben, William Zev Hassid and Martin David Kamen first applied radioactive tracers to the study of photosynthesis.

Biology - 1939

• Borgström found that shoots exposed to ethylene exhibited positive geotropism associated with the predicted auxin distribution. Ethylene must in some way influence the transverse movement of auxin.

Biology - 1939

• Russel E. Marker developed a method for synthesizing progesterone in large quantities.

Biology - 1939-41

• Fritz Albert Lipmann postulated the central role of ATP in the energy transfer cycle.

Biology - 1939-42

• V.A. Engelhardt and M. N. Lyubimova discovered the ATPase activity of myosin.

Biology - 1939-46

• Albert von Szent-Györgyi discovered actin and actomyosin and explicated the role of ATP in muscle contraction..

Biology - 1940-41

• George Wells Beadle and Edward Lawrie Tatum deduced the one gene-one enzyme relationship from their work on Neurospora crassa. Their work profoundly advanced our understanding of the biochemical effects of mutations.

Biology - 1940

• Karl Landsteiner and Alexander Solomon Wiener discovered the Rh blood factor.

Biology - 1940

• Gaffron showed that algae can utilize molecular hydrogen for photosynthesis.

Biology - 1940

• Kausche and Ernst August Friedrich Ruska published first electron microscope pictures of chloroplasts.

Biology - 1940-43

• A. Claude isolated a mitochondrial fraction from liver by differential centrifugation.

Biology - 1941

• Ruben, Randall, Martin David Kamen, and Hyde reported that the oxygen liberated in photosynthesis comes from water.

Biology - 1941

• Barry Commoner and Kenneth Vivian Thimann found that concentrations of 10-5 M of iodoacetate can halt coleoptile growth but produce no effect on cellular respiration. They assumed that only a small fraction of respiration might be involved in growth.

Biology - 1941

• Carl Ferdinand Cori and Gerty Theresa Cori worked out the lactic acid metabolic cycle.

Biology - 1941

• Selman Abraham Waksman coined the term "antibiotic" to describe compounds produced by microorganisms which kill bacteria.

Biology - 1941

• Publication of Charles Manning Child's Patterns and Problems of Development, an analysis of development from the viewpoint of the gradient concept.

Biology - 1941

• Gustaffson and coworkers produced agriculturally superior new strains of cereals by selection from mutants produced by x-rays.

Biology - 1941-44

• Archer John Porter Martin and Richard Laurence Millington Synge developed partition chromatography and applied it to amino acid analysis.

Biology - 1942

• D. McClean and I. M. Rowlands discovered hyaluronidase in mammalian sperm.

Biology - 1942

• Konrad Emil Bloch and David Rittenberg discovered that acetate is the precursor of cholesterol.

Biology - 1942

• Salvador Edward Luria obtained the first high-quality electron micrograph of a bacteriophage.

Biology - 1942

• Reinders found that auxin present in concentrations as low as 1mg/liter stimulated water uptake in potato discs along with an increase in respiration and loss in dry weight.

Biology - 1943

• David Ezra Green and Carl Ferdinand Cori crystallized muscle phosphorylase.

Biology - 1943

• Barry Commoner, Fogel and Detlev Muller demonstrated that auxin will promote water absorption against an osmotic gradient. The effect is inhibited by iodoacetate.

Biology - 1943

• Britton Chance spectroscopically demonstrated the existence of an enzyme-substrate complex for catalase.

Biology - 1943

• Severo Ochoa demonstrated the 3:1 phosphorus to oxygen ratio of oxidative phosphorylation in the citric acid cycle.

Biology - 1943

• Johannes Friedrich Karl Holtfreter demonstrated that dissociated cells from the same tissue would resynthesize that tissue if they were kept in contact with each other.

Biology - 1943

• Joachim Hämmerling demonstrated by a series of transplantation experiments that the cap morphology of two related species of the unicellular alga Acetabularia depends on the species of the nucleus.

Biology - 1943

• Tracy Morton Sonneborn demonstrated extranuclear inheritance in Paramecium.

Biology - 1943-47

• L. F. Leloir and J. M. Munoz demonstrated fatty acid oxidation in cell-free liver systems; Albert Lester Lehninger showed the requirement of ATP and the stoichiometry of fatty acid oxidation.

Biology - 1944

• Oswald Avery, Colin MacLeod and Maclyn McCarty demonstrated that bacterial transformation is caused by DNA. Some considered this a demonstration that DNA, not protein, was the hereditary material, but most were not convinced, owing partly to the cautious tone of the publication.

Biology - 1945

• Carl Ferdinand Cori demonstrated the effect of insulin on hexokinase. This was the first demonstration of such a regulatory effect.

Biology - 1945

• Keith Roberts Porter described the structure of the endoplasmic reticulum.

Biology - 1945

• Brand reported the first complete amino acid analysis of a protein, beta-lactoglobulin, by chemical and microbiological methods.

Biology - 1946

• C. Auerbach and J. M. Robson demonstrate chemical mutagenesis.

Biology - 1946

• Joshua Lederberg and Edward Lawrie Tatum studied the process of conjugation in Escherichia coli.

Biology - 1946

• Willard Frank Libby developed the carbon-14 dating technique.

Biology - 1946

• E. I. White discovered a fossil of Jamoytius, probably the most primitive known chordate.

Biology - 1947

• Peter Wilhelm Joseph Holtz discovered the hormone noradrenalin (norepinephrine).

Biology - 1947

• R. C. Sprigg discovered a rich deposit of Precambrian fossils in the Ediacara Hills of South Australia.

Biology - 1947

• Albert von Szent-Györgyi found that neither actin or myosin was independently capable of contraction. He coined the term "actomyosin" to describe the protein complex responsible for muscle contraction.

Biology - 1947-50

• Fritz Albert Lipmann and Kaplan isolated and chemically characterized coenzyme A.

Biology - 1948

• L. F. Leloir and his colleagues discovered the role of uridine nucleotides in carbohydrate metabolism.

Biology - 1948

• Karl von Frisch studied communication in honeybees.

Biology - 1948

• Walter Rudolf Hess perfected a method of implanting electrodes in the brains of rats and was able to localize centers of the brain associated with certain instincts.

Biology - 1948

• G. H. Hogeboom, Walter Carl Schneider, and George Emil Palade refined the differential centrifugation method for cell fractionation and used it to isolate mitochondria.

Biology - 1948

• Benjamin Minge Duggar discovered aureomicin, the first tetracycline antibiotic.

Biology - 1948

• Melvin Calvin and Benson reported that the major intermediate compound in which carbon is fixed in photosynthesis is phosphoglyceric acid.

Biology - 1948-50

• Eugene Patrick Kennedy and Albert Lester Lehninger discovered that the citric acid cycle, fatty acid oxidation, and oxidative phosphorylation take place in mitochondria.

Biology - 1949

• Christian René de Duve discovered the lysosome.

Biology - 1949

• William Howard Stein and Stanford Moore reported the complete amino acid analysis of beta-lactoglobulin, determined by starch column partition chromatography.

Biology - 1949

• John Franklin Enders and Frederick Chapman Robbins and Thomas Huckle Weller found that animal viruses could be grown in cell culture instead of live animals.

Biology - 1949

• Ulf Svante von Euler studied the role of norepinephrine as a sympathetic neurotransmitter.

Biology - 1949

• Linus Carl Pauling showed that sickle cell hemoglobin showed different electrophoretic properties than normal hemoglobin. This demonstrated that genetic mutations lead to specific chemical changes in protein molecules.

Biology - 1949

• Hans Selye developed the concept of the stress syndrome after a twelve year study of the physiological effects of stress on animals.

Biology - 1949-50

• Frederick Sanger developed the 2,4-dinitrofluorobenzine method and Edman developed the phenylisothiocyanate procedure for identification of the N-terminal residues of peptides.

Biology - 1950

• H. G. Callan and S. G. Tomlin described the structure of the nuclear membrane as a double membrane with pores.

Biology - 1950

• Tobjörn Oskar Caspersson and Jean Louis Brachet studied the role of RNA in protein synthesis.

Biology - 1950

• Linus Carl Pauling and R. B. Corey proposed the alpha-helix structure for alpha-keratin.

Biology - 1950

• M. Simpson and Choh Hao Li point out that hormonal coordination is necessary for the balanced development of tissue.

Biology - 1950

• Konrad Lorenz establishes the discipline of ethology.

Biology - 1950-53

• Erwin Chargaff and coworkers discovered base equivalencies in DNA: the amount of purines always equals the amount of pyrimidines, the amount of adenine always equals the amount of thymine and the amount of guanine always equals the amount of cytosine.

Biology - 1951

• Edward B. Lewis introduced the notion of pseudoallelism.

Biology - 1951

• Carl Djerassi, following the methods of Russel E. Marker, synthesized 19-Norsteroids, a powerful synthetic progesterone.

Biology - 1951

• John Rock, Gregory Goodwin Pincus and Min Chuch Chang discover that 19-Norsteroids prevents ovulation in women.

Biology - 1951

• Albert Lester Lehninger showed that electron transport from NADH to oxygen is the immediate energy source for oxidative phosphorylation.

Biology - 1951

• Feodor Lynen postulated the role of coenzyme A in fatty acid oxidation.

Biology - 1951

• The laboratories of Feodor Lynen, David Ezra Green, and Severo Ochoa isolated the enzymes of fatty acid oxidation.

Biology - 1952

• Alfred Day Hershey and Martha Chase proved, on the basis of their bacteriophage research, that DNA alone carries genetic information.

Biology - 1952

• Norton David Zinder and Joshua Lederberg discovered transduction: bacterial DNA can be carried from one bacterium to another by a bacteriophage virus.

Biology - 1952

• W. Beerman associated chromosomal puffs with gene activation.

Biology - 1952

• Jean Louis Brachet suggested that movements of microsomes (which contain ribonucleic acid) from the archenteron roof to the overlying ectoderm are involved in neural induction.

Biology - 1952

• Robert William Briggs and T. J. King demonstrated an apparent developmental differentiation in nuclear genotypes.

Biology - 1952

• Gustav Kramer demonstrates sun-compass orientation in birds.

Biology - 1952-53

• George Emil Palade, Keith Roberts Porter, and Fritiof Stig Sjöstrand perfected thin sectioning and fixation methods for electron microscopy of intracellular structures, especially of mitochondria.

Biology - 1952-53

• Rosalind Franklin produced precise X-ray diffraction images of the B form of DNA.

Biology - 1952-54

• Paul Charles Zamecnik and his colleagues discovered that ribonucleoprotein particles, later named ribosomes, are the site of protein synthesis.

Biology - 1953

• George Emil Palade described ribosomes.

Biology - 1953

• James Dewey Watson and Francis Harry Compton Crick accurately described the molecular structure of DNA.

Biology - 1953

• Frederick Sanger, E. O. P. Thompson and Hans Tuppy completed the determination of the amino acid sequence of the A and B chains of insulin.

Biology - 1953

• Bernard Leonard Horecker, Dickens, and Efraim Racker elucidated the 6-phosphogluconate pathway of glucose catabolism.

Biology - 1953

• André Michael Lwoff found that bacteriophage viruses were capable of inserting their genome into the host genome. A virus in this condition is known as a prophage.

Biology - 1953

• Harold Clayton Urey and Stanley Lloyd Miller found that several amino acids were formed when ammonia, methane, water vapor and hydrogen were exposed to an electrical discharge for several days. This suggested a possible scenario for the origin of life on the primitive earth.

Biology - 1953-54

• Vincent du Vigneaud carried out the first laboratory synthesis of the peptide hormones oxytocin and vasopressin.

Biology - 1954

• Bernard Katz described impulse transmission across a synapse.

Biology - 1954

• Hugh Esmore Huxley, Jean Hanson R. Niedergerde, and Andrew Fielding Huxley formulated the sliding filament theory of muscle contraction.

Biology - 1954

• Daniel I. Arnon and colleagues discovered photosynthetic phosphorylation.

Biology - 1954

• Britton Chance and G. R. Williams applied the oxygen electrode and difference spectrophotometry to the study of the dynamics of electron transport in mitochondria.

Biology - 1954

• Revised estimates put the age of the earth at five to six billion years.

Biology - 1954

• J. C. Dan described the acrosome reaction in sperm.

Biology - 1954-58

• E. P. Kennedy described the pathway of biosynthesis of triacylglycerols and phosphoglycerides and the role of cytidine nucleotides.

Biology - 1955

• Frederick Sanger and his colleagues reported the position of the disulfide cross-linkages between the A and B chains of insulin.

Biology - 1955

• Seymour Benzer carried out fine-structure genetic mapping and concluded that a gene has many mutable sites.

Biology - 1955

• Severo Ochoa and M. Grunberg-Manago discovered polynucleotide phosphorylase and successfully synthesized RNA.

Biology - 1955

• Heinz Fraenkel-Conrat and Robley Cook Williams separated TMV nucleic acid from its protein coat and found that both were necessary for infection.

Biology - 1955

• H. D. B. Kettlewell demonstrated the effects of natural selection on melanic and mottled forms of Biston betularia in two different environments.

Biology - 1956

• Arthur Kornberg discovered DNA polymerase.

Biology - 1956

• H. Borsook and Paul Charles Zamecnik found the ribosomes of the endoplasmic reticulum to be the site of protein synthesis.

Biology - 1956

• H. E. Umbarger reported that the end product isoleucine inhibits the first enzyme in its biosynthesis from threonine. Yates and Pardee reported the feedback inhibition of aspartate transcarbamoylase by cytidine triphosphate.

Biology - 1956

• Christian Boehmer Anfinsen and White concluded that the three-dimensional conformation of proteins is specified by their amino acid sequence.

Biology - 1956

• William Stanley Peart and D. F. Eliot isolated angiotensin.

Biology - 1956

• E. W. Sutherland and T. W. Rall discovered cyclic AMP.

Biology - 1956

• Joe-Hin Tjio and Johan Albert Levan revised Walther Flemming's 1898 estimate of the human chromosome count from 24 pairs to 23 pairs.

Biology - 1956

• George von Békésy's traveling wave theory of hearing replaces the resonance theory.

Biology - 1956-58

• Vernon Martin Ingram showed that normal and sickle-cell hemoglobin differ in a single amino acid residue in one of the chains.

Biology - 1957

• Vogel, Magasanik, and others described genetic repression of enzyme synthesis.

Biology - 1957

• Seymour Benzer introduced the concept of the cistron: the smallest unit of function of the gene.

Biology - 1957

• E. W. Sutherland discovered cyclic adenylic acid.

Biology - 1957

• Mahlon Bush Hoagland, Paul Charles Zamecnik, and M.L Stephenson isolated transfer RNA and postulated its function.

Biology - 1957

• J. C. Skou discovered Na+ K+-stimulated ATPase and postulated its role in the transport of Na+ and K+ across the cell membrane.

Biology - 1957

• John Cowdery Kendrew elucidated the three-dimensional structure of myoglobin.

Biology - 1957

• Melvin Calvin and his coworkers completed a step by step analysis of the reactions involved in the synthesis of carbohydrates in plants.

Biology - 1957

• F. Sauer used a planetarium to study stellar navigation in birds.

Biology - 1957

• R. W. Holley explicated the role of transfer RNA in protein synthesis.

Biology - 1957

• James Herbert Taylor, Philip Sargent Woods, and W. L. Hughes demonstrated semiconservative replication in DNA using 3H and autoradiography.

Biology - 1958

• Matthew Messelson and Franklin Stahl demonstrated semiconservative replication in DNA using 15N and ultracentrifugation in a density gradient.

Biology - 1958

• Francis Harry Compton Crick enunciated the central dogma of molecular genetics: information flows from DNA to RNA to protein.

Biology - 1958

• William Howard Stein, Stanford Moore, and Spackman devised the automatic amino acid analyzer, which greatly accelerated the analysis of proteins.

Biology - 1958-59

• Samuel Bernard Weiss, J. Hurwitz and others discovered the DNA-directed RNA polymerase.

Biology - 1959

• Sir Frank Mcfarlane Burnet formulated the clonal selection theory of immunity.

Biology - 1959

• C. E. Ford, P. E. Jacobs and Joe-Hin Tjio elucidated the chromosomal basis of sex determination in humans.

Biology - 1959

• Jerome Jean Louis Marie LeJeune, M. Gautier and Raymond Alexandre Turpin discovered an extra chromosome in the nuclei of cells obtained from children with Down's syndrome.

Biology - 1959

• Max Perutz elucidated the three-dimensional structure of hemoglobin.

Biology - 1959

• Mary Leaky discovered the Zinjanthropus boisei fossil, now considered to be an ultrarobust ausralopithecine.

Biology - 1959

• Adolf Friedrich Johann Butenandt isolated and chemically analyzed for the first time a pheromone: bombykol, the sex attractant of the silk moth.

Biology - 1959-60

• R. Yalow and Solomon Aaron Berson developed the radioimmunoassay.

Biology - 1960

• John Cowdery Kendrew reported the high-resolution x-ray analysis of the three-dimensional structure of sperm whale myoglobin.

Biology - 1960

• François Jacob and Jacques Lucien Monod proposed the operon hypothesis for the regulation of enzyme synthesis.

Biology - 1960

• Hirs, Stanford Moore, and William Howard Stein determined the amino acid sequence of ribonuclease; Christian Boehmer Anfinsen made important independent contributions.

Biology - 1960

• Robert Burns Woodward synthesized chlorophyll a.

Biology - 1960-68

• Elwyn LaVerne Simons conducted the most extensive excavations ever undertaken on the Oligocine formation of the Fayum, contributing enormously to our knowledge of the early development of the higher primates.

Biology - 1961

• François Jacob, Jacques Lucien Monod, and Jean-Pierre Changeux proposed a theory of the function and action of allosteric enzymes.

Biology - 1961

• Jacques Francis Albert Pierre Miller elucidated the role of the thymus gland in the development of immunity.

Biology - 1961

• François Jacob and Jacques Lucien Monod postulated the function of messenger RNA.

Biology - 1961

• Peter Mitchell postulated the chemiosmotic hypothesis for the mechanism of oxidative and photosynthetic phosphorylation.

Biology - 1961

• Marshall Warren Nirenberg and J. Heinrich Matthaei reported that polyuridylic acid codes for polyphenylalanine and thus opened the way to identification of the genetic code.

Biology - 1961

• Robert Palese Perry found that messenger and transfer RNA are synthesized on the chromosomes, and ribosomal RNA is synthesized in the nucleolus.

Biology - 1961-65

• The laboratories of Robert William Holley, Marshall Warren Nirenberg, Har Gobind Khorana and Severo Ochoa identified the genetic code words for the amino acids.

Biology - 1961-68

• Efraim Racker and his colleagues isolated F1 ATPase from mitochondria and subsequently reconstituted oxidative phosphorylation in submitochondrial vesicles.

Biology - 1962

• Douglas Harold Copp discovered calcitonin.

Biology - 1963

• William Donald Hamilton proposed a process of kin selection to explain the selective advantage of neuter castes in the social insects.

Biology - 1964

• Bill Henriksen Hoyer, Brian John McCarthy and Ellis Truesdale Bolton pointed out that similarities in polynucleotide sequences in different species's DNA could be used as a measurement of phylogenetic proximity.

Biology - 1965

• Genes conveying resistance to antibiotics in bacteria were found to reside on small, supernumerary chromosomes called plasmids.

Biology - 1966

• The Endangered Species Act is created.

Biology - 1967

• Mark Ptashne isolated the first repressor protein.

Biology - 1967

• Bernard Weiss and Charles Clifton Richardson isolated and studied a polynucleotide (DNA) ligase from E. coli.

Biology - 1967

• W.M. Fitch and E. Margoliash calculated the phylogenetic relationships of twenty organisms, ranging from fungi to mammals, by comparing their cytochrome C amino acid sequences.

Biology - 1967

• Robert H. MacArthur and Edward Osborne Wilson establish the discipline of theoretical ecology.

Biology - 1968

• Jane van Lawick-Goodall studied the social behavior of free-living chimpanzees.

Biology - 1970

• Gerald M. Edelman and R.R. Porter elucidated the structure of gamma globulin.

Biology - 1970

• Howard Martin Temin and David Baltimore independently discovered retroviruses: RNA viruses capable of reverse transcription: synthesizing DNA from an RNA template.

Biology - 1970

• The first restriction enzyme was isolated.

Biology - 1971

• Lynn Margulis proposed an endosymbiont theory for the origins of eucaryotic organelles.

Biology - 1972

• Robert Burns Woodward and Albert Eschenmoser synthesized vitamin B12.

Biology - 1972

• Seymour Jonathan Singer and Garth L. Nicolson proposed a fluid-mosaic model for the structure of cell membranes.

Biology - 1972

• Workers at Stanford University construct the first recombinant DNA molecules using restriction enzymes and DNA ligase.

Biology - 1973

• Stanley Norman Cohen and Herbert Wayne Boyer demonstrated that restriction enzymes could be used to transfer genes from one species to another. Recombinant DNA plasmids were successfully implanted in Escherischia coli cells, thus demonstrating the possibility of cloning foreign genes in bacterial cells.

Biology - 1973

• The Endangered Species Act was extended and strengthened.

Biology - 1973

• Public concern arose over the possibility of the production of potentially dangerous microorganisms by recombinant DNA technology.

Biology - 1974

• Critics of recombinant DNA technology called for a worldwide moratorium on certain classes of recombinant DNA experiments.

Biology - 1975

• A government report in the United Kingdom called for special laboratory precautions to be employed in recombinant DNA research.

Biology - 1975

• An international conference was convened in Asilomar, California which urged strict guidelines regulating recombinant DNA research.

Biology - 1975

• Edward Osborne Wilson's Sociobiology published.

Biology - 1975

• Joseph William Sanger found that actin and myosin were responsible for the movement of chromosomes on their spindle fibers.

Biology - 1976

• Albert Schmitz, Ursula Schmeissner, Jeffrey H. Miller and Ponzy Lu altered the amino acid composition of the lac repressor protein to determine which amino acids are necessary for the various functions of the complete protein.

Biology - 1976

• The National Institutes of Health published their first guidelines restricting many categories of recombinant DNA experimentation.

Biology - 1977

• Genentech, the first genetic engineering company, is founded to use recombinant DNA methods to produce medically important drugs.

Biology - 1977

• The first recombinant DNA molecules incorporating mammalian DNA were produced. Split genes were discovered.

Biology - 1977

• Procedures were developed for rapidly sequencing long sections of DNA.

Biology - 1977

• Smallpox was eradicated worldwide.

Biology - 1978

• The Nobel Prize in Medicine was awarded for the discovery and use of restriction enzymes.

Biology - 1978

• Somatostatin was produced using recombinant DNA methods.

Biology - 1979

• The NIH guidelines were relaxed, permitting the study of viral DNAs using recombinant DNA procedures.

Biology - 1979

• DNA from malignant cells was used to transform cultured mouse cells, permitting cancer genes to be studied in cell culture.

Biology - 1980

• Construction was begun on the first industrial plant designed to make insulin using recombinant DNA methods.

Biology - 1980

• The Nobel Prize in Chemistry was awarded for the creation of the first recombinant DNA molecules and the development of powerful DNA sequencing methods.

Biology - 1981

• Genentech offers stock in the company for sale to the general public. Valuation by Wall Street was in excess of $200 million.

Biology - 1981

• Gene cloning experiments using laboratory strains of Escherischia coli and yeast as hosts for propagation of recombinant DNA were exempted from the NIH guidelines.

Biology - 1981

• Sickle cell anemia became the first genetic illness to be diagnosed antenatally directly at the gene level, by restriction enzyme analysis of the DNA.

Biology - 1982

• Despite further wholesale relaxations of the NIH guidelines, a move to make compliance voluntary failed.

Biology - 1982

• Cloned rat growth hormone genes were injected into mouse zygotes, producing "supermice" that were twice the normal weight.

Biology - 1982

• Human insulin produced by recombinant DNA methods was marketed under the name Humulin.

Biology - 1982

• A foreign gene incorporated into the cells of a tobacco plant was shown to be transmitted in ordinary Mendelian fashion through the gametes.

Biology - 1982

• A human cancer gene, isolated from bladder cancer cells, is cloned in Escherischia coli. The base sequence of the cancer gene is found to differ from the same locus in a normal cell by a single base pair which causes a substitution of an amino acid in the resulting protein.

Biology - 1982

• An entirely new syndrome, characterized by severe impairment of the immune system, is recognized and given the name acquired immunodeficiency syndrome or AIDS.

Biology - 1983

• The complete 48,502 base pair sequence of the DNA of bacteriophage lambda is published.

Biology - 1983

• Kary B. Mullis invents the polymerase chain reaction (PCR), a method for rapidly and easily cloning DNA fragments.

Biology - 1984

• César Milstein, Georges J.F. Kohler, and Niels Kai Jerne are awarded the Nobel Prize for their work in developing techniques for producing monoclonal antibodies.

Biology - 1987

• Susumu Tonegawa wins the Nobel Prize for his work in the genetic mechanisms of antibody production.

Biology - 1993

• Kary B. Mullis is awarded the Nobel Prize for the polymerase chain reaction.

Biology - 1993

• Michael Smith is awarded the Nobel Prize for his discovery of site-directed mutagenesis