Hi, Dosto! Biology padhte waqt sabse bada headache kya hota? Scientists are known for their names and discoveries, aren't they? Khaskar jab Class 11 syllabus khatam ho raha ho aur 12th shuru ho, dimag mein dates ki khichdi ban jati hai. The NCERT's line-by-line dates are a waste of time; instead, the appropriate "Biology Dates & Events Cheat Sheet" is posted. Isey bookmark kar lijiye, revision ke time yeh aapke bohot kaam aayegi

DATE / YEAR	EVENTS / DISCOVERIES
CLASS 11TH
1969	Five Kingdom Classification by R.H. Whittaker
1892	Virus was named and discovered by Dimitri Ivanowsky
1935	W.M. Stanley showed virus could be crystallized
1971	T.O. Diener discovered viroids
1838	Matthias Schleiden examined a large number of plants and observed that all plants are composed of different kinds of cell which form the tissues of the plant
1839	Theodore Schwann studied different types of animal cells and reported that cells had a thin outer layer which is today known as ‘plasma membrane’
1855	Rudolf Virchow explained that cells arises from pre-existing cells (Omnis cellula-e cellula)
1898	Camillo Golgi discovered golgi apparatus
1860	Julius von Sachs discovered hydroponics
1770	Joseph Presley revealed essential role of air in the growth of green plant
1774	Joseph Presley discovered oxygen
1854	Julius von Sachs provided evidence for the production of glucose when plants grow
1905	Blakman’s law of limiting factor
1926	Gibbrellic acid was discovered by E. Kurosawa
1955	Miller et al. identified and crystallized cytokinins
MID 1960S	Inhibitor-B, abscission II and dormin were reported
1910	H.H cousins discovered ethylene
CLASS 12TH
1951	Family Planning
1971	Medical Termination of Pregnancy (MTP)
1856--1863	Gregor Mendel Experiments
1865	Mendel published his work on inheritance of characters (but remained unrecognized till 1900)
1900	Rediscovery of Mendel’s results on inheritance of characters by de Vries, Correns, and von Tschermak
1902	Walter Sutton and Theodore Boveri proposed Chromosomal theory of inheritance
1891	Henking traced a specific nuclear structure all through spermatogenesis to understand mechanism of sex-determination
1866	Langdon described Down’s syndrome
1869	Friedrich Meischer identified DNA as an acidic substance in nucleus and named it “Nuclein”
1953	James Watson and Francis Crick proposed double helix structure of DNA
1928	Transforming principle by Fredrick Griffith
1933-44	Biochemical characterization of Transforming principle by Oswald Avery, Colin MacLeod and Maclyn McCarty
1952	Unequivocal proof that DNA is genetic material by Alfred Hershey and Martha Chase
1953	Watson and Crick proposed semiconservative DNA replication
1958	Experimental proof for semiconservative DNA replication by Matthew Meselson and Franklin Stahl
1990-2003	Human Genome Project (HGP)
38838	Sequence of Chromosome-1 was completed
20 billion years	Age of universe
4.5 billion years	Age of earth
4 billion years back ( 500million years after formation of earth)	Life appeared on earth
1953	Miller Urey experiment
3 billion years back	The first non-cellular life originated
2000 million years back	First cellular form of life appeared
1920	The phenomenon of natural selection observed after industrialization in England
500mya	Invertebrates were formed and active
350 mya	Jawless fish evolved
320 mya	Sea weeds and few plants existed
350mya	Fish with stout and strong fins could move on land and go back to water
1938	Coelencanth was caught in South Africa
200mya	Some of the land reptiles (Ichthyosaurs) went back into water to evolve into fish like reptiles
about 65mya	Dinosaurs suddenly disappeared from earth
15mya	Origin of Dryopithecus and Ramapithecus
3-4mya	Australopithecus
2mya	Homo habilis
1.5mya	Homo erectus (Java man)
100,000--40,000 years ago	Homo sapiens neanderthalesis (Neanderthal man)
75,000--10,000	Homo sapiens (Modern man)
1981	AIDS was first reported
mid 1960s	Green revolution
1960--2000	▪ Wheat production increased from 11 million tons to 75 million tons ▪ Rice production increased from 35 million to 89.5 million tons
1963	Semi-dwarf varieties of wheat – Sonalika and Kalyan Sona were introduced in India
2000	Maize hybrids having twice the amount of amino acids, lysine and tryptophan were developed
1950s	Totipotency
1972	Construction of first Recombinant DNA by Stanley Cohen and Herbert Boyer
1963	Two enzymes responsible for restricting the growth of bacteriophage in Escherichia coli were isolated
1990	First gene therapy given to a four year old girl with ADA deficiency
1997	The first transgenic cow, Rosie, produced human protein-enriched milk (2.5 grams per litre)
1920s	The prickly pear cactus introduced into Australia
1992	“The Earth summit” – Rio de Janeiro