IN GUJARATI (click on the arrow)

Important Years and Facts in Biology (NCERT Focus)

Introduction

This note is designed to help you revise important years, discoveries, and numerical facts in Biology, particularly relevant to the NCERT curriculum. Memorizing these key points can be crucial for exams. This note is structured for clarity and easy revision, using bold text to highlight essential information. Let's dive in!

Important Discoveries and Events by Year

This section chronologically lists significant discoveries, events, and experiments in Biology, along with the corresponding year and key scientists involved.

• 1770: Joseph Priestley conducted a pivotal experiment using a bell jar, mice, and a mint plant alongside a candle. This experiment was crucial in understanding the role of plants in air purification.
• 1774: Joseph Priestley is credited with the discovery of oxygen.
• 1838: Matthias Schleiden, a German botanist, concluded that all plants are composed of different kinds of cells which form the tissues of the plant.
  • 1839: Theodore Schwann, a British zoologist, reported that animal cells also had a cell membrane and his studies on plant tissues concluded that cell wall is a unique character of the plant cell. Together, Schleiden and Schwann formulated the cell theory.
• 1854: Julius von Sachs demonstrated that glucose is produced during photosynthesis and is stored as starch within plant cells. He also showed that chlorophyll is located in special bodies (chloroplasts) within plant cells and that green parts of plants produce glucose.
• 1855: Rudolf Virchow extended the cell theory by stating "Omnis cellula e cellula," meaning new cells arise from pre-existing cells. This completed the Cell Theory.
• 1856 - 1863: Gregor Mendel conducted his groundbreaking experiments on garden peas, laying the foundation for the laws of inheritance.
• 1865: Gregor Mendel's work on inheritance of characters was published, though it initially went largely unnoticed.
• 1866: Down's Syndrome was discovered and described by Langdon Down.
• 1869: Friedrich Miescher first identified DNA as an acidic substance in the nucleus and termed it "Nuclein."
• 1891: Several significant discoveries were made:
  • Fossils of Java Man (Homo erectus) were discovered in Java, providing crucial evidence in human evolution.
  • Henking discovered the X-body (later identified as the X-chromosome) in insects, contributing to the understanding of XO-type sex determination.
• 1892: D.J. Ivanowsky discovered the Tobacco Mosaic Virus (TMV), recognizing viruses as a new type of infectious agent smaller than bacteria.
• 1898: Further advancements in virology and cell biology:
  • M.W. Beijerinck demonstrated the infectious nature of the Tobacco Mosaic Virus (TMV), coining the term "Contagium vivum fluidum" (infectious living fluid).
  • Camillo Golgi discovered the Golgi Body (Golgi apparatus) within cells.
• 1900: Rediscovery of Mendel's Work: Mendel's laws of inheritance were independently rediscovered by Hugo de Vries, Carl Correns, and Erich von Tschermak, bringing Mendel's work to the forefront of biology.
• 1902: The Chromosomal Theory of Inheritance was proposed by Sutton and Boveri, linking Mendel's factors (genes) to chromosomes.