THE-EVOLVING-CONCEPT-OF-LIFE (2)

Introduction to Life Sciences

  • Concept evolution: Introduction to life sciences has changed as scientific knowledge advances and discoveries are made in cellular biology.

What is a Cell?

  • Definition: The basic unit of all organisms and the building blocks of life.

Discovery of Cells

  • Robert Hooke (1665):

    • Described microscopic compartments in cork, naming them "cells" from the Latin word "cella" meaning "small room."

    • Observed boundaries of plant cells, known as the "cell wall."

Robert Hooke's Contributions

  • Inventions: Invented the compound microscope with a light illuminator that was used to study microorganisms in the Royal Academy, London.

  • Collaborations: Worked alongside notable scientists including Christian Huygens, Christopher Wren, Robert Boyle, and Isaac Newton.

Important Years in Microscopy and Biology

  • 1267: Roger Bacon described magnification in articles in "Perspectiva."

  • 1538: Girolamo Fracastoro described magnification in "Homocentrica."

  • 1590s: The Jansens (Jans Jansen, Zacharias Janssen, and Hans Lippershey) credited with the invention of the compound microscope.

Notable Observations (17th Century)

  • 1658: Athanasius Kircher noted the appearance of organisms from decaying animal bodies.

  • Jan Swammerdam: Observed frog embryos and described red blood cells.

  • 1665: Robert Hooke published "Micrographia," detailing findings including fleas and sponges.

  • 1668: Antonie van Leeuwenhoek studied "animalcules," observing microscopic organisms like protozoans and sperm cells.

Leeuwenhoek's Background

  • Professionally, Leeuwenhoek sold fabrics; he maintained a hobby of grinding lenses and microscopy that led to significant discoveries. He is known for achieving high magnification (up to 300x) and detailed observations.

  • Authored 375 articles in the Philosophical Transactions and 27 articles in the Memoirs of the Paris Academy of Sciences.

Microbiological Discoveries and Experiments

  • 1740s: John Tuberville Needham studied how microorganisms appear, proposing they arise from non-pre-existing ones.

    • Heating infusions and observing growth led him to this conclusion.

  • Lazzaro Spallanzani refuted Needham, proving that sufficient heating kills microorganisms, thereby establishing that life comes from pre-existing life.

Development of Cell Theory

  • 1831: Robert Brown recognized the nucleus and its importance across various cell types.

  • 1838: Matthias Jacob Schleiden proposed that all plant structures consist of cells.

  • Theodore Schwann stated that all animal tissues are composed of cells, leading to the formulation of the cell theory.

Advances in Cell Biology (19th Century)

  • 1850: Multiple scientists, including Robert Remak, Rudolf Virchow, and Albert Kolliker, refuted Schleiden's claim regarding nucleus formation from "cytoblast," confirming the theory on cells arising from pre-existing cells and introducing "cytoplasm."

  • 1897: Enhancements in techniques such as staining, microtomy, and microscope improvements led to the discovery of new cellular components, including the endoplasmic reticulum.

  • 1898: Carl Benda discovered the mitochondrion; Camilo Golgi discovered the Golgi apparatus.

  • 1882: Walther Flemming studied chromatin and coined the term "mitosis," observing chromosome division.

  • 1888: The term "metaphase" coined by Wilhelm Weldeyer, with subsequent stages of the cell cycle studied in various organisms.