Cell Theory: Origin, Meaning & Implications PDF

Cell Theory: Its Origin, Meaning and Implications ❖The discovery of cells arose from the invention and improvement of microscope in the 17th century. ❖Robert Hooke first to discover cells and coined the term “cell’ in 1665 from piece of cork under simple microscope, 300X magnification....

Cell Theory: Its Origin, Meaning and Implications ❖The discovery of cells arose from the invention and improvement of microscope in the 17th century. ❖Robert Hooke first to discover cells and coined the term “cell’ in 1665 from piece of cork under simple microscope, 300X magnification. ❖Anton van Leeuwenhoek 1670 - able to observe different types of cells, sperm, blood cells, and bacteria through a simple microscope which he built. Took more than 2 centuries (1838) before biologists could extend the work of early microscopists and understand the true significance of cells to the living state. ❖Matthias Schleiden (studied plant tissues) and Theodor Schwann (studied animal tissues) proposed the Cell Theory, may be seen as the birth of contemporary biology. FORMULATION OF THE CELL THEORY In 1839, Theodor Schwann & Matthias Schleiden published a book on animal and plant cells. They summarized their observations into three conclusions about cells: (1) The cell is the unit of structure, physiology, and organization in living things. (2) The cell retains a dual existence as a distinct entity and a building block in the construction of organisms. (3) Cells form by free-cell formation, similar to the formation of crystals (spontaneous generation). The correct interpretation of cell formation by cell division was finally promoted by others and formally enunciated in Rudolph Virchow's powerful dictum, "Omnis cellula e cellula"... "All cells only arise from pre-existing cells“. Robert Hooke’s simple Microscope 300x magnification  The minimum resolution of a light microscope is about 2 microns, the size of a small bacterium. Light microscopes can magnify effectively to about 1,000 times the size of the actual specimen. – At higher magnifications, the image blurs. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings THE MODERN TENETS OF CELL THEORY 1. All known living things are made up of cells. 2. Cell is the structural & functional unit of all living things. 3. All cells come from pre-existing cells by division. (Spontaneous Generation does not occur). 4. Cells contains hereditary information which is passed from cell to cell during cell division. 5. All cells are basically the same in chemical composition. 6. Energy flow (metabolism & biochemistry) of life occurs within cells. The Cell theory predates other great paradigms of biology: Darwin's Theory of Evolution (1859) Mendel's Laws of Inheritance (1865) Establishment of Comparative Biochemistry (1940) Profound revelations, led to greater understanding of the structures and processes that make up the living state.