LECTURE-2-CELL-THEORY33333333333333333333333333.pptx

theory about cells

1. CELL THEORY

2. Where do cells come from?

3. The discovery of cells was made possible by the development of the microscope in the 17th century.

4. Development of Cell Theory

5. Zacharias Janssen Dutch spectacle-maker Zacharias Janssen invented a primitive microscope with the help of his father, Hans. This microscope would later be used by Marcello Malpighi and Robert Hooke.

6. Robert Hooke An English scientist, used a microscope to examine a thin slice of cork. Hooke described it as consisting of “a great many little boxes.” These “little boxes” reminded him of the cubicles or “cells” in which monks lived, so he called them cells.

7. Anton van Leeuwenhoek Upgraded Janssen’s microscope and produced his own lens. Some of his lenses could magnify objects up to 270x diameters. With this invention, he discovered mobile organelles in many subjects which he called “animalcules.”

8. Robert Brown Scottish botanist, made a series of discoveries about cell organelles and ultimately discovered the nucleus. This became a major breakthrough in the history of biology.

9. Matthias Schleiden microscopically examined plants and recognized that plant parts come from cells. In his writings in Contributions to Phytogenesis , he proposed that the different structures of plant are all composed of cells.

10. Theodor Schwann declared that animals are likewise composed of cells. This put an end to the debates- whether or not plants and animals are different in structural origin and composition.

11. Albrecht von Roelliker Swiss embryologist, stated that sperm and egg are composed of cells and that all humans are configured from cells. This initiated the idea that most life forms are made up of cells and gave the scientific community a flourishing understanding of biology.

12. Louis Pasteur French microbiologist, he developed fermentation, , a process to kill bacteria, he proved that bacteria are able to multiply, and that bacteria’s cells come from other bacterial cells.

13. Rudolf Virchow declared “ Omnis cellula e cellula ,” which mean that cells come from preexisting cells. With this conclusion, the cell theory was completed.

14. Cell Theory The cell theory developed in the mid-1800s because of the various discoveries about cells. Generally, it states the following three fundamental postulates: 1. The basic unit of life is the cell. 2. All organisms are made of cells. 3. All cells arise from pre-existing cells.

15. First postulate: The basic unit of life is the cell. This statement simply explains – in order that an organism may be considered living, it must have a cell. Some organisms may be unicellular or one-celled, such as bacterium ( Streptococcus pneumoniae ); or multicellular or multi-celled, such as animals. One proof that an organism is alive just by looking at its cells is the movement of the organelles inside it.

16. Second postulate: All organisms are made of cells. The declaration that all organisms are made up of cells was a collaboration between a botanist and a physiologist (Matthias Schleiden and Theodor Schwann).

17. Third postulate: All cells arise from pre-existing cells. German scientist Rudolf Virchow introduced the third tenet of the cell theory: “ Omnis cellula e cellula ”. He noticed that the existence of diseases in the organs and tissues come from affected cells.