Biology class 9th ( Fundamental unit of life) cell part-01

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                         Biology

                                                    Class - 9

                                    Part - 1

        The Fundamental Unit Of Life


    # Events related to cytology


  • Study of cell : Cytology


  • Discovery of non-living cell : Robert Hooke ( 1665 )


  • Discovery of living cell : Antony Leeuwenhoek ( 1674 )


  • Discovery of protoplasm : Purkinje (1839 )


  • Cell theory was given by : Schleiden ( 1838 ) and Schwann ( 1839 )


  • Rudolf virchow expanded cell theory in : 1855

 

    # What are living organisms made up of ?


  • All living organisms are made up of cells.


  • Best on the number of cells present in an organism divided into two parts : 


  • Unicellular organisms : Made up of only one cell.


  • Multicellular organisms : Made up of more than one cell.


#Shape and size of the cells : The shape and size of the cells are related to the specific function they perform.


  • Some cells can change their shape, like amoeba and white blood cells.


  • Most of the plant cells and animal cells have a fixed shape.


# Cells which are fixed in shape can be


  • Polygonal : ex - liver cells


  • Spherical : ex - eggs of many animals


  • Spindle shaped : ex - smooth muscle fibre


  • Elongated : ex - nerve cells


  • Discoidal : ex - erythrocytes


  • Cuboidal : ex - germ cell


  • Stellate : ex - bone cell


  • Elliptical : ex - fat cell


# Cell size : most cells however are visible only under microscope since they are only a few micrometres in diameter.


  • Size of bacteria cell : 0.1-0.5 um.    ( 1um = 10^-6 m )


  • Biggest cell : 18 cm


  • The prokaryotic cells usually range between 1 to 10 um.


  • The eukaryotic cells usually range between 5 to 100 um.


  • The size of an organism is dependent on the number of cells present and not on the size of cells.


  • The elephant is larger due to the large number of cells present in its body as compared to rats.





Next part......Click here 👉👉 Fundamental unit of life ( cell) part-02







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