Cell Structure and Functions Class 8 PPT

 Page 1


CHAPTER - 8 
 
CELL – STRUCTURE AND FUNCTIONS 
Page 2


CHAPTER - 8 
 
CELL – STRUCTURE AND FUNCTIONS 
1) Discovery of the cell 
    In 1965 Robert Hooke observed slices of cork from the 
bark of a tree under a simple magnifying glass. He noticed 
small boxes or compartments in the cork slice. The boxes 
were separated from each other by a wall or partition. He 
named each box as a Cell. The cells which Hooke observed 
were actually dead cells of plants. 
Page 3


CHAPTER - 8 
 
CELL – STRUCTURE AND FUNCTIONS 
1) Discovery of the cell 
    In 1965 Robert Hooke observed slices of cork from the 
bark of a tree under a simple magnifying glass. He noticed 
small boxes or compartments in the cork slice. The boxes 
were separated from each other by a wall or partition. He 
named each box as a Cell. The cells which Hooke observed 
were actually dead cells of plants. 
2) The Cell 
    Cells are the basic structural units of living organisms. 
    Some organisms are made up of a single cell and some are made up 
of many cells.  
    The number of cells in a tall tree or an animal like an elephant or 
human being are billions and trillions of cells. 
    Organisms made up of many cells are called multicellular organisms. 
Eg: a tree, an elephant. 
    Organisms made up of only one cell are called unicellular organisms. 
Eg: amoeba, paramaecium. 
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CHAPTER - 8 
 
CELL – STRUCTURE AND FUNCTIONS 
1) Discovery of the cell 
    In 1965 Robert Hooke observed slices of cork from the 
bark of a tree under a simple magnifying glass. He noticed 
small boxes or compartments in the cork slice. The boxes 
were separated from each other by a wall or partition. He 
named each box as a Cell. The cells which Hooke observed 
were actually dead cells of plants. 
2) The Cell 
    Cells are the basic structural units of living organisms. 
    Some organisms are made up of a single cell and some are made up 
of many cells.  
    The number of cells in a tall tree or an animal like an elephant or 
human being are billions and trillions of cells. 
    Organisms made up of many cells are called multicellular organisms. 
Eg: a tree, an elephant. 
    Organisms made up of only one cell are called unicellular organisms. 
Eg: amoeba, paramaecium. 
3) Shape of cells 
    Cells are of different shapes. 
    Some cells keep changing their shape. Eg : amoeba, 
white blood cells in human beings. 
    Some cells are spherical, round, elongated, spindle 
shaped, or branched. 
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CHAPTER - 8 
 
CELL – STRUCTURE AND FUNCTIONS 
1) Discovery of the cell 
    In 1965 Robert Hooke observed slices of cork from the 
bark of a tree under a simple magnifying glass. He noticed 
small boxes or compartments in the cork slice. The boxes 
were separated from each other by a wall or partition. He 
named each box as a Cell. The cells which Hooke observed 
were actually dead cells of plants. 
2) The Cell 
    Cells are the basic structural units of living organisms. 
    Some organisms are made up of a single cell and some are made up 
of many cells.  
    The number of cells in a tall tree or an animal like an elephant or 
human being are billions and trillions of cells. 
    Organisms made up of many cells are called multicellular organisms. 
Eg: a tree, an elephant. 
    Organisms made up of only one cell are called unicellular organisms. 
Eg: amoeba, paramaecium. 
3) Shape of cells 
    Cells are of different shapes. 
    Some cells keep changing their shape. Eg : amoeba, 
white blood cells in human beings. 
    Some cells are spherical, round, elongated, spindle 
shaped, or branched. 
4) Size of cells 
   Cells in living organisms are of different sizes. They may be as small 
as millionth of a meter (micrometre or micron) or large as a few 
centimetres. 
   The smallest cell is the cell of bacteria (0.1 to 0.5 micrometre). 
   The largest cell is the egg of an ostrich (17cm x 13cm).