CBSE Class 9 Science The Cell Exam Notes. Please refer to the examination notes which you can use for preparing and revising for exams. These notes will help you to revise the concepts quickly and get good marks.
In 1665, Robert Hooke observed the cell in a cork slice with the help of a primitive microscope. He saw that cork resembled the structure of a honey comb consisting of many little compartments. Robert Hooke called these boxes cells. Cell is a Latin word for 'little room.'
Unicellular And Multicellular Organisms
All living organisms are made up of one or more cells. On the basis of cell number, organism are grouped into 2 categories -
Unicellular organisms :
* Organism in which a single cell make the whole body. For example, Amoeba, Paramecium, bacteria & Chlamydomonas.
Multicellular organism :
* Organism in which body contains more than one cell. For example - Plante, animals & fungi.
Cell Size :
* The size of different cells ranges between broad limits.
* Some plants and animals cells are visible to the naked eye.
* Most cells are visible only with microscope.
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