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Published on 09 Feb 2013 | over 4 years ago

With the help of a microscope, an English scientist, Robert Hooke, first discovered the existence of cells in 1665.Scanning electron microscopes are used to examine the external parts of various organisms.The transmission electron microscope is used to view the internal structure of a cell and its organelles.Organisms that are made up of a single cell and perform all their vital activities, like reproduction, locomotion and digestion, are called unicellular organisms.Organisms that are made up of more than one cell are called multicellular organisms.Amoeba uses small finger-like projections called pseudopodia for locomotion and to capture prey.Paramecium is a single cell and is built in such a way that it performs all its vital activities, like reproduction, locomotion, digestion, and so on. Read more at learnnext.com/lesson/CBSE-VIII-Science-Introduction-to-Cells.htm

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