Discovery of Cell
In 1665, an English biologist Robert Hooke invented
first compound microscope and observed the sections of corks and leaves under
this microscope. He noticed in them small box like chambers of same size which
he called “cells”. After this, biologists observed different organisms under
the microscope. They found that structure of cells was complex.
Cell Theory
In 19th century, the compound microscope was highly
advanced and biologists observed things just a micrometer apart. After this, a
series of discoveries started, which provided basic information for cell
theory.
1. In 1831 – 33, Robert Brown discovered nucleus in cells of plants.
2. In 1838, a German botanist Mathias Scheiden observed that all plants were
made up of cells.
3. In 1839, Theoclor Schwann obsrved that the bodies of of animals were made up
of cells which were similar to plant cells.
4. Thus, Schleiden and Schwann formulated the “Cell Theory”. According to this,
all organisms are made up of cells.
5. In 1840, J. Purkinji gave the name “Protoplasm” to the things found inside
the cells. At that time, cell was considered as a bag of thick dense substance
containing a nucleus.
Later on, resolving power and quality of microscopes were highly improved.
Section cutting of tissues and cells and their staining became easier and
better. It revealed that cell was not a simple mass of granular substance;
instead it contained many sub cellular bodies called “Organelles”. Each
organelle has a definite job in the cell.
6. Human is made up of about 60 trillion cells. From Amoeba and unicellular
algae to whales and tallest red wood trees, all’ are made up of similar basic
units called cell. All animals and plants are thus made up of cells and cell
products.
Salient Features of Cell
Theory
1. All animals and plants are made up of cells and
cell products. Among these some organisms are unicellular and some are
multicultural.
2. Cell is structural and functional unit of living organisms.
3. New cells come from the divisions of pre-existing cell.
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