Class notes Biology class 9

CLASS 9th NOTES

SCIENCE
FUNDAMENTAL UNIT OF LIFE:CELL
PRASHANT KIRAD

, PRASHANT KIRAD

FUNDAMENTAL UNIT OF LIFE: CELL
Cell:
It is known as the structural and fundamental unit of life because it
is the basic building unit of an organism and is capable to perform
basic functions of all living organisms.
Cytology is the scientific study dedicated to understanding the
structure and composition of cells.
In 1665, Robert Hooke first observed cells in a thin slice of cork,
marking the beginning of our understanding of cellular existence.
A. V. Leeuwenhoek, in 1674, made the groundbreaking discovery of
the first free-living cell.
Protoplasm, the essential substance within cells, comprises water,
ions, salts, organic molecules, cell organelles, and a nucleus, existing
in sol-gel states. 10
Discovery of Living Cell Anton Van Leeuwenhock (1674)
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Discovery of Nucleus Robert Brown (1831)
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Discovery of Protoplasm J. E. Purkinje (1839)
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Cell Theory:
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The cell theory was given by Schleiden and Schwann, in 1838 which
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states that:
1. All living things are made up of cells.
2. The cell is the basic unit of structure and function in living
organisms.
3. Cells come from pre-existing cells through the process of cell
division.




onion peel cell

, PRASHANT KIRAD




Types of Cells and Organisms

On basis of number of cells:
On the basis of number of cells, organisms are divided into two
categories: 10
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On the basis of type of organizational cells:
1. Prokaryotic Cells
2. Eukaryotic Cells