GK/General Awareness/G-Studies,

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Biology

Cell – The Basic Unit of Life

1-Before the first microscope was invented around 350 years ago, people were not aware of the living world that was not visible to the naked eye.

2-Anthony van Leeuwenhoek (1632– 1723) in 1674 was the first human to see living bodies like bacteria, yeast, protozoa, Red Blood cell and the teeming life in a drop of water.
Antonie van Leeuwen hook was the first to see living bodies under microscope which he had contructed him self

3-It was in the year 1665 that Robert Hooke , a British scientist, observed thin slices of cork(soft bark from Oak tree) under a simple magnifying device which he had made himself.
Cells were first observed by Robert Hooke in 1665

4-The discovery of ‘cell’ by Robert Hooke was a milestone in the history of science.

5- Felice Fontana (1730–1805) (and few other scientists) first saw the nucleus in the epithelial cells (the outermost layer of the animal body) in the 18th century.

6-The boundary of a cell is the cell membrane. This gives a shape to the cell and selectively allows substances to pass through it, in or out of the cell.

7- There is another layer present over the cell membrane, known as the cell wall. This gives rigidity to the cell.

8-Cells are considered to be, ‘The structural and functional units of the living body’.

9- The jelly like substance between the nucleus and the cell membrane is called cytoplasm. It is a heterogeneous material. It contains membrane bound structures, called cell organelles, as well as more complex chemicals.

10-The size of the cells in living organism may be as small as the millionth of a meter (micron) or may be as large as a few centimeters.

11- The smallest cell 0.1 to 0.5 micrometers is found in Bacteria.

12- A human liver and kidney cell is 20 to 30 micrometer in size.

13-Human nerve cell is nearly about 90 to 100 cm.

14- The largest cell, measuring nearly 17 cm X 18 cm, is the egg of an Ostrich.

15-Robert Brown discovered nucleus in orchid leaf

16-Plant cells differ from those of animals in having an additional layer around the cell membrane termed cell wall.

17-Single celled animals are called unicellular organisms

Remember These –

1 Meter = 100 Centimeters (cm)

1 centimeter = 10 mille meters (mm)

1 millimeter = 1000 micro meters (µm)

1 micro meter = 1000 nano meters (nm)

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