cell structure and discovery
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Answer:
Cell is discovered by Robert Hooke in 1800.
- Cell is of two type basis of nucleus- eukaryotic cell and prokaryotic cell.
- Cell is of two type basis of body-animal cell and plant cell.
- Cell is of two type basis of numbers of cells present in body- unicellular and multicellular.
Cell is basic and structural fundamental unit of life.
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There are many discoveries that have changed the course of science and the world. Nikola Tesla’s discovery of alternating currents, for example, helped pave the way for widespread access to electricity, and Louis Pasteur’s discovery that heat and disinfectant could kill bacteria improved food safety and saved millions of lives. In 1655, the English scientist Robert Hooke made an observation that would change the study of biology forever. While examining a thin, dried section of cork tree with a crude light microscope, Hooke observed that he could plainly see the cork to be made up of tiny spaces surrounded by walls, much like a honeycomb, but that the spaces were irregular and shallow (Figure 1). Further, Hooke noted that these "little Boxes" were so numerous that there were "in a square Inch above a Million... and in a Cubick Inch, above twelve hundred Millions [sic]" (Hooke, 1655).
The cork described in Micrographia by Robert Hooke
Figure 1: The cork described in Micrographia by Robert Hooke.
In his landmark book Micrographia, Hooke called these spaces "cells" because they resembled the small rooms monks lived in (cella in Latin). What Hooke’s samples were not able to reveal at the time, though, was that cells are not in fact empty. Though he was diligent in looking at his samples through different magnifications and with various light sources and angles, there were two major obstacles that stood in Hooke’s way of discovering subcellular structures. The first was that the microscope he was using at the time was still too low of a magnification to show that much was contained within the walls of the cells. The second: His samples were of cork – composed of long-dead cells, absent of any cytosol or organelles.
Antony van Leeuwenhoek improves microscopy
In the years immediately following, other scientists would build on the work of Hooke, including Antony van Leeuwenhoek (1632 – 1723), a cloth merchant in Delft, Nederland. Van Leeuwenhoek was not a scientist by formal training, but he was an industrious and curious individual who took great joy in observing the world around him (Anderson, 2009). While working in his haberdashery in the 1670s, van Leeuwenhoek began to experiment with glass-blowing and the construction of microscopes (Figure 2). Using the designs described by Hooke in Micrographia, van Leeuwenhoek built his own microscopes by hand, fabricating every element from the highly-refined lens to the screws used to hold the instrument together (Anderson, 2009).
van Leeuwenhoek's simple microscope
Figure 2: van Leeuwenhoek's simple microscope. On the brass plate is a small magnifying lens mounted and a sharp point that would hold the specimen. Turning the screws would adjust the position and focus.
During his lifetime, van Leeuwenhoek constructed hundreds of microscopes and lenses by hand, each one unique. It was with these microscopes and improved lenses that he began to study the world around him and share these observations with institutions like the English Royal Society. One of his first important observations came in August 1674, when he looked at water samples from Berkelse Meer, a lake two miles outside of Delft. In a letter to Henry Oldenburg that September, and published in Philosophical Transactions of the Royal Society, van Leeuwenhoek noted:
I took up some of it [the water] in a Glass-vessel which having viewed the next day, I found moving in it several Earthy particles, and some green streaks, spirally ranged, ... among all of which there crawled abundance of little animals some of which were roundish; those that were somewhat bigger than others were of an Oval figure: On these latter I saw two legs near the head and two little fins on the other end of their body…. The motion of most of them in the water was so swift, and so various, upwards, downwards, and round about, that I confess I could not but wonder at it. I judge, that some of these little creatures were above a thousand times smaller than the smallest ones, which I have hitherto seen.
What van Leeuwenhoek was seeing, we can now presume, were some of the smallest forms of life: protozoa, rotifers, ciliates, and phytoplankton. Van Leeuwenhoek’s descriptions are among the first to identify the unique features of these different microscopic organisms and was the beginning of the discipline we now call microbiology – the study of microscopic organisms.
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