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Robert Hooke ( ) ◦ Designed microscopes ◦ Discovered and documented the first “cells” in 1665 Named them after the cells in which a monk sleeps.
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Cell Discovery & Cell Theory
It all started with an invention….
The first microscope◦Zacharias Jansen, 1595,
Middleburg, Holland◦It launched great leaps in
Astronomy and Biology. ◦Some of the first great
observations with it were made by…
Robert Hooke (1635-1703)
◦Designed microscopes◦Discovered and
documented the first “cells” in 1665
Named them after the cells in
which a monk sleeps.
Robert Hooke (1635-1703)
Released book of detailed drawings and observations: Micrographia, 1665
Drawing of Flea
Hooke had a life-long rivalry with Sir Isaac Newton. Newton worked hard to destroy his reputation during and after his death. Much of Hooke’s work was destroyed – even his gravesite is still unknown.
Images from Micrographia
Images from Micrographia
Images from Micrographia
Antony van Leeuwenhoek (1632-1723)
A tradesman from Holland who became fascinated with Hooke’s book
Discovered bacteria, protists, sperm cells, blood cells, nematodes, etc.
Became an expert lens grinder and made over 500 simple microscopes
Acute eyesight and lens grinding skill let him build microscopes that were capable of 200X magnification
Cell Theory1838 Mattias Schleiden stated that
all plant tissues consisted of cells1839 Theodore Schwann stated that
all animal tissues consisted of cellsEach conjectured that there was a
nucleus1858 Rudolf Virchow combined the
two ideas and added that all cells come from pre-existing cells, formulating the Cell Theory
Rudolf Virchow 1858
Cell Theory
All living things are composed of one or more cells
In organisms, cells are the basic units of structure and function.
All cells are produced only from existing cells.
Modern Microscopes
Some of the light microscopes here are capable of 1000x magnification.◦ That is about the limit of a light microscope’s magnification
without losing clarity (called Resolving Power). Due to the width of visible light’s wavelength
The electron microscope was introduced in the 1950s and uses the wavelength of electrons to increase the resolving power by 100x. ◦ Approx. 100,000x magnification!!◦ Cell Biology advanced rapidly as cellular organelles were clearly
seen for the first time.
Resolving Power
Transmission Electron Microscope (TEM) magnifies a slice of a sample. (Rabbit trachea cilia)
Scanning Electron Microscope (SEM) shows 3D image of the Rabbit trachea cilia
Modern Microscopes
A few limitations of electron microscopes
• Specimen must be placed in a vacuum and is typically coated with a conductive metal like gold. Consequently you can’t look at living specimens under electron microscopes.
• All images produced are black and white, so you can’t distinguish colors. Pictures are usually colored in digitally later.
Other Cool SEM pictures
http://www.telegraph.co.uk/science/picture-galleries/7924099/Creepy-crawlies-Amazing-Scanning-Electron-Microscope-pictures-of-insects-and-spiders.html
Carbon atoms bonded to hydrogen
Fruit fly with four eyes under an SEM
Vocabulary: Cell HistoryJansen Light MicroscopeHooke Electron MicroscopeVan LeeuwenhoekSchleiden SchwannVirchowCell TheoryResolving Power