Microscopes—tools for studying biodiversity
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Microscopes—tools for studying biodiversity
• detect, distinguish between organisms
• study structure of cells, tissues, organs
• determine locations of molecules
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simple microscope
• 1 lens (eg magnifying glass)
• bends light so object appears larger
virtual image object lens eye
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compound microscope
• >1 lens
• mag multiplies• so do optical problems
object obj. virtual eyepiece eye lens image (ocular)
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optical terms
• magnification: how large appears compared to actual size
• resolution (resolving power): closest distance 2 objects can be, & still be distinguished as separate obj.
• resol dep on wavelength ()– shorter better. electron microscopes
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lens resolution comparison
• human eye 0.2mm ruler in lab• light scope 0.2m 1000x better than
eye• electron scope ~ 2 nm 100x better than LM
100,000x better than eye
= micro• LM = light scope• EM = electron scope
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scale
• 1mm = 1000 m = 1 million nm• human hair ~1/10 of mm = 100 m
• electron microscopy reveals viruses! 20 – 90 nm
• 1990s: 50 million/mL of seawater, soil
• Fig 6.2, p 95
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image terms
• photograph--no scope• photomicrograph--photo taken
though scope– light micrograph– electron micrograph
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LM
• Advantage: living cells & organisms
• colors (pigments)• movement• focus through depth of specimen
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EM
• disadvantage: specimens dead
• electrons from filament • in vacuum• focus with electromagnetic lenses
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TEMtransmission electron microscope
• electrons go through specimen
• make shadow• fine structure
inside of cells• many sections for
3-D structure
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TEM
• can locate molecule w/antibody attached to gold particle
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SEM scanning electron microscope
• electron beam scans specimen
• specimen electrons collected
• surface of object• 3-D view
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LM contrast
• pigments• stains• brightfield--standard bright background• special techniques (Fig 6.3, p 96)
– polarized light– darkfield– differential interference contrast (dic)– phase contrast
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fluorescencemicroscopy
• UV light source• specimen
emits light
• autofluorescence• tagged antibodies• reporter proteins
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Confocal microscopy
• laser light source
• optical sections
• no out of focus blur
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discovery of cells
• 1665 English scientist Robert Hooke
• first saw (cork) cells [cell = room]• compound microscope• (30x mag)• Royal Society, London
Hooke’s drawing of cork cells in Micrographiahttp://www.gutenberg.org/files/15491/15491-h/15491-h.htmsection 18, plate 11
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Hooke’scompound microscop
e
http://www.arsmachina.com/hooke.htm
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scientific literature
• primary lit. — original report of research– intro, materials & methods, results, discussion
• peer-reviewed
• secondary lit. — report about primary lit.
• ProcRSocL, Nature, PNAS, Science
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discovery of microorganisms
• 1674 Dutch merchant Antony van Leeuwenhook
• first saw “animalcules”• protists, and later bacteria• simple microscope w/great lens• 275-295x mag
http://www.ucmp.berkeley.edu/history/leeuwenhoek.html
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discovery of microorganisms
• 1676 Leeuwenhookwrote to Royal Society
@ singled celled organisms
• Hooke confirmed• first published bacteria• voucher specimens
http://www.ucmp.berkeley.edu/history/leeuwenhoek.html
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Leeuwenhoek’s microscope
http://www.brianjford.com/wav-mict.htm
light micrograph of red blood cells photographed through this scope
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• mid 1700smicroscopy popular science