Siyavula: Life Sciences Grade 10 - Cd3wd.com

24 CHAPTER 1. LIFE AT THE MOLECULAR, CELLUAR AND TISSUE LEVEL• Cells contain hereditary information (DNA) which is passed from cell to cell during cell division.• Unicellular organisms are made up of one cell. Multicellular organisms are composed of multiple cells.Follow the url below to view an interactive timeline of the history of cell theory and the role microscopesplayed in in early cell theory :http://www.tiki-toki.com/timeline/entry/11813/The-history-of-cell-theory/ (made bykatie - all images are attributed or public domain, the basic dates are from:http://en.wikipedia.org/wiki/Timeline_of_microscope_technology 10 )Types of microscopyType of microscopeDening characteristicLight microscopy visible light (photons) are transmittedthrough or reected from a specimen. -http://en.wikipedia.org/wiki/Light_microscopy#Optical_microscopyElectron microscopy In an electron microscope, a beam 18 of electrons 19is used to illuminate the object. This allows muchhigher resolution than the light-powered opticalmircroscope because electrons have much shorterwave lenghts than visible light (photons).Scanning electron microscope SEM looks at thesurface of bulk objects by scanning the surfacewith a ne electron beam and measuring reection(wikipedia)A transmission electron microscope (TEM) are usedto produce images of the inner structure of a specimensince electrons are transmitted through thespecimen.Table 1.5How to use a light microscope can be viewed at http://www.youtube.com/watch?v=FuDcge0Zuak 20Light microscope:10 http://en.wikipedia.org/wiki/Timeline_of_microscope_technology17 http://en.wikipedia.org/wiki/Light_microscopy#Optical_microscopy18 http://en.wikipedia.org/wiki/Particle_beam19 http://en.wikipedia.org/wiki/Electron20 http://www.youtube.com/watch?v=FuDcge0Zuak