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Microscopes and Cells Early Microscopes and the Cell Theory • Anton van Leeuwenhoek (1600’s) credited with the first microscope • Robert Hooke (1665) saw “cells” in woody plant tissue • Theodore Schwann (1839) saw cells in animal tissue Cell Theory • Between 1839 and 1855 the nucleus of the cell was seen for the first time – Hypothesis was that the nucleus was involved in cell reproduction – Many observations were made of cell reproduction – Led to statement of the cell theory Cell Theory • All living things are composed of cells • All cells come from preexisting cells by cell division • The cell theory applies to all organisms – Single cell organisms – Multicellular organisms (many start life as a single cell) Compound Microscope • • • • Major tool of modern biology Compound means more than one lens Ocular lens and objective lens Magnification is the product of magnification power or the ocular and the objective – (10X) times (40X) = 400X Compound Microscope • Limitations to use of compound microscope – Samples need to be transparent or have to reflect a great deal of light – Many sample need to be sliced into thin sections and stained – Sectioning and staining involves chemical changes to the sample – Resolution limited by wavelength of light Electron Microscope • Uses electron beam instead of light to examine the specimens • Magnification 1000X higher than the highest compound microscope • TEM and SEM • Specimen preparation is complex • Biologists study the pictures not the sample Can you? • What do you say to someone who says they saw a living organism in the electron microscope at Liberty Science Center? • What do you say to someone who says that intestine cells are pink, magenta and dark purple because that’s what they saw in the microscope? Two types of cells…. • Prokaryote – No nucleus • Eukaryote – Nucleus