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