Cells & Microscopes
Contributors to the Cell Theory Robert Hooke (1665) viewed cork cells under microscope; named cells Anton van Leeuwenhoek (1673) viewed living cells with a microscope
Mattias Schleiden (1838) discovers that plants are made of cells Theodor Schwann (1839) discovers that animals are made of cells Rudolf Virchow (1855) stated that cells come only from other cells
The Cell Theory All organisms are composed of one or more cells. Unicellular: one-celled Multicellular: many-celled
The cell is the basic unit of organization of all organisms. cells organism organ system tissue
All cells come from preexisting cells.
Two Basic Cell Types Prokaryotes Simple Ex. bacteria No membrane-bound organelles No nucleus Found only in unicellular forms Ex. bacteria
Two Basic Cell Types Ex. algae, fungi, plants, animals Eukaryotes Complex Have membrane-bound organelles Have a nucleus Found in both uni- and multicellular forms
Cell Comparison
ALL Cells Have . . . Cell membrane Cytoplasm DNA Ribosomes
Introduction to the Microscope Care Parts Focusing Students will have their microscopes out, for reference as we go through each of the steps. As an introduction, students will be asked what kinds of things they can do with this tool.
Always carry with 2 hands Keep objects clear of desk and cords Microscope Care Always carry with 2 hands Keep objects clear of desk and cords Only use lens paper for cleaning Do not force knobs Always store covered Teacher demonstrates how to hold the microscope, where the lens paper is located and how to use it. Students will be invited to turn the knobs and observe the stage as it moves up and down. Teacher will demonstrate how to store the microscope.
Microscope Parts Eyepiece Body Tube Revolving Nosepiece Arm Objective Lens Stage Stage Clips Coarse Focus This is a similar version of the microscope used in class. Students will be identifying the parts on the microscopes at their desks as we go along and what their functions are. Diaphragm Fine Focus Light Base
Place the Slide on the Microscope Use Stage Clips Using the Microscope Place the Slide on the Microscope Use Stage Clips Start on Scanning (red) Power Look into the Eyepiece Use the Coarse Focus Click nosepiece to Low (yellow) Power Give students a slide from the “common things” set, each student will practice focusing and changing objectives.
Follow steps to focus using low power Using High Power Follow steps to focus using low power Click the nosepiece to High (blue) power Do NOT use the Coarse Focus Knob Use the Fine Focus Knob to bring the slide in focus Only some of the specimen may focus Have students exchange slides so they can look at different things, walk them through using the high power objective to focus slides. Emphasize not using the coarse objective during this process, as it will crack the slides.
Total magnification = eyepiece x objective Eyepiece magnifies 10x 3 different objectives: Scanning (red) 4x total = 40x Low (yellow) 10x total = 100x High (blue) 40x total = 400x
Drawing Specimens Make detailed drawing of exactly what you see! Make sure the specimen is drawn to scale. LABEL what you are observing AND the TOTAL magnification. LABEL any structures to the side and connect to a line.
Example