Biology Unit C: Cycling of Matter in Living Systems Chapter 1: Developments in Imaging Technology

A Window to a New World Agenda: Introduction to Microscopes Uses for Microscopes People involved in Scientific Discovery and Inventions/Improvements to Microscopes: Aristotle Hans & Zacharias Jensen Robert Hooke Antoni van Leeuwenhoek Types of Microscopes Parts of the Compound Light Microscope Care and Use of the Microscope

Microscopes What do we use Microscopes for? Non-traditional uses: To see anything that is difficult to see with the naked eye (plant parts, animal parts) http://en.wikipedia.org/wiki/Microscope Non-traditional uses: Solving crimes: (hair analysis, blood, other fluids) Detecting crop diseases and pathogens Detecting tiny defects in metal in bridges and airplanes Detection of diseases like malaria and Tuberculosis Use in Surgery (laparoscopic)

A Brief History So how did we come to use Microscopes? It began with Scientific Inquiry – Asking questions about how things work Early Greeks Mostly philosophers – thinking out possible answers to problems rather than testing ideas Aristotle (384 to 322 B.C.): Followed a pathway of accurate observations and record making Set up a classification system based on his observations Reasoning and Interpretation followed the observations

A Brief History Hans and Zacharias Janssen Holland, ~1595 Father and son Dutch lens makers Invented the compound microscope (2 lens system) Magnifying power ~ 20 X http://en.wikipedia.org/wiki/File:Zacharias.jpg

A Brief History Robert Hooke (1635-1703) Used a hand made microscope with a 3-lens system Recorded observations of plants, animals, and non-living objects Viewed cork and saw many empty channels, which he called “cells” because they looked like Monks’ cells http://en.wikipedia.org/wiki/Robert_Hooke Light was concentrated on the subject by passing it through a water-filled glass flask. Early proponent of “biological evolution” due to his close observations of fossils. http://en.wikipedia.org/wiki/File:HookeFlea01.jpg http://en.wikipedia.org/wiki/File:Hooke_Microscope-03000276-FIG-4.jpg

A Brief History Antoni van Leeuwenhoek (~1665) Identified different types of single celled organisms such as bacteria, sperm and unicellular protozoa Highly skilled in making small lenses, and was able to produce higher magnifications than the compound microscopes of the day A Replica of van Leeuwenhoek’s Microscope http://en.wikipedia.org/wiki/File:Leeuwenhoek_Microscope.png Dutch business man who used a single lens microscope to see the movement of the different types of single cells. Microscopic section through 1 year old Ash tree wood http://en.wikipedia.org/wiki/File:Leeuwenhoek_Eschenholz.jpg

Equivalent Measurement Microscopes Units of Measurement Unit Equivalent Measurement Useful in Observing Centimetre (cm) 1/100 metre; 10-2 m Visible objects Millimetre (mm) 1/10 centimetre; 10-3 m Large particles or cells Micrometre – also known as the Micron (µm) 1/1000 millimetre; 10-6 m Majority of cells and their component parts Nanometre (nm) 1/1000 micrometre, 10-9m Large molecules and most cell parts Angstrom (Å) 1/10 nanometre; 10-10m Molecules and atoms Now they have powerful enough microscopes to see strands of DNA or even individual atoms!

Microscopes Types of Microscopes 4 basic types of microscopes (in two categories): Light Microscopes: Dissection microscopes Compound Microscopes Electron Microscopes: Scanning Electron Microscope Transmission Electron Microscope

Light Microscopes Use light focused on the object to illuminate it A thumb through a dissecting microscope Use light focused on the object to illuminate it Dissection microscope: Image is 3-D, but it only has a low magnification, so you cannot see individual cells Compound microscope: Image is 2-D, but the magnification is powerful enough to see individual cells (with a low resolution) http://www.itg.uiuc.edu/exhibits/gallery/pages/image-26.htm Human hair at 100x mag. http://www.microscopeworld.com/MSWorld/microscope_images.aspx Human hair at 400x mag. http://www.microscopeworld.com/MSWorld/microscope_images.aspx

Electron Microscopes Use a beam of electrons, rather than light, to illuminate the object you are viewing Scanning Electron microscope (SEM): High magnification and high resolution, image is 3-D Objects are coated in gold then the electrons bounce off the outside to give you a black and white image Transmission Electron microscope (TEM): Electron beams pass through thin specimens of the object, giving a 2-D image with high resolution at a high magnification http://www.arco-iris.com/George/microscopes/micro_fossil_02.jpg Synapse from a rat’s visual cortex http://www.itg.uiuc.edu/exhibits/gallery/pages/image-51.htm

Compound Microscope You will be using a compound microscope for your lab You will need to know the different parts of the microscope and how to use it safely and carefully http://www.yorkoptical.com.au/portals/0/StockImages/14001-049-I01.jpg

Compound Microscope Revolving nosepiece Body tube Arm Objective lenses Ocular lens (eyepiece) Revolving nosepiece Body tube Arm Objective lenses Course adjustment knob Stage Fine adjustment knob appears below the course adjustment knob on your diagram in your notes The iris diaphragm is right underneath the stage on your diagram Stage clips Power switch Base Light source Note: Fine adjustment knob and iris diaphragm do not appear on this diagram http://www.yorkoptical.com.au/portals/0/StockImages/14001-049-I01.jpg

Parts of the Microscope Eyepiece or Ocular Lens: Has a lens that enlarges the image from the objective lens (usually 10X) Course Adjustment Knob: Brings the image into focus. Used only with the low power objective lens Fine Adjustment Knob: Brings the image into focus with more detail Used with the medium and high power objective lenses Arm: Supports the microscope Use to help carry the microscope

Parts of the Microscope Revolving Nosepiece: Rotating mount that holds many objective lenses Objective lenses: Gathers light from a specimen and forms an inverted image Low = 4X magnification Medium = 10X magnification High = 40X magnification Stage: Supports the microscope slide Stage clips: Holds the slide in place http://www.fotosearch.com/photos-images/microscope_2.html

Parts of the Microscope Iris Diaphragm: Controls the amount of light reaching the object Light Source: Sends light up through the object being viewed Also called “lamp” or “mirror” Base: Supports the microscope Also hold this when carrying the microscope (along with arm) Power Switch: Turns the light source on/off May or may not be present on all microscopes

Care and Use (p. 5) Read the information before you start http://www.fotosearch.com/photos-images/microscope.html Read the information before you start Practice the skills you learn Ask questions if you are not sure! 1. Always use 2 hands to carry the microscope! In the upright position with one hand supporting the base, and one holding the arm 2. Do not touch the lens with anything 3. Always check that the light switch is OFF before you plug it in 4. Always store your microscope with the stage lowered and the revolving nosepiece at its lowest point 5. Cover the microscope and return it to its storage place 6. YOU are responsible for cleaning your equipment (including the glass slides) after use. Use only lens paper to clean lenses. 7. Inform your teacher if your microscope does not work

Viewing Objects with the Microscope (p. 5) 1. Check that the stage is at its lowest point and turn the objective lens to the lowest power 2. Secure a prepared slide on the stage 3. While watching the stage raise it until the slide gets as close to the objective lens as it can without touching it 4. Look in the ocular lens while you use the course focus to LOWER the stage until the object comes into view. Fine focus is used to get a sharper image. Adjust the iris diaphragm if necessary 5. Turn to the medium power lens. Only use the fine focus adjustment under medium and high powered lenses! 6. Lower the stage and return the objective lens to the lowest power before removing the slide http://www.fotosearch.com/photos-images/microscope.html

A Look Ahead Next Class: You will be using a microscope in pairs in the laboratory for class. Bring your microscope handout, a pencil, and a ruler. It’s also not a bad idea to bring your C1 booklet with the care and use instructions as well as the list of the parts of the microscopes