Microscopes & Cell theory

Microscope development:• Hans and Zacharis Janssen:

1590 –simple microscope; 2 lens in a tube

• Anton van Leeuwenhoek: early 1660’s- used microscope to observe nature & recorded it.

Describe the properties of microscopes.

• Microscope: magnifies images

• Magnification: increase in size

• Resolution: increase in detail

• Two types:• Light microscopes • Electron microscopes

Light Microscopes• Magnifies objects using

light• Simple microscopes:

have only one lens (magnifying glass)

• Compound light microscope: has two lenses

Using the microscope:• Find total magnification: multiply power of eyepiece

(usually 10X) x power of objective lens• When focusing: always start with LOW POWER

objective• Move nosepiece all the way down and focus slowly

UPWARD using the coarse adjustment

Electron Microscopes• 1940’s, uses electron beams

instead of light• Allows more detail, but

specimens are usually killed in the staining process

• Two types:• TEM: beam goes through

specimen• SEM: scans surface only

Parts of a microscope• Ocular lens: lens near eye • Eyepiece: holds ocular lens• Objective lens: lens near specimen a. high power lens: longer, usually 40 X b. low power lens: shorter, usually 10 X• Nosepiece: holds objective lenses• Stage: platform supporting specimen• Diaphragm: regulates amount of light • Fine adjustment/coarse adjustment: used to focus on object• Arm: supports microscope• Illuminator: light source

Robert Hooke discovered cells in 1665

a.Examined a wine cork(tree)

b.looked like his monastery cell so he named them “cells”

How did the Cell Theory come about?

• Schleiden and Schwann (1838-1839) examined many types of cells

• Schleiden: botanist, discovered that all plant parts are made of cells

• Schwann: zoologist, discovered that all animals parts are made up of cells

• Both observed / different types of cells performed different functions

Schwann 

Schleiden

• Rudolph Virchow (1855)• Physician that stated all

living cells come only from other living cells

The Cell Theory

• All organisms are made up of cells

• Cell is the basic unit of organization

• Cells come from pre-existing cells

Stem Cell Research

http://www.sumanasinc.com/webcontent/anisamples/stemcells.html

Website-stem cell animation