Biology

Cells, Tissues, Organs, Systems

Plants and Animals

1663: Robert Hooke discovers ‘cells’ in corks

How Big Is A Cell?

Unit Length Unit

millimeter (mm) 0.1 cm millimeter (mm)

micrometer (um) 0.0001 cm micrometer (um)

nanometer (nm) 0.0000001 cm nanometer (nm)

Microscopy: An overview

But first a little history!• About 1590, two Dutch spectacle makers,

Zaccharias Janssen and his son Hans, while experimenting with several lenses in a tube, discovered that nearby objects appeared greatly enlarged. That was the forerunner of the compound microscope and of the telescope. In 1609, Galileo, father of modern physics and astronomy, heard of these early experiments, worked out the principles of lenses, and made a much better instrument with a focusing device.

The anatomy of the microscope

Functions of the microscope• What is the function of the following items:

– Objective lenses• To adjust the magnification of the image seen, while keeping the image in

focus.

– Coarse Adjustment Knob• It allows you to move the stage up and down to put the image you see into

focus

– Fine Adjustment Knob• This is used after you have the image in focus through the course

adjustment knob, to allow the image to become clearer (it moves the stage with less sensitivity)

– Stage Clips• Allows for the slide to be held in place

Functions of the microscope

• Revolving nosepiece– Holds the objective lenses and allows for rotation from one lens to

another

• Diaphragm– A diaphragm is a simple device between the light and the slide that

controls the amount of light that passes through the object being viewed

How to calculate magnification

• The ocular lens usually has a magnification on it’s own of about 10x

• The objective lenses can range considerably but usually are 4x, 10x, and 40x

• To calculate the total magnification you multiply the ocular lens magnification by the objective lens magnification you use–So if your medium is 10x then your total

magnification will be

10 X 10 = 100x

Drawing what you see!• All drawings should include

clear and proper labels (and be large enough to view details). Drawings should be labeled with the specimen name and magnification.

• Labels should be written on the outside of the circle. The circle indicates the viewing field as seen through the eyepiece, specimens should be drawn to scale - ie..if your specimen takes up the whole viewing field, make sure your drawing reflects that.

Drawing what you see!

• When you are completing biological drawings in class please ensure that the following are adhered to:– The page is clean and neat– The circle for the field of view is in pen and is

created using a compass or a round object.– The image is drawn to scale.– The image is drawn in pencil.

Drawing what you see!• When filling an image in, stippling not shading is

used.• All labels are to the right side and a ruler is used to

create lines.• Magnification is placed in the lower right corner of

the drawing.• The title is specific and underlined, in pen.• The entire image has been duplicated, not just part

of it.• The image is complete and drawn to the best of your

ability.