Warm-up on page 14

• Which types of cells lack a nucleus? Prokaryotes or Eukaryotes– Prokaryotes

• Which cells have membrane bound organelles?– Eukaryotes

• What type of microscope do we have in lab?– Compound light microscope

As magnification increases, the field of view decreases!

• At 40x magnification you will be able to see 5mm.

• At 100x magnification you will be able to see 2mm.

• At 400x magnification you will be able to see 0.45mm, or 450 microns.

• At 1000x magnification you will be able to see 0.180mm, or 180 microns.

1X Low power – 10X

Medium power – 25X High power – 43X

Because specimens are three dimensional, and vary in thickness, you must make

adjustments as you view the specimen. This is especially true if you are looking a

live organisms that are moving.

The magnification of an object is calculated by multiplying the magnification of the eyepiece lens (10X) by the magnification of the objective lens. Ex) 10X x 43X = 430X

10X

20X

40X

Using A Microscope

1. Start on the low objective lens with the stage lowered and the specimen placed on the stage.

2. Adjust the course adjustment knob until you can see the image.

3. Use the fine adjustment knob to focus clearly on the specimen.

4. Rotate the nosepiece to high power. Do not move the stage!

5. Use only the fine adjustment knob to bring the specimen into focus!

Escherica coli (bacterium)

1000X .5 - .8 um

Human Red Blood Cell

1000X 6 - 8 um

Human Egg Cell

1000X 100 um

Saccharomyces cerevisiae(Yeast)

1000X 5 - 10 um

Streptococcus pneumoniae(Bacterium)

1000X .5 – 1.3 um