Lab Shedule
Lab 01
Lab 02
Lab 03
Lab 04
Lab 05
Lab 06
Lab 07

Cell cycle game

BIO 196 Official Website

Microscopy Results

The microscope is one of the most important tools in the field of Biology. Because of this, it is critical that students learn to grasp the basic concepts behind its use and management. While this lab does not consist of any experimentation, there are several key points that should be understood.

Exercise A

The parts of the microscope are initially discussed on pages 2 & 3. The diagram of the objective on page 3 illustrates the labelling system that is common on a microscope you may find in the lab. Arguably the most important digits are the magnification and numerical aperature (NA) . The numerical aperature determines the resolving power of the objective. The two equations mentioned in the book help to explain this idea.

It's important when analyzing the forumulas to remember that a smaller R is better. When you increase the numerical aperature, the fraction in the equation becomes smaller and hence R is smaller (because R is equal to this fraction). Increased magnification without increased resolving power is pointless because you will not be able to observe greater detail in your specimen. Try this in the real world by looking at a photograph up close - you cannot discern any greater details because you are limited to the resolution with which the picture was taken. One more thing to note - the n value in the first equation is the refractive index of the medium through which light is travelling. The value for air is simply "1".

Exercise B

Important concepts for this exercise:

• Total magnification = ocular magnification * objective magnification
• As magnification increases, field of view decreases
• The letter e should appear both upside down and backwards

Exercise C

It may have been difficult to observe cyclosis in the leaf specimen but you should have seen organelles moving around in a circular fashion. When the salt solution replaces the regular water, cyclosis should slow down and eventually stop because most of the water leaves the Elodea leaf.

Exercise D

This section of the lab involved measuring objects under the microscope and observing differences in the field of view at various magnifications. The first equation allows us to measure the area under the field of view once at a particular magnification and apply that knowledge to solve for other objectives. In the following example, a ruler is used to measure the distance under the 4x objective (total magnification = 40) and then the equation solves for the 100x magnification. Again, it's important to note that with this equation you don't actually have to change the objective to 10x, 40x, 100x, etc. You only need to keep the 40x and 5000 micrometer values while plugging in other numbers.

The final part of this exercise required the use of the ocular micrometer to measure objects under the microscope. However, before this could be accomplished, the ocular micrometer needed to be calibrated. We used either a ruler or a stage scale to calibrate the ocular micrometer at a particular resolution. The following diagram demonstrates this process.

Exercise E

This final part of the lab introduced the disecting microscope. All of the required parts are listed in earlier pages of the laboratory manual.

That's about all for this week. If you have any questions feel free to get in touch with your laboratory TA and he or she will be more than happy to help.