Microscopy

Outline of the day 1.Turn in your lab reports at the front –More than 10 minutes late = bad 2.Any questions on last week’s lab? 3.Quiz 4.Introduction to the lab 5.Lab! 6.Check out Get a stamp Make sure I mark you down for attendance

Quiz Ends 8 minutes after it’s started –Ends at: ____

Lab this week! Using the microscope to explore microscopic structures! –Learning how to use a scope Parts of the scope Measuring the diameter of the field –Plants Leaf cells –Seeing chloroplasts, observing the results of osmosis Onion cells –Seeing nuclei (with a stain) –Animals Looking at your own cheek cells –Mitosis Plant cells undergoing mitosis Animal cells undergoing mitosis

Our microscopes Bincocular, compound microscopes –Expensive! Three lenses –4x (low power) ALWAYS start on this lens –10x –40x (high power, used last, if at all) –(The eyepieces have a 10x lens in them as well, so the total magnification is 10x greater than the amount stated on the lens)

Parts of the scope Missing image: Labeled drawing of a scope.

Using the scope 1.Put the scope on the 4x objective 2.Move the stage all the way to the bottom 3.Put the slide on the stage A little clip should hold it in place 4.Using the coarse focus knob, slowly raise the stage until the slide comes into focus 5.Use the fine focus knob to fine-tune the focus, and scroll around on the slide to find the structure(s) you’re looking for 6.If necessary, increase the scope to the 10x objective, and use the fine focus to adjust the focus 7.If necessary, increase the magnification to the 40x objective, using ONLY the fine focus to adjust the focus If the slide is in focus on the 10x objective, it should be in focus on the 40x. 8.Remove the slide, put scope on 4x objective, and move the stage to the bottom

Using a microscope A few key points –You can run the stage into the lens; this is bad (you can break both the slide and the lens) –Always start out on the lowest power possible, get the item in focus there, and then slowly increase magnification

First thing to do: look at a ruler Measure the width of the field of view for each lens CC licensed image: Examples

Elodea leaf This is approximately what you should see: Once you’ve seen that, put some salt-water onto the slide, and observe the change CC licensed images from:

Onion cell Should look something like this: Nucleus is the large purple circle –Nucleolus is the small dark circle inside this CC licensed image:

Onion mitosis You’re looking at a growing onion root tip Find a cell in each stage of the cell cycle –Most cells are in interphase –A few of the cells are undergoing mitosis CC licensed image:

Animal mitosis You’re looking at a growing fish embryo Find a cell in each stage of the cell cycle –Most cells are in interphase –A few of the cells are undergoing mitosis CC licensed images from:

Key points Take your time using the scope –Be careful not to break anything! –Always start on the 4x objective! When you put the scopes away –Turn the light intensity all the way down, then turn it off –Wrap the cord around the base –Be sure there are no slides on the stage –Put the scope on the lowest objective –Lower the stage all the way down –Cover the scope with its plastic cover

Microscopes! Each table has its own set of slides You’ll need to find the structures on the slides –Use your lab manual to figure out what you should look at. Microscopes are in the cabinet in the back When you put the scopes away –Turn the light intensity all the way down, then turn it off –Wrap the cord around the base –Be sure there are no slides on the stage –Put the scope on the lowest objective –Cover the scope with its plastic cover

Before you leave Clean up your work area –Turn in your slide set (show me that they’re all there) –Store your microscope Turn the light intensity all the way down, then turn it off Wrap the cord around the base Be sure there are no slides on the stage Put the scope on the lowest objective Cover the scope with its plastic cover Show me your lab report so I can stamp it –Need to have all data fields filled in –Complete at home and then turn in at the beginning of next lab Remember that we’ll have a quiz at the beginning of the next class –6-7 questions on today’s lab –3-4 questions on the lab we’ll do next week

Notes for the instructor: As these students are beginners at using a scope, I show examples of all the structures during the introduction. My goal here is to help them know what they should be seeing. However, as I don’t want students just copying what I’ve shown (the point is for them to learn to use the scope and see the structures for themselves), I _never_ go back to show those slides again, even if asked. Instead, I help the students find the structures on their own. Telling the students that this is your policy up front will likely help. I hand out a copy of the “using the scope” slide to each group before going over it in class; that way they can keep it while using the scopes.

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History August 2007: Marc Perkins released first version. (If you modify these slides and redistribute them, add your information to the list)