Micro-organisms

Janet Elkins                   F. A. Douglass Middle Math & Science Academy
                               543 N. Waller
                               Chicago IL 60644
                               (312) 534-6176 
 
Objectives:

     This lesson has been developed for 6th grade students, but is easily 
adaptable to other levels.
     Students will:

          -assemble a wet-mount slide
          -demonstrate the use of a microscope, focussed on the specimen
          -demonstrate the mastery of observation
          -utilize vocabulary of mold structural parts in journal and/or 
           presentation/questioning by Teacher
          
Materials Needed:

     Paper towel or paper napkin
     Clean, blank slide(s)
     Slide cover(s)
     Water
     Mold from piece of bread
     Forceps
     Microscope

Strategy:

     In preparation for this lesson, students/teacher will already have prepared 
some bread mold.  I usually wipe the classroom floor (if uncarpeted), a chalk 
ledge, or window sill with half a slice of home-made bread.  I lightly spray it 
with water, and then EITHER place in a sealed baggie, OR lay on a saucer in an 
out-of-the-way place.  If you use the saucer method, you may need to re-moisten 
the bread every day or two. 
     Once the mold has started to grow (2-3 days), you may want to allow it to 
dry out, so that student(s) or you who are sensitive to molds will be less so.  
I ALWAYS CAUTION against touching or breathing the molds.

Part A     (I usually give the directions for making a wet-mount 3 times; tell, 
show, tell.  My directions differ from our science text.)  Place a clean slide 
on top of a paper towel or piece of paper.  Place 1 or 2 drops of water on it.  
(Use the tip of your finger, or use a dropper.)  With the forceps, take a TINY 
pinch from the bread mold and MASH around into the water.  (Tiny because we are 
using a microscope, and just a bit will look big; the mold structures are 
sturdy, and will not be harmed.  Having them spread out will allow the light of 
the microscope to shine through it so the structures can be easily seen.)  
Holding the slide cover by the sides between forefinger and thumb, slide 1 edge 
TO THE EDGE of the water droplet, and then DROP the cover on to the slide.  (If 
there are any air bubbles, they will show up as silver shapes, but should not be 
a problem.) 


Part B    Secure the slide on the platform with the slide clips.  (Holds the 
slide steady for viewing.)  Make sure that some of the mold is over the light 
which is coming in via the mirror or lamp.  Then with the lowest-powered lens 
(usually the shortest) in place, focus by slowly turning with the coarse 
adjuster until you see something; then adjust the fine knob until the "picture" 
is clear.  DRAW what you see in the journal, or on the observation sheet.  LABEL 
the ball-like top "sporangium", and the stem AND root-looking parts "hyphae". 
COMPARE it with your team members. 

Performance Assessment:
      
A.  Can prepare a wet-mount slide, using material from the experiment 
                         slide cover atop slide specimen             1

                         slide cover indicates air bubbles-some      1
                                                          -few       2

B.  Can put a slide on the microscope platform

                         light shining on specimen in lens           1

                         specimen focussed-somewhat                  1
                                          -sharply                   2


C.  Can label/name       -microscope parts (max. based on YOUR microscope)
                                 1 pt. per part                      0-6
                         -mold parts                                 1-2
                         -did drawing                                1
                         -labeled drawing                            1
                         -1 pt. per part labeled                     1-3

PASS = 11 pts. or more; FAIL = 10 pts. or less.