[nabs-l] Microscope Lab Coming Up

[Tina Hansen]

In one of my courses, I have a lab that will involve use of the microscope. I'm concerned about this, since everyone will need to view slides and/or prepare specimens. To give you a bit of an idea of what's coming up, I've copied the procedure and background information into this message.

Bi 131 Environmental Science

Symbiosis Laboratory

 

The populations of all living species occurring in a given area define the community.  Animals, plants, fungi, protists and bacteria are all included in this assemblage.  In addition to sharing a common piece of turf, the members of a community are also tied together by often complex interrelationships.  Symbiosis is an example of one of these relationships.

 

The term symbiosis is used to describe an ecological relationship between organisms of two different species that live in very close association with one another.  The smaller participant in the relationship is called the symbiont and the larger participant, the host.  Different types of symbiotic relationships are described based on which member benefits or is harmed by the relationship.  In mutualism, both members gain some benefit from the relationship.  In parasitism, only one member (the parasite) benefits (usually the smaller) at the host's expense.  If there is no clear harm or benefit to the host the relationship is commensalism.

 

In today's laboratory we will examine a number of examples of symbiotic relationships.  

 

PROCEDURE:

 

Examine the various examples of symbiosis available in the laboratory as described below.

 

1.         Paramecium bursaria - Make a wet mount from the Paramecium culture and view at 100X and 450X.  Note the symbiotic green algae (Zoochlorella) inside the membrane of Paramecium.

 

2.         Lichens - make wet mounts of various lichens after grinding up lichen tissues in a small amount of water with a mortar and pestle.  View slide at 100X and 450X and note the filamentous brown and colorless tissue (=fungus) and the symbiotic single-celled algae.

These algae will appear as small green spheres.

 

3.         Termites - remove termite gut as demonstrated and place contents on a microscope slide containing several drops of 0.6% saline.  Pick the tissue apart with probes and prepare a wet mount.  View at 100X and 450X and observe symbiotic protozoans (Trichonympha) and possibly, bacteria.

 

4.         Azolla (a floating fern) - make wet mounts of Azolla after grinding up tissues with a mortar and pestle.  View at 100X and 450X.  The larger, light green cells are those of Azolla and the darker, blue-green chains of cells are Anabaena, a symbiotic, nitrogen-fixing blue-green algae.

 

 

 



5.         Scale insect on pine needle - while viewing under a dissecting microscope gently lift the small, white, teardrop-shaped scale with a fine probe and observe the tiny symbiotic scale insect underneath.

 

6.         Oak galls - gently break open a gall with your hands or a pair of scissors to expose the central "core" of the gall.  Carefully cut open the central core with a razor blade or scalpel and observe the larva under a dissecting microscope.  Adult wasps that have emerged from galls may also be available for observation.  They are very small and do not sting.

 

7.         Mossy rose galls - cut open gall with scissors or scalpel.  Observe larva under dissecting microscope.

 

8.         Hydra - see demonstration under dissecting microscope on rear lab table.  Note symbiotic green algae (Zoochlorella) within the tissues of Hydra.

 

 

 

Please note:

 

Specimens #1, 2, 3, and 4 require the preparation of a microscope slide and observation using a compound microscope.  Specimens #5, 6, 7 and 8 may be viewed directly using a dissecting microscope and do not require the preparation of a slide.

 

Enter information for each symbiotic relationship on the charts on the following pages.  Fully describe the nature of the benefit or harm brought to each member of the relationship under "Description of Symbiotic Relationship".  For example, the dog-flea relationship might be described as follows:

 

"The flea benefits from the relationship by gaining nutrients and a habitat from the dog, which is harmed by losing blood, being irritated and possibly contracting a disease from     the flea."

 

On pages 3 and 4 of this handout, make detailed drawings of the host and symbiont for each relationship.  Be sure to label each drawing completely - include an overall title, names of each of the symbionts and the names of any structures that can be seen.



Does anyone out there have suggestions for dealing with labs like this? Thanks.