Microorganisms play an important part in our lives. As decomposers of organic material, they help keep the soil fertile, and recycle once-living matter into valuable nutrients for plants. Microorganisms in food production, and microorganisms as primary causes of food spoilage are some of the things students could consider while they observe, describe, and identify microorganisms which they culture in their classroom.
The use of microscopes, previously suggested in units of grades 4 and 6, is a necessity. Students should have an opportunity to acquire some skill with the microscope, and appreciate the diversity of lifeforms in the microscopic world.
It is difficult for students learning to use a microscope to know whether what is in the field of view is significant or not. High quality microscopes help alleviate this challenge. One $750 microscope, used in rotation by five groups, may be a better value than five $150 microscopes. A television camera adapter for a microscope, so that a group of students can watch the screen, may be a good solution. Viewing videotapes or films which show active microorganisms may give students an idea of what to look for and how to recognize what they see. It is important to make this contact with the study of microorganisms and the use of microscopes as frustration-free as possible.
When doing any activities with microorganisms, it is best to treat them all as if they were human pathogens. While it is fairly safe to use student-prepared microscope slides to examine protozoans and algae from pond water or from hay infusions, the examination of bacteria should be restricted to unaided viewing, or using a hand lens or stereomicroscope to view cultures grown in sealed petri dishes. Commercially-prepared slides may also be used.
This unit offers the opportunity for integration with the core unit Life: Keys to Survival. Together, they offer a good background for the environment units in grades 8 and 9.
Science writing and reading activities, as discussed in this Guide, should be incorporated into each lesson. Reading from newspapers, texts, and journals broadens students' input from what can be experienced in the classroom or in their day-to-day lives. Reporting on the activities of science class through learning logs, writing newspaper editorials expressing informed opinions, and writing scripts for video newscasts are three strategies through which students may refine their understanding of the concepts of science and develop their ability to communicate through the written word.
Science challenge, as described in this Guide, is meant to extend students' critical and creative thinking abilities in the context of the science concepts being studied. The challenge is intended to give each student a chance to investigate an area of interest in more depth than would be possible for all students in a class to do. Science challenge is a key strategy for bringing the Adaptive Dimension to the classroom, and for encouraging independent learning. A class booklet describing various bacterial and viral infectious diseases, with each group contributing a chapter, is an example of a cooperative science challenge activity that results in a product usable in the students' own classroom.
.
.
To collect pond or dugout water, obtain a 2 or 3 metre length of 10 mm to 20 mm inside diameter plastic tubing. Holding your finger tightly over one end of the tube, introduce the other end into the pond. When you have manipulated the tube to where you want to take the sample, remove your finger from the end of the tube and the water should flow in. Replace your finger over the end, withdraw the tube from the pond and release the captured water into an ice cream pail or other container by removing your finger.
A hay infusion can be used to produce a protozoan culture. Add a small handful of hay or dried grasses to about 500 mL of water. Boil for about 10 minutes and then distribute the water and materials to culture jars. Wheat (20-30 kernels) may be added to provide additional nutrients for the microorganisms. The water should be distilled water, well water, pond or river water, or from some other source that has not been treated.
Paramecia and other protozoans move fairly quickly across a 100x field of view. A drop of methyl cellulose solution or polyvinyl alcohol solution added to the drop of culture when preparing the wet-mount slide slows the movement of these organisms, making them easier to observe. Consult a high school biology lab manual for tips on producing wet-mount slides of protozoans.
If you have access to a video camera and can adapt it to take pictures through a microscope, a video clip of paramecia on a TV monitor can be very useful in helping first time microscope users to identify protozoans, algae and air bubbles. This can save students a lot of frustration and requests for assistance.
Factors: B4, B18, C1, E1, E7, F1, G1
Objectives: 1.1, 1.2, 1.4, 1.5, 5.1, 6.3
Assessment Techniques: performance assessments, self assessments, observation checklists
Instructional Methods: guides for viewing, inquiry, assigned questions, discussion
Factors: A9, B2, C15, D3, G3, G5
Objectives: 3.5, 4.1, 4.2, 5.3, 5.5
Assessment Techniques: presentations, short answer test items, written assignments
Instructional Methods: case studies, research project, cooperative learning groups
Objectives: 1.1, 1.3, 4.1, 6.1
Assessment Techniques: anecdotal records, presentations, self and
peer assessment
Instructional Methods: inquiry, conducting experiments, laboratory
groups
Sketch the mushrooms and describe their colour, odour, surface characteristics,
and structure. Cut the stem as close as possible to the cap. Lay the cap
gill side down on two pieces of paper (one white, one black) arranged so
that half the cap is over the white sheet and half over the black sheet.
In two to three hours, enough spores should be released from the gills to
produce a spore print on the paper. Invert a beaker or a jar over the cap
while the spores are being deposited. This prevents air currents from disturbing
the pattern. When the print is complete, it can be preserved by spraying
with hair spray.
Spore prints are used in identifying the species of mushroom since the
colour of the spores is an important characteristic property.
Note: Many of the resources listed in Science: An Information Bulletin for the Middle Level - Key Resource Correlations describe activities or ideas for activities.