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Tenebrio molitor

By Judith Averbeck, S.N.D.



Type of Entry:

  • Project

Type of Activity:

  • Hands-on activity
  • Inquiry lab
  • Group/cooperative learning

Target Audience:

  • Advanced/AP Biology
  • Gifted

Background Information

Notes for teacher:
This activity was devised in response to the overwhelming amount of material stipulated for the Advanced Placement Biology course. It allows for some of the content to be covered by students working independently outside of class time.

Required of students:
Students must have knowledge of general lab procedures, be highly motivated and capable of responsible behavior.

Students select two or three partners with whom to work. The group of three or four is then required to carry out a unique laboratory activity once each quarter. (This is in addition to regular lab exercises done in class). The work is done completely outside of class time. Students must organize their time, plan the procedure, meet to gather data, research the topic, and write up an extensive report that is due the last day of the quarter at 9:00 PM.

Preparation time needed:
The teacher must be willing to put in a lot of preparation time organizing the content initially and in assessing the resulting "lab reports" quarterly. Time spent overseeing the actual experimentation is minimal.

Class time needed:
Other than introducing the concept of Open Lab and explaining the type of report expected, no class time is required.


Abstract of Activity

Open Labs are investigations carried out once each quarter by cooperative groups of 3-4 students. They are designed for AP Biology classes in an attempt to cover outside of class time some of the extensive content required in the course. They involve "doing science," allowing students to be somewhat creative in designing and organizing parts of their experimentation. Cooperative learning is fostered since it is almost impossible for one person to do all the work, and a joint lab report is submitted.

The actual topics of the investigations vary somewhat from year to year, but typical ones are: Effect of X-radiation on Radish Seeds, Response of Tenebrio to Environmental Stimuli, Population Ecology and Factors Affecting the Rate of Photosynthesis. I created the first two labs, basing them on interest and availability of equipment. Population Ecology (part of the Explorer series published by Logal) is a computer simulation of factors affecting natural population growth. The Photosynthesis lab is a modification of the AP version, with a few added sections and options for students to pursue.

For the first lab, I provide a somewhat detailed procedure for the students to follow. As the quarters go on, I provide less and less for the students in the way of procedure or hints on data organization. They begin to provide their own references. There is always a section that students must be "creative" in. For example, they may have choice of a variable to test or of which organism to use. They also may do optional parts if they so choose. By the end, students are pretty independent in doing their science. In addition, I find that the content of the lab work is retained for a much longer period than similar content from a textbook would be.


Lesson/activity

Materials needed:
Directions for four extensive lab experiments that can be safely performed using equipment available in your laboratory. The first directions are rather detailed and explicit. The second less so, etc. In addition, a direction sheet detailing the type of report required.

If you choose to use Population Ecology, it is available from Logal Software Inc., Cambridge, MA. 1-800-LOGAL-USA Fax: 617-491-5855

Advanced Placement Labs are available from: Advanced Placement Program, Dept. E-22, P.O. Box 6670, Princeton, NJ 08541


Activity

This is a sample of one of the "home-made" Open Labs used this year. This is the direction sheet given to the students. It was second in the sequence and therefore moderately detailed.

OPEN LAB TENEBRIO

The purpose of this lab will be to study the influence of various environmental factors on the behavior of the insect, Tenebrio molitor.

Plastic tubes with removable ends will be used as the experimental chambers. The basic procedure consists of placing contrasting conditions at either end of the tube with at least six organisms in the middle. After about 30 minutes have elapsed, the number of organisms "choosing" each condition is counted. This is repeated at least 5 times to produce a "run" of thirty trials.

The chi-square test is used to determine whether the data indicates a real preference of the insects for one condition over the other, or reflects merely random deviation from the expected. Be sure to consider carefully what the expected value for each run is and what a large p-value indicates in this situation.

After each trial, the tubes must be washed thoroughly with soap and water to eliminate any scent trails left by previous occupants.

You will find that overdoing the ingredients at the ends of the tubes leads to inaccurate data. For example, too much water will saturate the tube with humidity and thus, in effect, erase the differences between ends.

Variables you must test on both adult and larval Tenebrio are:

  • Light/Darkness
  • Dryness/Wetness

Variables about which you have choices are:

  • Cornstarch/Potato starch
  • Low pH/High pH
  • Amputation of antennae (if you choose this option, see instructor before beginning)

You must do at least one of the optional variables and test it on both larval and adult beetles.


Method of Evaluation/Assessment

The primary evaluation is the grading of the completed report at the end of each quarter. The real value of this time-consuming task is the abundant feedback given to the students right on their report. The components scored are:

  • Accuracy of data
  • References included
  • Optional parts undertaken
  • Organization of data
  • Correctness of procedure
  • Extensiveness of bibliography
  • Overall neatness
  • Correctness of conclusions
  • Quality of writing
  • Improvement of previous weak points

At the end, I list the strongest points of the work and the weakest. The next quarter, I look especially for improvement in the weak areas. Students are aware of this and concentrate on these areas the next time around.


Extension/Reinforcement/ Additional Ideas

There are many, many topics that could be used in Open Lab format. The number is limited only by the creativity of the teacher and the time required to set up directions and equipment.


ACTIVITY

Students select two or three partners with whom to work. The group of three or four is then required to carry out a unique laboratory activity once a quarter. (This is in addition to regular lab exercises done in class). The work is done completely outside of class time. Students must organize their time, plan the procedure, meet to gather data, research the topic, and write up an extensive report that is due the last day of the quarter at 9:00 PM. The topics vary somewhat from year to year, but typical ones are: Effect of X-radiation on Radish Seeds, Response of Tenebrio to Environmental Stimuli, Population Ecology and Factors Affecting the Rate of Photosynthesis. I created the first two labs, basing them on interest and availability of equipment. Population Ecology (part of the Explorer series published by Logal) is a computer simulation of factors affecting natural population growth. It teaches, in a very interactive format, population concepts impossible to duplicate in a "wet" lab. I modified somewhat the materials provided and added questions to cover some concepts I felt were neglected (like human population growth). The Photosynthesis lab is a modification of the AP version, with a few added sections and options for students to pursue.

For the first lab, I provide a somewhat detailed procedure for the students to follow. I also gather reference books from local libraries and put them in the lab for use. Equipment is placed on a special cart reserved for Open Lab and is available at all times. Since my school is "open" most evenings and weekends, the students have access to the lab. They can also use the school computers for data base searching, word processing, graphing, statistical analysis, etc. The written report contains introduction (with literature citations in standard format), procedure, data, discussion and conclusion sections, and so is quite extensive. I evaluate it thoroughly (a task that takes at least 90 minutes per report), giving abundant feedback. I list factors that I expect to see improvement on next quarter.

As the quarters go on, I provide less and less for the students in the way of procedure or hints on data organization. They begin to provide their own references. There is always a section that students must be "creative" in. For example, they may have choice of a variable to test or of which organism to use. They also may do optional parts if they so choose. By the end, students are pretty independent in doing their science.

I like this series of activities for a number of reasons. First of all, the students are forced to read science outside of a textbook and somewhat understand it. They become intimately acquainted with the method of science and with scientific writing style by doing. They gain freedom from the cookbook approach to lab that is often necessary to use because of time pressure. They gain confidence in their ability as they see their labs improve from quarter to quarter. Being forced to work as a group is often painful for a competitive AP student (all members of a group get the same grade on the lab). Having to cooperate in finding time to come together, to hash out data, to compile the finished product is a life-valuable experience, I believe. It is almost impossible for one person to do all the work, so cooperative learning is imperative. Despite the complaining and groaning, students are usually proud of their finished work once it is finally completed (often at 8:59). And, I find that the content of the lab work is retained for a much longer period than similar content from a textbook would be.


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