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Living or Nonliving?

Kathryn M.Hopkins

This lesson is a constructivist lab activity which follows class work done on the features and needs of living things, and cooperative group activities to determine whether things are living or nonliving. It has been used with seventh grade life science classes and high school biology classes.

Students receive a letter from the "National Space Agency" asking for their help in testing some samples which have recently been brought back from space. Students are asked to devise a series of tests which they will then perform on the samples to determine whether they are living or nonliving.

The letter contains some broad hints about what tests might be effective - these, of course, are based on the students' previous experiences and things with which they are familiar.

Each of the cooperative groups brainstorms, comes to consensus on what should be done, writes a draft experimental design procedure and submits it along with a list of needed materials. The teacher returns the drafts with suggestions and the requested materials. The groups make task lists and timetables, assign roles and get to work.

The teacher needs to make sure she has time to collect and assemble the materials; the lab requires a lot of containers and a fairly organized method of storing the students' "stuff". The samples given to the groups are: radish seeds, brownulated sugar, brine shrimp eggs, yeast, sand and freeze-dried brine shrimp (the fish food kind - they're cheap). Live brine shrimp are fun to add as another sample, if they are available - you can get them at aquarium stores. The class will need microscopes, some kind of food (students usually decide that sugar water is the best thing, but others go for fish food or other critter food found in the classroom), water, pipettes, indicators for carbon dioxide, measuring containers, slides and both dark and light places to store things which might grow.

The lab usually takes 3 days or more. The members of each group write individual reports as well as a group report to present to the class. These group reports are videotaped and each class member prepares a peer review sheet for each of the other students.

The individual lab reports contain materials used, procedures, data tables and graphs, descriptions of successes and failures, suggestions for future work and final conclusions. These are graded, returned and placed in portfolios.

When we do portfolio reviews, students almost always choose these reports as examples of their best/favorite work. Their reasons usually center on the fact that it was really hard to figure out what to do, but that the method was invented by the students and it felt great to be successful with such a difficult task.

It is very important for the teacher to answer questions and nudge the students in the right direction - many tend to go off on a tangent which will get them nowhere and the teacher must ask "why are you doing that?" "what do you think will happen?" "do you think you might...?" kinds of questions. Of course, some will not take even the broadest of hints or the heaviest-handed of suggestions, but they usually learn from their mistakes.

This lab activity is a delight for the teacher (after she gets the materials together and corrects the drafts). The students do amazing, goofy, weird and wonderful things - including naming the critters Ralph and shouting "Yo Ralph" at them on the slide to see if they respond. And they always come away from the experience with a clear understanding of the differences among living, nonliving and dead things.

Sample Letter _______________________________________________________
(A graphic related to space is nice in the heading)
National Space Agency
101 Satellite Ave.N.W.
Washington D.C. 20002

(Address of your own students)

Dear Students,

It has come to my attention that you are science students who have completed an extensive study of the features and needs of living things, and can conduct some experiments relating to materials which might be living or nonliving. I understand that you are able to determine carbon dioxide production, make cell population counts,
measure growth, observe respiration rates and so forth.

In my position as director of the agency, I have been authorized to ask for your help with a most pressing matter. We have recently received samples from space and must determine if they are living or nonliving. We would be most appreciative if you would, in your cooperative lab groups, perform tests to make this determination. We will expect you to write draft experimental designs and submit them to your teacher for approval and to request the necessary materials from her. We will remain in contact with your teacher and she will convey our further directions to you.

In anticipation of your helping us with this most important task, we have forwarded the samples to your school. We look forward to your reports of your success and thank you for your help.
Sincerely yours,

Alfred P. Aerosmith, Director

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