Re: What is alive?

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From: Burt Kessler (bcomet@postoffice.pacbell.net)
Date: Wed Sep 05 2001 - 17:18:52 PDT 

Date: Wed, 05 Sep 2001 17:18:52 -0700
From: Burt Kessler <bcomet@postoffice.pacbell.net>
Subject: Re: What is alive?
Message-id: <a05010400b7bc6c9b3102@[64.164.11.106]>

>Any great ideas about how to teach - What is life?
>Or Living Vs. Non-living? I am looking for good
>Biology introduction activities. Any and all
>response will be greatly appreciated.
>
I have used an activity where small groups of students are given a
number of objects/materials and asked to classify them as living/dead
or nonliving. They then must come up with a list criteria they used
to make the distinctions. I have given them a test tube of sparkling
water, a pile of dry yeast, a piece of fruit, or leaf or wood, a sea
shell, a rock, a marshmallow, an insect, a nail, a fossil ... . The
discussion about their criteria uncovers many of the characteristics
of life.

I also have lead whole class discussions as a kind of thought
experiment. The scenario is that they are explorers on a new planet
and come across something that looks like nothing they have ever seen
before. The question is "Is it alive? And what will you do to find
out if it is alive?" I have also used this thought experiment with
parents on back to school night with great success. Nearly
everyone's first response is to poke it with something. By directing
the discussion, movement or response to stimuli emerges as a key
characteristic of life. We test each proposed characteristic with
two questions: 1) Can you think of any living things on earth that do
not have this characteristic; 2) Can you think of any nonliving
things that have this characteristic? Most classes, with a little
guidance, can induce all the characteristics of living things. We
also reach the conclusion that to be alive something must have all
the characteristics because many nonliving things have some of them.
Fire is especially life-like. It is useful to revisit this list of
characteristics later in the term when viruses are studied.

Good luck,

Burt Kessler 

-- 
Striving for excellence motivates you;
striving for perfection is demoralizing. - Harriet Braiker

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