Dichotomous Keys, WebQuests and the Zoo–Part 1

We have been busy scientists lately in Rm. 202.  Let me tell you about it! (And also let me apologize for not writing about Science very often.  This may be one of the first posts I’ve ever included about our lives as scientists…boo. 😦 )

During 3rd quarter we were busy learning about many things.  The latest science unit we ventured through was one on Living Systems, specifically animal classification.

One thing we focused on was dichotomous keys.  What?  You’ve never heard of them?  Well before I started teaching about them in 4th grade several years ago, I hadn’t either!  Well at least I didn’t know that’s what they were called.  Let me show you what I mean:

Dichotomous key to determine Silly Scientist names of common items

Dichotomous key to determine Silly Scientist names of common items

The goal is for students to be able to use keys like this to identify animals, but we started somewhere else.  With shoes.  We worked first to CREATE a dichotomous key, so we’d know how it works, and then we practiced using it.

We began by putting everyone’s shoes in a big pile on the floor.  Then, we had to decide two groups that we could classify all those shoes into (see, the dichotomy part–two groups).  Here’s how we started:

Screen Shot 2013-03-24 at 4.32.20 PM

Shoes were put into one of two groups: boots or not boots.

Then, with two groups, we tackled the “boots” pile first.  Again, we asked ourselves what two groups we could make.  This was pretty easy, and so we decided on:

Screen Shot 2013-03-24 at 5.10.32 PM

Only two choices with this one! There were two boots, one was brown and the other was not. We could quickly label those as Natalie and ZB202’s shoes.

Next we had a big ‘ole pile of everyone else’ shoes to classify.  We started like this:

Screen Shot 2013-03-24 at 4.36.59 PM

We looked at shoelaces on all those “not boots.” They all happened to be tennis shoes, by the way.

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Two more: this time looking at the inside of the shoes

Screen Shot 2013-03-24 at 4.43.15 PM

The last step here was pretty easy: only two shoes left, one was a Nike and the other was not. So we could then label one of them as Anna’s and the other as Damonte’s.

Screen Shot 2013-03-24 at 5.04.23 PM

The other side (colored insides) was a little bigger, so needed more groups: tab/no tab, then Nike/not Nike, and pink/not pink and blue/not blue.

After that pile was classified and labeled, we could tackle the other side of the “not boots” bunch, which was colored shoelaces.

Screen Shot 2013-03-24 at 5.14.38 PM

You can see that we had many more small categories in this group, but went through the same process: what two groups could we break the larger one into?

And so once we were finished, our key looked like a beautiful tree, and ended with everyone’s names.  We could now use that key to determine whose shoe was whose.

IMG275

Devan uses our dichotomous key to identify Sophia’s shoe.

Here is Natalie in action, proving how she knows who shoe she has in her hand:

After we had practiced with this dichotomous key that we built, kiddos had a go at the one from the top up there, where they had to identify the silly scientific names of these common items:

1. a die

2. a small paperclip

3. a large paperclip

4. a piece of chalk

5. a popsicle stick

6. a colored marble

7. a white marble

8. a sharpened pencil

9. an unsharpened pencil

10. an eraser

Could you do it?  Use this dichotomous key and tell us what you think the names of each of these items are.  Good luck!

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