Dichotomous Keys

This is a follow-up lesson from our last lesson on natural selection.  I would have liked to have spent more time on understanding it and having the kids explain natural selection in their own terms, but there is just no time.  So today we moved on to dichotomous keys and kind of did a small review on natural selection in our bell ringer.  The concept of natural selection is intuitive, but truly being able to answer a variety of question types on it.  Oh well.

So now we're doing Dichotomous Keys, and that finishes the week (I only got to see my seventh graders twice this week).  So next week is complete review, and the week after that is the state test!

After first explaining what a dichotomous key is and how it works, I handed out the following worksheet and did the first three with them, and then let them do the rest with a partner.  Dichotomous keys aren't hard to use, so kids get the gist of it really quick.  I felt that it was an important part of the evolution unit and might be on the state test. I might also be completely wrong.  We'll see!


Here's a preview of the worksheet.  To download, scroll to the bottom of the page.

I then found this wonderful worksheet on the web.  I did not make this!  Someone else who was talented (and probably beautiful!) made this worksheet and gracefully had it up for free on the internet.  I thought it was so good, however, that I wanted to post it here, too.  I love it because it has a very well done dichotomous key, and then it has the little opportunity for the kids to do one, too.

 Now, you can choose to do this some other way.  In fact, we had extra time, so I had everyone put one of their shoes in the middle, and we made another dichotomous key together for our shoes.  Some kids gladly took their shoes off and others took a lot more convincing–– lots  of funny comments:

"Miss, my shoes are really hot and smelly."

"Eww, Miss!  His feet stink!!!"

"They're going to laugh at my socks!"

"I'm not wearing any socks!"  What?  Where are your socks??

After pulling teeth with one girl to take one of her shoes off, she said, "Oh. . . I feel like I'm in my house."

Scroll to the bottom to download the worksheet I found that someone else had made.  Preview: