Classifying and determining the things that are the same and are different between the various creatures is an important step in learning about them. For this reason, a Biological Dichotomous Key is an important thing for students to learn about. A dichotomous key is usually a written device constructed from a series of highly organized statements arranged into couplets (hence "Di"). A couplet is two descriptions which should represent mutually exclusive choices. Both choices are read and compared with the specimen to be identified. Once a decision is made, that selection directs you to another couplet, either the next in order or one further on in the key. This process is repeated until a successful identification is reached. This can be a pretty complicated and abstract concept for younger students.
If it can be learned in a hands-on way, it can make more sense to them, especially if they are in charge of the classifying. One thing that they can classify is different shapes of pasta. For the last few months, every time I cooked pasta, a put a few pieces of it in a plastic container. After I had a pretty large variety of different pasta shapes, I gave them the container and we began to sort them according to various characteristics. Then we created a dichotomous key to identify each pasta. We looked at the different levels of classification and tried to determine them according to Kingdom, Phylum and Order. We did not have enough different characteristics to add in Family, Genus or Species....but we considered painting some stripes or dots and the like on the pasta...
1. Is the pasta either green or purple?
- If green...Kingdom Green... go to question 3.
- If purple...Kingdom Purple
2. Is the pasta either orange or yellow?
- If orange...Kingdom Orange... go to question 4.
- If yellow...Kingdom Yellow... go to question 5.
3. Is the pasta light green?
- If light green...Phylum Light Green...go to question 6.
- If not light green...go to question 7.
4. Is the pasta light orange or medium orange?
- If light orange...Phylum Light Orange...go to question 8.
- If medium orange...Phylum Medium Orange... go to question 9.
5. Is it a bow-tie shape or a corkscrew shape?
- bow-tie shape....Phylum Yellow Bow-Tie
- corkscrew shape...Phylum Yellow Corkscrew
6. Does it have white specks?
- If has white specks...Order Specked Light Green
- If does not have white specks...Order Light Green
7. Is it medium green or dark green?
- If medium green...Phyla Medium Green...go to question 10.
- If dark green...Phyla Dark Green
8. Does it have white specks?
- If it has white specks...Order Specked Light Orange
- If it does not have white specks...Order Light Orange
9. Is it shell shaped or corkscrew shaped?
- If it is shell shaped...Order Medium Orange Shell
- If it is corkscrew shaped...Order Medium Orange Corkscrew
10. Is it shell shaped or corkscrew shaped?
- If it is shell shaped...Order Medium Green Shell
- If it is corkscrew shaped...Order Medium Green Corkscrew
After completing the dichotomous key you can check to see if it works by seeing if other people can follow it through.