how to make a dichotomous key

What is a dichotomous key? A key for the identification of organisms using paired statements These statements must be opposites For example, if the first statement is “has blue eyes,” then the paired statement would be: Has green/brown/hazel eyes Does not have blue eyes

So how do I make my own dichotomous key? Make a list of things that you want to classify: Let’s classify restaurants Red Lobster McDonalds Chili’s Cracker Barrel Chick Fil A

So how do I make my own dichotomous key? Group the restaurants into two groups those with drive-thrus those without Write paired statements, one reflecting each group type those with drive-thrus = “has a drive-thru” those without drive-thrus = “has no drive-thru”

So how do I make my own dichotomous key? Each statement is like a map. It tells you where to go next. Read the statement and look at the things that you are trying to classify. How many items match that statement? If it is one, write the name of the item If it is more than one, you need another way to divide the group Go to #(next available number)

So how do I make my own dichotomous key? So in our example, the first statement “has a drive-thru” matches two of the restaurants: McDonalds Chick Fil A So it needs another way to divide them Go to #2

So how do I make my own dichotomous key? The second statement “has no drive-thru” matches three restaurants: Red Lobster Chili’s Cracker Barrel So we need another way to divide them: Go to #3

So how do I make my own dichotomous key? For #2, we need to divide McDonalds and Chick Fil A serves hamburgers doesn’t serve hamburgers Each statement has exactly one match, so we are done with those two restaurants serves hamburgers = McDonalds doesn’t serve hamburgers = Chick Fil A

So how do I make my own dichotomous key? For #3, we need to divide Red Lobster, Chili’s, and Cracker Barrel Serves breakfast Doesn’t serve breakfast One statement has exactly one match Serves breakfast = Cracker Barrel The other statement has two matches, so we need another category Doesn’t serve breakfast = Go to #4

So how do I make my own dichotomous key? For #4, we need to separate Chili’s and Red Lobster Serves whole lobsters= Red Lobster Doesn’t serve whole lobster = Chili’s Now all five restaurants are in groups by themselves. Our dichotomous key is complete!

I know how to make one.. Now how do I read one? Pick one of the items that you are trying to classify ALWAYS start with #1! Determine which statement matches the item that you are trying to classify, and follow the direction that statement gives you Once you have classified that item, pick another item until the key is complete!