Dichotomous Keys, I’m so lost

Dichotomous Key 2

So I have to say this is the first class I am legitimately worried about failing because I feel like I’m lost. I understood the LEGO example no problem, I get the vocabulary terms, but somewhere combining the two it is like I’m back at square one. I could even figure out how to identify all the bins. So if anyone can take pity on me an post some advice to help me out I would greatly appreciate it.



  1. Katie

    I’m right there with you! It was pretty challenging for me, and I’m not sure that I would be able to ID the bins with out extra resources. I recognized bin 1 from the exercise. For Bins 2 and 3, I used the dichotomous key provided from class, along with pictures from a website (below) to help me figure them out. As for bin 4, I recognized the leaves, catkins, and fuzziness of the plant to figure out it was some type of willow and referred an AK Willow book (also below). Sorry if this isn’t much help! Obviously I’m no master at it either, but the visuals made it kind of easier.

    https://www.fws.gov/WorkArea/DownloadAsset.aspx?id=2147591369 (willows)

  2. I feel the same way! Thanks for posting about your confusion because I thought I was the only one. I even drove 100 miles to a classmate’s home and had my daughter, who has had botany classes, come to my home hoping to figure out what to do. I spent hours upon hours with this assignment, staring at the photos, searching the internet, digging through notes and looking up terminology in the Harris & Harris book. I couldn’t finish it either. It seems like I’m making it more complicated than necessary, but still can’t make heads of tails of where to start on the last bin. I feel your confusion and take pity on you, but won’t be able to help much since I’m in the same boat.

  3. Avatar photo Lucia

    Try thinking of what the plants in each bin have in common (hint: needles are leaves! I just learned that tonight. Thank you, Internet!) and key out the differences on all the leaves together. I don’t know if I took the easy way out but even just focussing on one feature and using all that leaf vocabulary we learned this week, it still took a long time! Good luck!

  4. Dear class,
    Sorry for the confusion, please do not despair. The task was “not” to key out these mystery plants, the purpose of this exercise was to construct a dichotomous fictitious key to the bins. So let’s regroup. There are four bins, each of the bins shows some characteristics that is unique to each bin, some of these characters will apply to multiple bins, so we will eliminate each bin as we go along.
    Bin 1 has needles and cones, the other three bins do not have needles or cones. Thus our first couplet could address these characters:
    A. Plants with needles and woody cones -> bin 1
    A’. Plants with leaves and lacking woody cones -> B

    Now we need to figure out how to divide the other three bins, which characters can we use to separate those from each other. There are those with white flowers and those with purple flowers and another bin that does not seem to have any petals and there are catkins in that bin. So the second couplet could be

    B. Plants with catkins -> Bin 4
    B’ Plants lacking catkins -> C

    I hope this makes more sense now. Sorry if the instructions were not more explicit. The point of the exercise was for everybody to see that the keys can be constructed in different ways, using different characters. You did not had to start out with needles and cones, you could have started out with the catkins or with purple flowers, and separated the rest accordingly… all roads lead to Rome 🙂

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