Continue to classify one group of animals into separate subgroups, using pairs of characteristics, filling in your dichotomous key chart as you go along. Place the second pile of animal cards off to the side for later use.» Write this down on your dichotomous key chart. »This is the first choice in your dichotomous key! Determine a characteristic that will allow you to clearly classify your organism into two categories.Discuss some of the distinguishing characteristics that are easily visible on each of your organisms.When constructing a dichotomous key, you must be aware of the characteristics of the objects you are classifying.»If possible, start different pairs of choices with different words. »If possible, start both choices of a pair with the same word. »Make the choice a positive one – something “is” instead of “is not”. »Use measurements rather than terms like “large” and “small”. »Use constant characteristics rather than variable ones. Best practices when constructing a dichotomous key… There are certain things that should be taken into account when creating a dichotomous key. Quantitative features could include the number of leaves, the length of an organism, how many legs an organism has, etc. Qualitative features could be how an organism looks, its color, if it has a tail, etc. When making a dichotomous key, using both quantitative (numerical) and qualitative (non-numerical) features should be used. A choice in the dichotomous key might be something like, “The flower has white petals or has pink petals.” If the answer was “white petals,” then the next choice might be something like, “The flower has a cone-like structure in the center.” Eventually, when enough choices have been made, the identity of the flower is revealed! How to Make a Dichotomous Key Follow these steps until you have identified all the organisms in question.įor example, let’s say you found a flower on the ground and would like to determine from which plant it came. Move onto the next organism once you have identified the scientific name for the first organism. Then follow the next step it directs you to. You always start with number one on the dichotomous key and determine which of the two characteristics the organism has. When using a dichotomous key, you start with the first organism you want to identify. How to Use a Dichotomous Key to Identify Organisms The purpose of a dichotomous key is to accurately identify the mystery organism. When the user chooses the correct statement, it leads them to the name of the organism. This is the reason that dichotomous keys always provide two choices in each step. “Dichotomous” means “divided into two parts”. Dichotomous keys have a series of statements with two choices that will lead the user to the correct identification of the organism. What is a Dichotomous Key and How Do You Use ItĪ dichotomous key is defined as a scientific tool that is used to identify an organism based on its visible traits. That’s where dichotomous keys come into play. It’s important to have a system to classify these new organisms. No offense to plant lovers, but most kids aren’t too interested in plants…yet!Ĭlassifying organisms is a major component of Biology, therefore, teaching students how to use the dichotomous key is critical! Especially since new species are being discovered all the time. I got so sick of finding the same plant leaf dichotomous key on google that I created my own dichotomous key activity! Once I changed my strategy and started using animals as examples in my keys, they started to learn it much easier. In my early years of teaching, it was a struggle to find fun, relatable keys that were interesting for the kids.
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