Ugh Dichotomous Key?

Question

mmk i have to make a lil dichotomous key for biology.. with beetles. Its an EC assignment and i have no idea what im doing. Could anyone possible help out? All i have is a picture of the beetles i have to make the key with. I scanned it from the book and here are the beetles:

http://i102.photobucket.com/albums/m112/clanstuff/beeetles.jpg

Doesnt need to be long unless thats what you want, and no big words that i , a 14 yr old, wouldnt say lol. Like the first branch off could be round, or oval or something. Im just confused on what to do and how to divide characteristics and get all the beetles in there.

Answer 1

Dichotomous key is a step by step way to classify a group of things, in your case these beetles. You pick a physical trait (since all you have are pictures) and divide your sample into two groups. You could pick things like body size, shape, color, size/shape of legs, antenna, etc. Start with whichever one you want. Then, with one group, find another trait and divide them into two more groups. You can repeat this trait for the other side if you like. If you're really good at dichotomous keys, you can do it so that at the end, you're left with only 1 beetle in each group.

One possibility to start with: body shape-oblong vs round...such as beetles 1, 2, 3 are all oblong whereas 4, 5, 6 are round (but classify all the beetles). The second trait could be horizontal vs vertical stripes on the body...such as 1 and 2 are horizontal but 3 is vertical (but don't forget to break down 4,5, 6 also). Then the third trait could be long vs short antennae...such as 1 has short and 2 has long...

It doesn't matter really as long as people could follow your key and classify the beetles the same way you did so you have to make the traits "mutually exclusive" meaning your beetles could only be this choice OR this choice, no other possibilities. You can "semi-cheat" and say brown color vs not brown color cuz you can only have 2 choices, but you'd have 3 possible colors...

Hope this helps!

Answer 2

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RE:
Ugh Dichotomous Key?
mmk i have to make a lil dichotomous key for biology.. with beetles. Its an EC assignment and i have no idea what im doing. Could anyone possible help out? All i have is a picture of the beetles i have to make the key with. I scanned it from the book and here are the beetles:...

Answer 3

There is no right or wrong way to do a dichotomous key, but some ways are better than other. It works best by starting with the feature that differs the most, and then its really just a process of elimination. If you start with round or elongate bodies, you work your way down through the differences in the round-bodied beetles until they are all classified, then do the same for the elongate beetles. I think I would start with the antennae - some are long, some short, some curved and some have bends, but you could also do antennae after splitting them into round and elongate.