Instructor Demonstration: Dichotomous key to music formats
1. It is a rectangle …… a cassette tape.
It is a circle …… go to 2.
2. It is larger than 13.0 cm …… go to 3.
It is smaller than 13.0 cm …… go 4.
3. It is less than 18.0 cm …… 45 rpm vinyl record.
It is greater than 18.0 cm …… 33 rpm vinyl record.
4. It is exactly 12.0 cm …… digital album.
Note: in the absence of any markings, it is nearly impossible to indicate if it is a
CD, DVD, or Blu-ray disc.
In the example above, it is possible to see how a dichotomous key can be used to distinguish different formats containing music. However, unless the digital discs have labels, it is nearly impossible to tell apart a CD, DVD, and Blu-ray disc. This is because they are cryptic. Can you tell apart these three disc types by looking only at their reflective bottoms? There are no labels on organisms, which means cryptic species are usually separated by sequencing DNA. With these three types of digital albums, the data formats of each disc are different, similarly to how the DNA code is different between cryptic species.
How would you go about telling the difference in data structure and format
between the three disc types? _________________________________________
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III. MATERIALS
• Activity 1
o Assorted nails and screws
o Ruler
o Dichotomous key to the nails and screws provided below
• Activity 2
o Various plastic toy dinosaurs
IV. METHODS AND RESULTS
Activity 1: Identifying nails and screws
Overview
In this activity you will:
• use an existing dichotomous key
• familiarize yourself with dichotomous logic
Objectives
After doing this laboratory activity you should be able to:
• understand dichotomous key methodology
• identify the specific names of unknown specimens by using a dichotomous key
Methodology
The instructor will divide the class into groups of two students each. With your lab partner, inspect all of the different nails and screws in the container on your lab bench. Each piece of hardware is unique, even if some look a lot alike. Some are for similar applications while some are for very different uses. You may be able to generally identify the type of each piece of hardware, but can you provide the specific name for each piece?
In this exercise, you will be able to determine the specific name for each piece of hardware. Randomly draw a nail or screw from the container and use the dichotomous key to work through the naming steps. Repeat this until you have drawn all pieces from the container. When completed, you will know the exact name of every piece of hardware at your bench. This is a lot like how biologists sort through their samples. For example, a fish biologist may take a net to a river and randomly scoop up many species of unknown fishes. A dichotomous key will identify the name of each fish species in the net.