Living Environment
Student Work
BSC Lesson # 9
Lesson 9. Dichotomous Keys
Name:
Period ______
Laboratory Experience ##
Worth ### Lab Minutes
Date :
Bridge
We have been doing a lot with characteristics and relationships. What
have we looked at to identify these relationships?
Objective:
To use structural
characteristics in
order to identify
an organism
(taxonomy and
classification)
Essential
Question:
How can I use
characteristics
and a specific
scientific tool
(dichotomous
key) to identify a
specimen?
Mini Lesson
Characteristics or traits are the easiest way to identify organisms. Scientists know that there are
millions of different species on Earth, but they also know that there are many more they have yet
to discover. Observation of an organism alone is enough to give the species a name and to
place it into one of the kingdoms, but there needs to be a way for them to identify differences
between species that look very much alike or to identify an organism they come across to find
out if it is a new species or an already existing one.
Scientists use a tool to help them do this. This tool is a dichotomous key. The idea behind this
tool is to take characteristics and methodically separate organisms from each other based on
these traits until you have the specific name of the organism.
Let’s take a look at a dichotomous key.
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Living Environment
Student Work
BSC Lesson # 9
Take your fish cards and place them into groups based on their characteristics (do this in pairs).
Since we still don’t know their names, we can use these same characteristics that we used to
group them to figure out what they are. Use the fish key on the next page with your pictures to
identify each kind of fish and see if you can find the trick to reading a dichotomous key! We will
then label each of them as a class (do not label them below until we go over them)
Work Period
Fish key
Step 1
If fish shape is long and skinny, then go to step 2
If fish shape is not long and skinny, then go to step 3
Step 2
If fish has pointed fins, it is a trumpet fish
If fish has smooth fins, it is a spotted moray eel
Step 3
If fish has both eyes on top of the head, then go to step 4
If fish has one eye on each side of the head, then go to step 5
Step 4
If fish has long whip-like tail, it is a spotted eagle ray
If fish has short, blunt tail, it is a peacock flounder
Step 5
If fish has spots, then go to step 6
If fish does not have spots, then go to step 7
Step 6
If fish has chin "whiskers," it is a spotted goat fish
If fish does not have chin "whiskers," it is a band-tail puffer
Step 7
If fish has stripes, then go to step 8
If fish does not have stripes, it is a glassy sweeper
Step 8
If fish has a v-shaped tail, it is a squirrel fish
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Living Environment
Student Work
BSC Lesson # 9
If fish has a blunt tail, it is a glass-eye snapper
Summary
How can I use characteristics and a specific scientific tool (dichotomous key) to identify a
specimen?
Closing
1. A dichotomous key is shown below.
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Living Environment
Student Work
BSC Lesson # 9
Use the dichotomous key to identify the scientific name of the organism represented
below. [1]
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Living Environment
Student Work
Name:
BSC Lesson # 9
Period ______ Date :
Independent Practice
Regents questions on dichotomous keys…. Specifically the one with the chart and the fish
and the one with the spotted bugs and wings
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Living Environment
Student Work
Name:
BSC Lesson # 9
Period ______
Date :
Title of Lab: ______________________________________________________
Exploration
Use this space to record observations that relate to the question being investigated. Also record
researched facts that might relate to the investigation as well.
Question
Record your question that you will be investigating here. It is best to write it in a “Does
__________________ affect ________________? Format so the variables are easy to identify (first
line is always the independent variable, second line is always the dependent variable)
Identify your Variables
Independent Variable:
Dependent Variable:
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Living Environment
Student Work
BSC Lesson # 9
Prediction/Hypothesis
Based on the question that you asked, record your thoughts on what the result will be and why. Use
the “I think ___________________________________, because ______________.” format.
Experimental Design
List the materials that you are going to use and the procedure (steps) you are going to take to test your
hypothesis.
Materials:
Procedure:
Data Collection
Use this space to organize and collect your data. Remember, data can be qualitative (descriptions,
words, observations) as well as quantitative (numbers, values). Use both kinds of data when you can.
Organize your data into a table with a title, make a graph whenever you can, and use the variables to
help you do this!
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Living Environment
Student Work
BSC Lesson # 9
Data Analysis
Put your data into words. This will be a relationship of your variables: what happened to the dependent
variable when you changed the independent variable?
Evaluation
This is where you talk about your experiment. Discuss how your results compare to your hypothesis:
do you agree or disagree with your original thoughts and use evidence from your experiment to back
this up. Second, discuss sources of error (at least 2), or things that could have gone wrong in your
experiment. Finally, develop a further investigation question: based on what you found out in this
experiment, what else do you wonder about? Again, use your “Does ________ affect __________”
format for this question.
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