SME
Principles of Biology II · Problem type
Keying invertebrates
Use this for “It has jointed legs, but eight of them, not six. Where does the key place it?”
Explore
Jointed legs split the five at once: the arthropods go one way, the soft-bodied animals the other.
Assumptions
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A dichotomous key asks one yes-or-no question at a time about a trait you can see on the specimen.
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Each answer leads to the next question or to a name, so every path ends at exactly one group.
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Jointed legs mark the arthropods; among them, six legs mark the insects and eight the arachnids.
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