Linnaeus lumped all of the worm-like animals into the category Vermes (Vermis is Latin for worm). Is this a valid classification scheme?

Question

A.  No, because some worms are protists.
B.  Yes, because all worms are members of the same phylum.
C.  Yes, because all worm-like animals are more closely related to each other than they are to other animals.
D.  No, because the worm-like body plan has appeared many times through evolutionary history and is not a useful trait for classification.

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?

Gather Content
· What do you already know about animal classification?

Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

D.  No, because the worm-like body plan has appeared many times through evolutionary history and is not a useful trait for classification.

Clarify Question
· What is the key concept addressed by the question?
        o This question addresses animal classification.
· What type of thinking is required?
        o This question is asking you to weigh and judge evidence, or evaluate, to choose the best of the possible answers.

Gather Content

· What do you already know about animal classification?
        o Animals are classified according to their evolutionary relationships.
        o In cladistics, scientists attempt to group animals into monophyletic clades – that is, a group in which all members are more closely related to each other than any members are to another type of organism.

Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Consider some different types of “worms”:
        o Acoel flatworms – In the phylum Acoela, the sister group to all other Bilateria.
        o Platyhelminthes – Flatworms like planaria.
        o Annelida – Segmented worms, including earthworms and leeches.
        o Nematoda – Tiny roundworms, such as C. elegans.
        o Nemertea – A group of marine worms.
        o Chaetognatha –Arrow worms, which have an uncertain phylogenetic placement.
        o It is clear that the worm body plan has been a common solution hit upon during evolution of the animals. It has appeared many times through evolutionary history and is not a useful trait for classification.

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o The question required you to weigh and judge evidence, or evaluate, to choose the best of the possible answers.
        o Did you recognize that “worm” body plans are common in distantly-related animal phyla, and thus provide no useful classification information?