HardBiologyHigh School (11–12)Diversity of Living Organisms › Basis of Animal ClassificationConceptual
Sohan says: "An earthworm has segments, a true coelom and closed circulation, so it must be a…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Sohan says: "An earthworm has segments, a true coelom and closed circulation, so it must be a chordate."
- Which of these features do earthworms share with chordates?
- Which feature decides whether an animal is a chordate?
- Is Sohan right?
Need a reminder? The key ideaShow
Metameric segmentation: the body is divided outside and inside into segments, with some organs repeated (annelids, arthropods, chordates). The notochord is a rod formed from mesoderm on the dorsal side of the embryo; chordates have it. Key: cellular level, Porifera; radial and diploblastic, Coelenterata or Ctenophora; bilateral and triploblastic: no cavity, Platyhelminthes; pseudocoelom, Aschelminthes; coelom, Annelida to Chordata.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) Earthworms share segmentation, a true coelom and closed circulation with chordates.
Step 2. (b) The notochord, a rod from the mesoderm on the dorsal side of the embryo, decides it.
Step 3. (c) Earthworms never form a notochord, so they are non-chordates. Sohan is wrong: shared features do not make the group.
Answer: (a) segments, coelom, closed circulation; (b) the notochord; (c) no.
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