Lesson: Chapter 13 — The Living World

13.1. Invertebrates 4 of 8 Reset answers

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Question 4

In which phylum did the body cavity called the coelom first develop?

A Mollusca B Arthropoda C Annelida D Cnidaria

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Annelida — the phylum of segmented worms, holding the earthworm, the leech and the ragworm.

Cnidarians have no coelom at all, being diploblastic. Molluscs and arthropods do bear one, but it was first seen in the annelids.

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