Question 9 of 11intermediate🧠 RememberMCQ1 mark

Segmentation in the body is first observed in which of the following:

Exercise: EXERCISES | Q: 13 | (Page 17)
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Explanation

Option (C) Annelida is correct. According to the textbook context, the table clearly shows that Platyhelminthes and Aschelminthes have segmentation marked as 'Absent', while Annelida shows segmentation as 'Present'. The distinctive feature of Annelida is described as 'Body segmentation like rings'. Since Annelida appears before Arthropoda in the evolutionary sequence of animal phyla, segmentation is first observed in Annelida. The text also explains that in animals like earthworms (which belong to Annelida), the body shows metameric segmentation where it is externally and internally divided into segments with serial repetition of organs. Arthropoda also shows segmentation, but Annelida is the phylum where this feature first appears in the animal kingdom.

Solution Steps

  1. Step 1: Check the Segmentation column in the table for each phylum - Platyhelminthes: Absent, Aschelminthes: Absent, Annelida: Present, Arthropoda: Present.

  2. Step 2: Identify that Annelida comes before Arthropoda in the evolutionary sequence of phyla.

  3. Step 3: Conclude that since segmentation is absent in earlier phyla (Platyhelminthes and Aschelminthes) and present in Annelida, segmentation is first observed in Annelida.

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