Basis of Animal Classification · NCERT Biology

An incomplete digestive system has:

  1. Two separate openings for mouth and anus
  2. One opening serving as both mouth and anus
  3. No opening at all (absorption through skin)
  4. A mouth opening but no intestine present
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Correct answer: One opening serving as both mouth and anus

Phyla like Platyhelminthes have an incomplete digestive tract where a single opening functions for both ingestion and egestion. A complete digestive system must have two distinct openings.

Difficulty: Medium Question 14 of 20

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