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IB Biology Exam Prep

Category - Biology

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Roundworms are among the most primitive organisms that have a ?
  1. Nerve net.
  2. Digestive tract.
  3. Respiratory organ.
  4. Circulatory system.
Explanation
Correct Answer: B. Roundworms are some of the most primitive organisms to have an actual digestive track consisting of a mouth and anus connected by a digestive tube. More-primitive organisms, such as hydra and jellyfish, have a network of interconnected neurons called a nerve net (A). Roundworms lack both respiratory organs (C) and a structured circulatory system (D).
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