Question

Which of the following are the first to have closed circulatory system?

• A. Molluscs
• B. Annelids
• C. Arthropods
• D. Echinoderms

Answer 1

Answer: (B)

Annelids

The circulatory patterns are of two types open or closed. Open circulatory system is present in arthropods and molluscs in which blood pumped by the heart passes through large vessels into open spaces or body cavities called sinuses. Annelids and chordates have a closed circulatory system, in which the blood pumped by the heart is always circulated through a closed network of blood vessels. This pattern is considered to be more advantageous as the flow of fluid can be more precisely regulated.

So, the correct answer is option B.