Question

An open circulatory system occurs in the

• A. Reptiles
• B. Birds
• C. Insects
• D. Annelids

Answer 1

Answer: (C)

Insects

An open circulatory system describes a system where blood and interstitial fluid (fluid found between cells in the body) are allowed to mix in an organism. Organisms that have an open circulatory system don't have true blood since it is mixed with other fluids. The blood in these organisms is defined as haemolymph. Two of the largest phyla in the world, arthropoda and mollusca, have an open circulatory system. Arthropods include most insects and sea organisms like crabs and lobsters. Molluscs are organisms with two shells that are hinged together. Examples include clams and oysters. However, not all molluscs have an open circulatory system. Two major members of the mollusc family, octopus and squid, have a closed circulatory system.