Question

A list of animals is given below. Identify the animals with an open circulatory system and choose the correct answer.
(A) Ascidia
(B) Cockroach
(C) Earthworm
(D) Prawn
(E) Silverfish
(F) Snail
(G) Squid

i. B, D, F, G
ii. B, D, F
iii. C, D, E, G
iv. B, D, E, F
v. A, B, D, F

Answer 1

A system of arteries, veins and capillaries is called vessels. The circulatory system is a network of these vessels which works through a pumping system (heart). It is also known as cardio-vascular system, or simply a vascular system.

Complete answer:
The circulatory system is of two types i.e. open circulatory system and closed circulatory system. In a closed circulatory system, blood is present in the vessels and its flow is unidirectional (from heart to system and then from system back to the heart). It is found in vertebrates.

Open circulatory system is opposite to the closed circulatory system and is found in arthropoda and mollusca. In this system, blood is pumped directly into the body cavity – hemocoel (and not through the blood vessels) where it mixes with the fluid of the body. Such type of blood is known as hemolymph. When the heart pumps, the blood is circulated into the body cavity and to all the organs within it. Then it goes back to the heart through an opening structure known as ostia.

Cockroach, prawn and silverfish come under the category of arthopoda, while snail comes under mollusca. As both arthropods and mollusca have an open circulatory system.

Hence, the correct answer is option (iv) B, D, E, F.

Note: Open circulatory system is not as developed as the closed one. Although it allows movement of gases and nutrients, it does not operate much energy. This could be understood by an example - birds and insects both have the ability to fly, but insects have an open circulatory system while birds have a closed one. Thus insects cannot fly much higher and birds being more developed - have the ability to fly high.