Question

Choose an animal that possesses an open circulatory system.
a) Hydra
b) Cockroach
c) Earthworm
d) Octopus

Answer 1

The ability to get around is important for survival. Easy diffusion is used by unicellular organisms to transfer nutrients and waste. Multicellular species have more complex circulatory systems than single-celled organisms.

Complete answer:
Animals have two different types of circulatory systems: open and closed circulatory systems.
Blood vessels carry all fluids into a cavity in an open circulatory system. When the animal walks, the blood inside the cavity flows freely in all directions throughout the body. The blood bathes the organs directly, providing oxygen while also eliminating waste.
Since smooth muscles, which are responsible for blood vessel contraction, are absent, blood flows at a very slow rate. Crabs, spiders, snails, and other invertebrates have an open circulatory system.
Blood never exits the blood vessels in closed circulatory systems, unlike open circulatory systems. Instead, it is continually moved from one blood vessel to the next without ever entering a cavity. Blood travels in one direction, providing oxygen and nutrients to cells while also eliminating waste. Closed circulatory systems are further subdivided into single circulatory systems and multiple circulatory systems.
A fluid called hemolymph is pumped into a blood vessel that empties into the body cavity in open circulatory systems. Hemolymph enters the blood vessel through ostia, which are small openings. Many mollusks and arthropods, like this bee, have open circulatory systems.
Cockroaches have an open circulatory system since they are insects. The cockroach's body cavity is a haemocoel, which contains blood, rather than a true coelom (hemolymph).

The correct Answer is option (B) Cockroach.

Note:
At 27°C, the heart beats at a rate of 100-200 beats per minute. It takes 20-30 minutes for haemolymph to circulate through the body in its entirety.