Question

Blood circulation in earthworm is
A. Closed type
B. Open type
C. Haemoglobin is present in RBC
D. Oxygen not transported by blood

Answer 1

Circulatory system transports the circulatory fluid throughout the body. The blood and hemolymph serve as circulatory fluid in different organisms. The fluid may or may not be transported through blood vessels.

Complete answer:
Circulatory system includes the structures involved in the transport of respiratory gases (oxygen and carbon dioxide), nutrients, waste products, and other substances within the body of the organisms.
When the blood bathes the tissues and the organs, the circulatory system is of open type. On the other hand, when the blood flows through a network of blood vessels and does not bathe the tissues directly, the circulatory system is called of closed type. It is the characteristic feature of annelids and chordates.
Earthworms belong to the phylum Annelida. They do not have special organs for breathing. Their moist skin is the site of gaseous exchange for respiration. Haemoglobin present in the blood plasma serves as a respiratory pigment and carries the oxygen to various structures in each body segment.
However, the haemoglobin protein in earthworms is not confined to the red blood cells (RBCs). Their blood lacks RBCs and therefore, haemoglobin is presently free in the blood plasma. Since their blood flows within the blood vessels and is distinct from the interstitial fluid, they have a closed type of circulatory system. It includes the heart and blood vessels. Two main blood vessels run longitudinally through the body of earthworms to pick and deliver the blood to the structures present in each body segment.

So, the answer is option A. Closed

Note: Basic components of the circulatory system in earthworm are the heart (a pumping organ) and the circulatory fluid (the blood). A set of interconnecting tubes called blood vessels carries the blood between the heart and the body structures. Blood is the medium that transports respiratory gases and other substances to different body parts. In general, blood consists of liquid plasma and blood cells (RBCs, WBCs, and platelets). However, the blood of earthworms does not have RBCs to house the respiratory pigment haemoglobin.