Question

Fish demonstrate numerous strategies to give them advantages in bodies of water. Yet, one disadvantage of their body plan is a less efficient cardiovascular system than the other chordates. Outline the cardiac and respiratory systems of the fish and describe why they are sufficient in this group.

Answer 1

Outline of Cardiac and Respiratory system of Fishes

The gaseous exchange occurs through Gills in fishes.Gills help in exchange of carbondioxide, oxygen, ammonia, ions... Gills have thread like structures called Filaments. The filaments have capillary network which increases the surface area for exchange of gases. There are accessory respiratory organs in many fishes as a mode of adaptation. Mudskippers breathe through their skin, catfish through gut, electric eel through buccal cavity are some examples. Some modern fishes have Hydrostatic organ called swim bladder, which is a highly vascularized breathing organ. Fishes also utilize counter current mechanism for diffusion of gases.

Fishes have a closed loop circulation. It consists of heart, arteries, capillaries, and veins. It is an example of single circulatory system- blood passes through the heart only onceThe heart of fish have two chambers, an atrium and a ventricle. There is also a tube shaped structure known as BUlbus arteriosus and another structure known as Sinus venosus.Bulbous arteriosus maintains continous blood flow into gill arches. Arteries carry oxygenated blood from gills to all parts of the body, Veins carry deoxygenated blood from body parts to the heart. The capillaries are minute vessels that form a network called Capillary bed , where capillary and venous blood gets linked. The heart recieves blood from the veins and pass into gills,where carbon dioxide is replaced with oxygen.