Question

(a) Name the red pigment which carries oxygen in the blood.
(b) Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
(c) How many chambers are there in the heart of : (i) an amphibian, (ii) a mammal, and (iii) a fish?
(d) Describe the circulatory system in a fish.

Answer 1

(a) Haemoglobin is the red colour pigment that carries oxygen in the blood.

(b) Mammals and birds are warm blooded animals. Their energy requirement is high since they constantly require energy to maintain their body temperature. Hence, it is necessary to separate the oxygenated and the deoxygenated blood in mammals and birds as this separation allows a highly efficient supply of oxygen to the blood cells. This is important for producing a lot of energy and for maintaining the body temperature.

(c) (i) An amphibian, such as a frog, has a three-chambered heart, with two auricles and one ventricle.
(ii) A mammal has four-chambered heart. The upper two chambers are called atria and the lower two chambers are called ventricles.
(iii) A fish has only two chambers in its heart, i.e. one auricle and one ventricle.

(d) A fish has a two-chambered heart with one auricle and one ventricle. Since both the auricle and ventricle remain undivided, only deoxygenated blood passes through it. The deoxygenated blood passes from the ventricles into the gills for oxygenation. The oxygenated blood from the gills is then passed to the body parts of the fish where oxygen is utilised and carbon dioxide enters it, thereby making the blood deoxygenated. The deoxygenated blood then returns to the heart to be pumped again into the gills for oxygenation.
Since the blood passes through the heart of the fish only once in one complete cycle of the body, the flow of blood in a fish is known as single circulation.