Thought Questions 15. a. Does the circulatory system of fishes have a pulmonary
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Thought Questions 15. a. Does the circulatory system of fishes have a pulmonary circuit? Explain your answer iven the attachment of gills to the pharynx, explain the absence of a trachea in fishes and the need for a trachea in mammals. 16. What is the role of the four-chambered hearts of birds and mammals in maintaining a warm body temperature? 17. a. Which of the animals studied in this laboratory exercise have a rib cage? Explain the importance of a rib cage respiration. b. Which of the animals studied in this laboratory exercise have a diaphragm? Explain the importance of a diaphragm to respiration. 438 Laboratory 29 The VertebratesExplanation / Answer
15 a. In fishes we observe a single systemic circuit of blood flow. They have two chambered heart with one atrium and one ventricle. Heart pumps the blood to gills where it is reoxygenated after which the blood flows to rest of the body and back to heart.
15 b. As described in the previous answer fishes have single circulation of blood from heart to gills and then from gills to rest of the body and back to heart. The laryngotracheal groove which in humans form larynx, trachea and lungs develops into airbladder in fishes. The air bladder is even called lungs in lung fishes. Mammals have a tube like tracheal system which connects the lungs to the outside. Trachea is developed in mammals which carries the air till lungs due to the absence of any surface structure for the exchange of gases like gills in fishes.
16. Birds and mammals have four chambered heart. The 4 chambered heart prevents the mixing of oxygenated and deoxygenated blood thus increasing the efficiency with which oxygen is transported by blood. Birds and mammals need energy constantly for maintaing their body temperature thus it is advantageous for them to have 4 chambered heart.
17. The rib cage help in respiration with the help of a pair of muscles present inbetween the ribs i.e. external and internal intercoastal muscles.
18. Diaphragm was first evolved in mammals. it has phrenic muscle whose contraction and relaxation helps in inhaling and exhaling air. Conraction of diaphragm muscle increases the thoracic volume in humans thereby decreasing the pressure. As air moves from high pressure to low pressure area thus air enters into the lungs in thoracic region. Vice-versa happens during exhalation.
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