Question

1. when oxygen is lost from blood the colour of the blood without the oxygen changes

a. from pink to red d. from red to blue
b. from red to pink e. from blue to red
c. from pink to blue

1. which of the following is not true

a. mammalian heart has four chambers
b. amphibian heart has 3 chambers
c. aves heart have four chambers
d. pisces heart have three chambers
e. all of them are correct

1. which structure is used at the mouth of aorta

a. tricuspid valve d. bicuspid
b. semilunar valve e. pulmonary
c. s - a node

1. which part of the heart is thicker

a. left atrium
b. left ventricle
c. right atrium
d. right ventricle
e. all of them are same

1. which of the following is not found in the thoracic cavity of man.

a. heart d. superior vena cava
b. lungs e. stomach
c. bronchi

Explanation:

• Question 6: Oxygenated blood is bright red, de - oxygenated blood is darker (often described as a bluish - red in some contexts, but in standard textbook terms, when oxygen is lost, it changes from red to a darker shade which can be approximated as a change from red to blue in the given options).
• Question 7: Aves (birds) have a four - chambered heart. So the statement “Aves heart have four chambers” is correct. Mammalian hearts have four chambers, amphibian hearts have three chambers, and Pisces (fish) hearts have two chambers.
• Question 8: The semilunar valve is located at the mouth of the aorta (and also at the mouth of the pulmonary artery). The tricuspid valve is between the right atrium and right ventricle, the bicuspid (mitral) valve is between the left atrium and left ventricle, and the S - A node is the sino - atrial node (a part of the heart's conduction system).
• Question 9: The left ventricle has the thickest wall because it needs to pump blood to the entire body (systemic circulation), requiring more force.
• Question 10: The stomach is located in the abdominal cavity, while the heart, lungs, bronchi, and superior vena cava are located in the thoracic cavity.

Answer:

• 6. d. from red to blue
• 7. c. Aves heart have four chambers (this option is correct, so the one that is not true would be if we consider mis - information. But if we assume the question is which is not a wrong statement, then all the other options about heart chambers for different classes (except for Pisces in option d which has two chambers) have correct chamber numbers as per the question's options. But if we follow the normal biological facts: Pisces - 2 chambers, Amphibian - 3, Mammals - 4, Aves - 4. So if the question is “which is not true” and option d says “Pisces heart have three Chambers” (assuming a typo in the original question where option d was mis - written as three instead of two), then option d is not true. But based on the given options as written:
• If we assume the options are as written (Pisces heart have three Chambers in option d which is wrong as Pisces have two), then the answer for question 7 is d.
• 8. b. Semilunar valve
• 9. b. Left ventricle
• 10. e. stomach