Mass transport and the mammalian heartEdexcel A-Level Biology A: Mind map

Exam questions on Mass transport and the mammalian heart

1. A flatworm is a flat animal about 1 mm thick with no heart or blood. It obtains oxygen and nutrients directly from the surrounding water. A mouse is a small mammal with a very high metabolic rate, a heart and a circulatory system.
   Explain why the mouse needs a heart and circulatory system.2 marks
2. In a practical lesson a student dissects a sheep's heart. She cuts across both ventricles to compare the walls and then opens the atria and ventricles to look at the valves.
   Explain why the wall of the left ventricle is thicker than the wall of the right ventricle.2 marks
3. In a healthy adult at rest one cardiac cycle lasts 0.8 s. Atrial systole lasts 0.1 s, ventricular systole lasts 0.3 s and cardiac diastole lasts 0.4 s. During ventricular systole the pressure in the left ventricle rises from about 0.5 kPa to about 16 kPa, while the pressure in the aorta is about 11 kPa.
   Explain how the pressure changes in the left ventricle control the opening and closing of valves during ventricular systole.3 marks