1. 1
   In an aquarium, a biology class compared a goldfish, which has a single circulation with blood passing through its heart once for each complete circuit of the body, with a mammal, which has a double circulation with blood passing through its heart twice per circuit, once via the lungs and once via the rest of the body.

   (a)

   In a goldfish's single circulation, blood pressure drops significantly after passing through which structure, before the blood continues on to the rest of the body?

   [1 mark]

   • Aliver
   • Bgills
   • Ckidney
   • Dheart

   (b)

   What is the main advantage of a mammal's double circulation compared with a fish's single circulation?

   [1 mark]

   • Ablood is repressurised at the heart after passing through the lungs, so it reaches the rest of the body at a higher pressure
   • Bblood is sent around the whole body twice for every heartbeat
   • Cit reduces the total volume of blood needed in the body
   • Dit removes the need for arteries, capillaries and veins

   (c)

   Explain why a mammal's double circulation delivers oxygen to its body tissues more effectively than a fish's single circulation.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student used a stethoscope to listen to a volunteer's heartbeat and recorded the order in which the chambers of the heart contracted and the valves opened and closed, alongside noting the relative thickness of the heart's muscular walls.

   (a)

   Which structure prevents blood flowing backwards from the ventricles into the atria when the ventricles contract?

   [1 mark]

   • Asemilunar valves
   • Bseptum
   • Catrioventricular valves
   • Dcoronary arteries

   (b)

   Why is the muscular wall of the left ventricle thicker than that of the right ventricle?

   [1 mark]

   • Abecause it contains more valves
   • Bbecause it is the chamber that receives blood returning from the body
   • Cbecause it only has to pump blood a short distance, to the nearby lungs
   • Dbecause it must pump blood at high pressure all the way around the body, whereas the right ventricle only pumps blood to the nearby lungs

   (c)

   Describe the sequence of chamber contraction and valve action during a single heartbeat, starting from when the atria contract.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A technician compared tissue samples taken from an artery and from a bed of capillaries in the same organ, examining the thickness of the vessel walls and the width of the space through which the blood flows.

   (a)

   Explain how the structure of an artery is related to the pressure of the blood it carries.

   [3 marks]

   (b)

   Explain how the structure of capillaries is related to their function of exchanging substances with body tissues.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A patient with a wound to the leg was found to have an unusually low platelet count, together with anaemia caused by a reduced number of red blood cells, and was later found to have an infection that had raised the number of white blood cells in a blood sample.

   (a)

   Explain the roles of red blood cells, white blood cells and platelets in the blood, and explain why a low platelet count would put this patient at greater risk following the wound to their leg.

   [6 marks]

   (b)

   Explain, referring to the heart and blood vessels, how this patient's raised number of white blood cells would be carried from where they are produced to the site of infection in their leg, and explain how clotting at the wound helps to protect against further infection.

   [6 marks]

   Total for question 4: 12 marks

5. 5
   A doctor ordered a full blood count for a patient recovering from surgery, checking the numbers of red cells, white cells and platelets present, alongside timing how quickly a small cut on the patient's finger stopped bleeding.

   (a)

   Which component of the blood transports carbon dioxide, dissolved ions, hormones and nutrients around the body?

   [1 mark]

   • Aplasma
   • Bred blood cells
   • Cwhite blood cells
   • Dplatelets

   (b)

   What is the main function of red blood cells?

   [1 mark]

   • Aengulf pathogens by phagocytosis
   • Btransport oxygen around the body, bound to haemoglobin
   • Cproduce antibodies against pathogens
   • Dform a mesh during blood clotting

   (c)

   Explain why red blood cells having no nucleus is an advantage for their function.

   [2 marks]

   Total for question 5: 4 marks

6. 6
   A cardiologist attached an ECG monitor to a patient, measured their pulse rate at the wrist, and listened to their heart sounds through a stethoscope, in order to check that the heart's electrical activity, rate and valve action were all normal.

   (a)

   What does an ECG (electrocardiogram) measure?

   [1 mark]

   • Athe volume of blood in the ventricles
   • Bthe pressure of blood in the arteries
   • Cthe number of red blood cells present
   • Dthe electrical activity that triggers each heartbeat

   (b)

   What produces the two sounds heard through a stethoscope during a heartbeat?

   [1 mark]

   • Ablood flowing through the aorta
   • Bcontraction of the ventricular muscle
   • Cthe closing of the atrioventricular and semilunar valves
   • Dair moving into the lungs

   (c)

   Explain why a doctor can use a patient's pulse rate as a way of measuring their heart rate.

   [2 marks]

   Total for question 6: 4 marks

7. 7
   A researcher compared the wall thickness, lumen diameter and presence of valves in samples taken from a vein and an artery from the same region of the body, and separately investigated a patient whose coronary arteries had become narrowed by fatty deposits.

   (a)

   Explain how the structure of a vein differs from that of an artery, and relate these differences to the function of veins.

   [3 marks]

   (b)

   Explain how coronary heart disease develops, and describe two risk factors that increase a person's chance of developing it.

   [4 marks]

   Total for question 7: 7 marks

8. 8
   A student compared two model organisms: a fish, with a single circulation, gills and a two-chambered heart, and a mammal, with a double circulation, a four-chambered heart and lungs, in order to understand how heart structure, blood vessel structure and blood composition together allow the mammal to sustain a much higher and more constant level of activity than the fish.

   (a)

   Explain how the structure of the mammalian heart and its blood vessels work together to deliver oxygenated blood to body tissues at high pressure, and explain why this would not be possible with a fish's single circulation and two-chambered heart, which pumps in series with the gills.

   [6 marks]

   (b)

   Explain how the mammal's blood composition (red blood cells, white blood cells and plasma) supports its higher and more constant level of activity compared with the fish.

   [6 marks]

   Total for question 8: 12 marks

End of questions