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2 marksThe Circulatory System of Mammals

CAPE Biology Unit 2 · May/June 2025 · Paper 2 · Question 2(a)(ii)

The cardiac cycle is a sequence of events forming one heartbeat. The rhythmic contraction of the heart muscle is initiated and controlled by structures and tissues within the heart. The heart muscle is described as myogenic.

State ONE role of EACH of the following structures in the heart during the initiation and coordination of the cardiac cycle: Sinoatrial node (SAN), Purkyne tissue.

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Other parts of this question

  1. 2(a)(i)Define the term 'myogenic'.[2 marks]
  2. 2(a)(iii)Use the information in Figure 2 to calculate the heart rate in beats per minute.[2 marks]
  3. 2(a)(iv)Using the information in Figure 2, state ONE reason why Point X indicates the opening of the semilunar valve of the aorta.[1 mark]
  4. 2(a)(v)Label the graph in Figure 2 using an arrow and the letter Y to show when the atrioventricular valves open.[1 mark]
  5. 2(a)(vi)Label the graph in Figure 2 using a double-ended arrow and the letter Z to show when the ventricle is being filled with blood.[1 mark]
  6. 2(b)(i)Define the term 'excretion'.[2 marks]
  7. 2(b)(ii)Outline ONE reason why the main nitrogenous waste product excreted by mammals is urea rather than ammonia.[2 marks]
  8. 2(b)(iii)Draw a diagram of the bordered structure shown in Figure 3 in the space provided below.[5 marks]
  9. 2(b)(iv)The convoluted tubule shown in Figure 3 is adapted for reabsorption. Outline ONE adaptation of the epithelial cells of the proximal convoluted tubule that…[2 marks]
  10. 2(c)(i)State ONE reason why there is a difference between the quantity of water in the glomerular filtrate and the quantity of water in the urine.[1 mark]
  11. 2(c)(ii)Explain the differences in the concentration of EACH of the following substances in blood plasma, glomerular filtrate and urine as shown in Table 2. You MUST…[9 marks]

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