CIE iGCSE Co-Ordinated Science B9.1 Circulatory systems Exam Style Questions Paper 4
Question
(a) Mammals have a double circulatory system. Fish have a single circulatory system.
Fig. 1.1 shows the circulatory system of a fish and the circulatory system of a mammal.
(i) Use Fig. 1.1 to describe two ways the circulatory system of a fish is different from the circulatory system of a mammal.
▶️Answer/Explanation
1. Fish have a single circulatory system where blood passes through the heart once per complete circuit, while mammals have a double circulatory system where blood passes through the heart twice per complete circuit.
2. Fish hearts have only two chambers (one atrium and one ventricle), while mammalian hearts have four chambers (two atria and two ventricles).
(ii) Explain one advantage of having a double circulatory system.
▶️Answer/Explanation
A double circulatory system maintains higher blood pressure to body tissues, allowing for more efficient delivery of oxygen and removal of waste products. It also prevents delicate lung tissues from being damaged by high pressure blood flow.
(b) Table 1.1 shows the diameter and the thickness of the wall of two different blood vessels in humans.
(i) Calculate the difference in thickness of the wall of the aorta and the vena cava.
▶️Answer/Explanation
2.0 mm – 1.5 mm = 0.5 mm
(ii) Explain why the walls of the aorta and the vena cava need to be of different thicknesses.
▶️Answer/Explanation
The aorta has thicker walls because it needs to withstand higher blood pressure as it carries oxygenated blood directly from the heart. The vena cava carries deoxygenated blood at lower pressure back to the heart, so its walls can be thinner.
(c) Red blood cells transport oxygen around the body.
(i) Describe two ways red blood cells are adapted for their function.
▶️Answer/Explanation
1. Biconcave shape increases surface area for oxygen absorption
2. Contain hemoglobin which binds to oxygen molecules
3. Lack a nucleus to maximize space for hemoglobin (any two)
(ii) State two other major components of blood.
▶️Answer/Explanation
1. White blood cells
2. Platelets
3. Plasma (any two)