An African clawed frog (Xenopus laevis\textit{Xenopus laevis}Xenopus laevis) is an aquatic amphibian. Like all amphibians, it has a double circulatory system, but its heart contains only one ventricle.
Define the term double circulatory system\textit{double circulatory system}double circulatory system.
Explain why having only one ventricle makes the transport of oxygen to body tissues less efficient than having two ventricles.
Explain why the frog may die if the concentration of dissolved oxygen in the water becomes very low.
44 exam-style questions on AQA GCSE Biology 2.2 Animal tissues, organs and organ systems, covering 2.2.1 The human digestive system, 2.2.2 The heart and blood vessels, 2.2.3 Blood, 2.2.4 Coronary heart disease: a non-communicable disease, 2.2.5 Health issues, 2.2.6 The effect of lifestyle on some non-communicable diseases, and 2.2.7 Cancer. Each one has a worked solution and a mark scheme showing where the marks go.