Biology Edexcel A level Comprehensive Exam With Solved Solutions 2024.

It's dipolar so it's a good solvent. And it has strong hydrogen bonds therefore it's cohesive - Answer Why is water good for transport? Gas exchange doesn't happen efficiently through diffusion so substances need to be transported around the body to organs - Answer Why do multicellular organisms need a mass transport system? Atrium systole - Answer What is it called when the atrium contracts and the AV valves open? Ventricle systole - Answer What is it called when the AV valves close, the ventricles contract and the semilunar valves open, allowing blood flow to leave the heart? They need more muscle to pump blood around the whole body - Answer Why are the ventricle walls thicker than the atrium? cardiac diastole - Answer What is it called when the semi lunar and AV valves are closed and the heart is relaxed in low pressure? To supply oxygen to the heart - Answer Why do we have coronary arteries? To prevent backflow - Answer Why do we need valves? To cope with high pressures - Answer Why do arteries have a folded endothelium, thick muscular walls and elastic tissues? Large lumens, thin walls - Answer What do veins have?