6 exam-style questions with full mark schemes and model answers. Write your own answer and the AI examiner marks it against the mark scheme.
Learn this properly: The Heart and Circulatory SystemGas exchange in the lungs takes place across the walls of millions of tiny air sacs called alveoli, which are surrounded by capillaries.
Explain how the alveoli are adapted to allow efficient gas exchange between the air and the blood. (6 marks)
Small organisms can exchange gases over their whole body surface, but large animals need specialised exchange surfaces such as lungs. This is related to the surface-area-to-volume ratio.
Two cube-shaped model "organisms" are compared. Cube A has sides of 1 cm; cube B has sides of 2 cm.
(For a cube of side L: surface area =6L2 and volume =L3.)
(a) Calculate the surface-area-to-volume ratio of cube A and of cube B. Show your working. (3 marks)
(b) Using your answers, explain why a large animal cannot rely on diffusion across its outer surface alone to supply all its cells with oxygen. (1 mark)
Arteries and veins are two types of blood vessel with different structures suited to their functions.
(a) Give one structural difference between an artery and a vein, other than the presence of valves. (1 mark)
(b) Explain why veins have valves but arteries (in general) do not. (2 marks)
The food chain below is part of a woodland community.
oak leaves → caterpillars → blue tits → sparrowhawks
A disease kills most of the blue tits in the wood one year.
(a) Suggest and explain what would happen to the population of caterpillars soon after the blue tits die. (2 marks)
(b) State what the arrows in a food chain represent. (1 mark)
During a sprint, an athlete's leg muscles cannot get enough oxygen and begin to respire anaerobically.
Compare anaerobic respiration in muscle cells with aerobic respiration, in terms of the products formed and the amount of energy released. (2 marks)
In a pond, all the perch (one species of fish) living there at a particular time make up a group of organisms studied by ecologists.
Name the term used for all the organisms of one species living in a particular area at a particular time. (1 mark)