Blood vessels and the Daphnia heart-rate practicalEdexcel A-Level Biology A: Mind map

Exam questions on Blood vessels and the Daphnia heart-rate practical

1. Blood leaving the left ventricle of a mammal travels through an artery, then arterioles, then capillary networks in the muscles. It returns to the heart through venules and a vein.
   Explain why the wall of an artery contains elastic tissue.2 marks
2. A student investigates the effect of caffeine on the heart rate of Daphnia. She places one Daphnia in a drop of caffeine solution on a cavity slide, with a few cotton wool fibres to restrict its movement, and counts the heartbeats seen under a microscope in 20 s.
   In the control, the student counted 56 beats in 20 s. Calculate the heart rate in beats per minute.2 marks
3. The student repeated the investigation using five Daphnia in each of four caffeine concentrations. The mean heart rates were 186 beats per minute in 0.0 %, 201 in 0.1 %, 219 in 0.2 % and 255 in 0.4 % caffeine solution.
   Describe the effect of caffeine on heart rate and calculate the percentage increase in heart rate between 0.0 % and 0.4 % caffeine.3 marks