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

What these 13 flashcards ask

Why do arteries have elastic fibres?
Why do veins have valves?
How is a capillary adapted for exchange?
Why is the lumen of a vein wide?
Why is Daphnia used in the caffeine practical?
What is the independent variable in the Daphnia practical?
Name three variables to control in the Daphnia practical.
Why are cotton wool fibres placed on the slide?
How do you convert a count of beats in 20 s to beats per minute?
How is percentage increase calculated?
What is the effect of caffeine on Daphnia heart rate?
Why might using invertebrates in research be considered more ethical than using mammals?
What do replace, reduce and refine mean?

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

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
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
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

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).