Photo AI
The water flea, Daphnia pulex, is a small invertebrate animal that lives in ponds - Scottish Highers Human Biology - Question 11 - 2019
Question 11
The water flea, Daphnia pulex, is a small invertebrate animal that lives in ponds. Water fleas can be used as model organisms to investigate the effect of chemicals... show full transcript
Worked Solution & Example Answer:The water flea, Daphnia pulex, is a small invertebrate animal that lives in ponds - Scottish Highers Human Biology - Question 11 - 2019
Step 1
Suggest why the student left the water flea in the solution for 5 minutes before videoing its heart rate.
Answer
The student left the water flea in the solution for 5 minutes to allow it to acclimatize to the new conditions. This time enables the flea’s heart rate to stabilize and return to its resting rate, ensuring that the measurement is accurate.
Step 2
Step 3
Use data from the table to describe the changes that occur in the heart rate as the caffeine concentration increases.
Answer
As the caffeine concentration increases from 0 g/l to 0.8 g/l, the heart rate of the water flea rises from 135 bpm to 270 bpm. Specifically, it shows an increase of 135 bpm over this range. However, at a concentration of 1.0 g/l, the heart rate remains constant at 270 bpm, indicating that the increase in heart rate levels off.
Step 4
State how the reliability of the results from this investigation could be improved.
Answer
The reliability of the results could be improved by repeating the investigation with more water fleas. This repetition could help to account for any variability in individual heart rates and yield more consistent data.
Step 5
In humans, describe how the autonomic nervous system increases the heart rate.
Answer
The autonomic nervous system increases heart rate through various mechanisms. It controls the heart via the sinoatrial node (SAN), which sends signals across the atria to the atrioventricular node (AVN). Additionally, sympathetic nerves release noradrenaline, stimulating the heart to increase its rate. This response is crucial during activities that require heightened cardiovascular performance.