Daphnia Research Paper
Lesson Organisation
This will depend on the number of microscopes you have and access to a healthy culture of Daphnia. Students can readily follow this procedure working in pairs. Because of the variability of results between individual Daphnia it is not appropriate to make conclusions from one set of results, so each pair (or group) of students should carry out more than one investigation to contribute to the class set.
One option is to record a live video of a sample Daphnia, during a time period in which students count the heart beats. Then, you can replay the video in slow motion and count the heart beats again. This allows students to consider the accuracy of their counting.
If your time or access to chemicals is limited, you could …show more content…
This occurs after feeding, during sleep, and during breath-holding and swimming underwater. A slowed heart rate and the associated fall in the rate of ejection of blood from the heart is sufficient to maintain body function during rest, and conserves energy in the heart under conditions where its supply (and the supply of oxygen in the blood) are diminished. A drug that slows heart rate is called a negative chronotrope and this is demonstrated in this experiment where acetylcholine is used to slow the rate of the Daphnia's …show more content…
By a different mechanism (that doesn't involve beta-1 adrenoceptors), caffeine also increases the amount of cAMP in the sinoatrial node. Then cAMP levels increase and this increases the electrical activity of the sinoatrial node, making it depolarize and 'beat' faster. Caffeine has additional effects on the heart. Like adrenaline and noradrenaline, it can affect the main pumping chambers (ventricles) leading to an increase in the rate of contraction and relaxation of each heart beat. This means that as well as beating faster, the heart's individual beats are associated with an increased volume of blood ejected into the circulation per unit time. This is called increasing cardiac output. Two or three cups of strong coffee or tea contain enough caffeine (and a similar acting compound called theobromine) to cause an increase in human heart rate of 5-20 beats/min.
Ethanol: Ethanol slows heart rate. At the concentrations used in this experiment ethanol depresses the nervous system by acting as what is known as a nonselective neurodepressant. The amounts of ethanol necessary to achieve this effect in humans would be sufficient also to depress the respiratory centres of the brain, rather like the effect of an overdose of general anaesthetic, resulting in
This will depend on the number of microscopes you have and access to a healthy culture of Daphnia. Students can readily follow this procedure working in pairs. Because of the variability of results between individual Daphnia it is not appropriate to make conclusions from one set of results, so each pair (or group) of students should carry out more than one investigation to contribute to the class set.
One option is to record a live video of a sample Daphnia, during a time period in which students count the heart beats. Then, you can replay the video in slow motion and count the heart beats again. This allows students to consider the accuracy of their counting.
If your time or access to chemicals is limited, you could …show more content…
This occurs after feeding, during sleep, and during breath-holding and swimming underwater. A slowed heart rate and the associated fall in the rate of ejection of blood from the heart is sufficient to maintain body function during rest, and conserves energy in the heart under conditions where its supply (and the supply of oxygen in the blood) are diminished. A drug that slows heart rate is called a negative chronotrope and this is demonstrated in this experiment where acetylcholine is used to slow the rate of the Daphnia's …show more content…
By a different mechanism (that doesn't involve beta-1 adrenoceptors), caffeine also increases the amount of cAMP in the sinoatrial node. Then cAMP levels increase and this increases the electrical activity of the sinoatrial node, making it depolarize and 'beat' faster. Caffeine has additional effects on the heart. Like adrenaline and noradrenaline, it can affect the main pumping chambers (ventricles) leading to an increase in the rate of contraction and relaxation of each heart beat. This means that as well as beating faster, the heart's individual beats are associated with an increased volume of blood ejected into the circulation per unit time. This is called increasing cardiac output. Two or three cups of strong coffee or tea contain enough caffeine (and a similar acting compound called theobromine) to cause an increase in human heart rate of 5-20 beats/min.
Ethanol: Ethanol slows heart rate. At the concentrations used in this experiment ethanol depresses the nervous system by acting as what is known as a nonselective neurodepressant. The amounts of ethanol necessary to achieve this effect in humans would be sufficient also to depress the respiratory centres of the brain, rather like the effect of an overdose of general anaesthetic, resulting in