Daphnia are small crustaceans that are inexpensive, easy to care for, and transparent. The latter property allows students to easily observe the beating heart (Figure 1).
Table of Contents
What are Daphnia a level biology?
โโDaphniaโare water fleas, used in this case because they have a โtranslucentโbody through which the heartbeat can be observed, and hence the effect of caffeine on heart rate can be measured. Equipment.
Why does caffeine increase heart rate in Daphnia?
We hypothesized by increasing the amount of caffeine the heart rate will also increase because caffeine activates neurotransmitters that excite the body which then increases heart rate. Our study system included each Daphnia used in each specific trial, the two concentrations of caffeine, and the plain water solution.
What factors affect the heart rate of Daphnia answers?
Daphnia is poikilothermic, which means that its body temperature and therefore its metabolic rate are affected directly by the temperature of the environment. The change in metabolic rate is reflected in the rate at which the heart beats (cardiac frequency).
What is the independent variable in the Daphnia experiment?
Variables The independent variable was the amount of caffeine we administrated to the daphnia. The dependent variable was the heartbeat of the daphnia before and after their caffeine intake.
What are the characteristics of Daphnia?
Daphnia are planktonic crustaceans that belong to the Phyllopoda (sometimes called Branchiopoda), which are characterized by flattened leaf-like legs used to produce a water current for the filtering apparatus.
Why does alcohol decrease heart rate in Daphnia?
It is assumed based on the similar results we found, that ethanol caused a decreased heart rate because it suppressed the sensitivity of the baroreceptor reflex (Abdel-Rahman et al., 1987). This accounts for the bradycardia found in both the daphnia and the humans.
Why does heart rate increase when temperature increases Daphnia?
As body temperature increases, the rate of chemical reactions and physiological activities within the organism increase. The rate of cellular respiration increases, requiring more oxygen and producing more carbon dioxide. This requires an increased flow of blood, which is pumped by the heart.
Why does Daphnia heart rate decrease with caffeine?
Our Page 2 2 JUBLI 2:2 (2019) hypothesis is that the heart rate of daphnia increases when subjected to caffeine because caffeine is a stimulant and that the heart rate of daphnia slows when subjected to ethanol because it acts as a depressant.
What concentration of caffeine kills Daphnia?
Dab around the Daphnia with a tissue to remove the pond water and replace with drops of caffeine solution (e.g. 0.1M). Leave the Daphnia for 5 minutes to acclimatise and then observe & count (using a counter) the heart rate under the microscope for 30 seconds (multiply number by 2 to calculate beats per minute).
What drugs increase Daphnia heart rate?
We tested the effect of dopamine on the heart rate of Daphnia, and compared its effect with caffeine and ethanol alone and in combination. Both caffeine and dopamine were found to instantly increase the heart rate of Daphnia in a dose-dependent manner.
How does salinity affect Daphnia heart rate?
As salt levels increase, the amount of dissolved oxygen decreases. This means that Daphnia need to breathe more to get enough oxygen, and this means an increase in heart rate (Tan, 2015).
Do Daphnia like warm or cold water?
The cold condition gave the daphnia a higher heart rate than the control, and the extremely cold water gave the daphnia the highest heart rate of all the conditions. We made the observation that in the room and extremely cold water temperatures the heart rate decreased throughout the trials.
Why do Daphnia suffer heat stress?
Heat stress of Daphnia magna results in initial stimulation of thoracic limb activity and its subsequent decrease at sublethal temperature (Paul et al., 2004). Heat stress increases metabolic rate and oxygen demands in poikilothermic organisms.
What temperature do Daphnia live in?
Temperature is one of the most important environmental factors for Daphniaand should remain near 70ยฐF for successful breeding. Also, the pH of the water should be kept at 7 to 8.5.
How is Daphnia heart rate measured?

What objective should one use to observe the Daphnia under the microscope?
The Daphnia should live for a while like this, as long as there is the right amount of water on the slide. View with 4x or 10x objectives on a compound microscope and adjust focus carefully to see different features.
Does pond water decrease Daphnia heart rate?
Daphnia were cooled on ice before the experiment. Beakers containing Daphnia in pond water were put on ice for about half an hour. This had the effect of slowing the heart rate and thus facilitating counting.
What type of water do Daphnia live in?
Daphnia can be found in almost any permanent body of water. They are mainly freshwater and densely populate most lakes and ponds. They live as plankton in the open water of lakes, or live either attached to vegetation or near the bottom of the body of water (Miller, 2000).
What is the role of Daphnia?
Daphnia plays a central role in lake pelagic ecosystems not only down the food web as a grazer, but also up the food web as an important prey for predatory invertebrates and planktivorous fish [31].
Why are Daphnia called water fleas?
Daphnia are filter feeders that direct small suspended particles into their mouth by a water current produced by their leaf-like legs (Figure 1). Daphnia’s common name of ‘water flea’ comes from its jump-like movement, which results from the beat of the large antennae used for swimming (Figure 1).
What is the relationship between alcohol and the heart rate in Daphnia?
Alcoholic beverages have decreasing effect on the heart rates of Daphnia. As the concentration of alcoholic beverages increases, the heart rate of Daphnia decreases.
How does caffeine affect the heart rate of Daphnia independent variable?
The independent variables are the seven caffeinated solutions that are tested on the Daphnia magna. It is hypothesized that caffeine solution with higher concentrations of caffeine will cause two effects: an increase in heart rate and a higher increase of heart rate in pregnant Daphnia compared to nonpregnant Daphnia.
What conditions do Daphnia need to survive?
Daphnia typically reproduce well with 12 hours of light and 12 hours of darkness a day. Be sure that any artificial light does not significantly heat the water in the container. The temperature of the water should remain near 70ยฐ F to promote successful breeding.
Do Daphnia have similar hearts to humans?
Daphnia magna are known to have hearts that are comparable to human hearts. The Daphnia are used to test the effect of different substances on their heart rate to see a similar effect that would be in the human heart.