Wormbeat Lab

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by Hebert2
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Wormbeat Lab

Wormbeat Lab

Background FactsTo conduct the Wormbeat Lab:1) The worm must be calm enough to find it's pulse. Students must be able to identify the worm's pulse and count the amount of contractions over the course of a minute.2) There must be a controlled variable in the experiment in order to identify what it is that changes the worm's pulse. In the case of this experiment, the temperature.3) Students must know that Earth Worms are ectotherms, meaning they use outside temperatures to regulate their body temperatures. This means that decreasing the temperature of the environment will correlate with the worm's pulse, directly or indirectly.

Question:How will changing the temperature affect an earthworm's heart rate?

IDV: The independent variable is the temperature.DV: The dependent variable is the worm's heart rate.

Hypothesis:If the heart rate of earthworms is affected by temperature, then the earthworm's heart rate should decrease as the temperature declines.

One Pulse

Conclusion:1) The temperature and the worm's heart rate are directly correlated, meaning as the temperature declines, the worm's heart rate decreases.2) The class average worm heart rate at room temperature (20-23.5 degrees Celsius) was 17.6 beats per minute. The class average worm heart rate at 10 degrees Celsius was 10.6 beats per minute.3a) These results make sense when dealing with worms, which are ectotherms. Ectotherms regulate body heat by slowing blood flow to retain heat and speeding blood flow to release heat. When an ectotherm gets too cold, it slows blood flow to retain heat. If the worm sped up or kept constant blood flow, it would freeze due to the circulation of cold blood. It's body temperature would decrease dangerously low if it did not slow it's blood flow.3b) The results from the Wormbeat Lab would not hold true for humans. Humans are endotherms; endotherms maintain body temperature through metabolic changes. When the body gets too cold, metabolism speeds up and the body begins to shiver. Shivering is the body's muscles contracting in attempt to keep warm. The muscle contractions require more oxygen to function, in turn blood flow increases. To allow for more blood flow the heart pumps faster, increasing heart rate. Humans and earthworms differ in reactions to the cold, where a worm's heart rate decreses, a human's would increase.


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