Some of the Edexcel SNAB core praticles

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  • Created by: sorcha
  • Created on: 12-05-11 09:31


Topic 1

Caffeine on heart rate

·         Use of Daphnia-

o    Because they posses simple nervous system,

o   Because they are see though so you can measure heart rate directly.

·         Ethical

o   Living organisms so you can treat them with respect and you put them back in the pond water

·         Variability

o   Different gender, ages

o   Different sizes

·         Hard to count

o   So fast inaccuracy

·         Light from microscope

o   Light and heat causes stress

·         Acclimatized – take 2 reading and check the readings are the same before experiments.

·         Random-counting heart rate with our eyes

·         Systematic – something with the same degree of error for each result. Eg. Leaving the daphnia to acclimatize for five mins.

·         Independent variable: caffeine conc. Min 5 conc. Of caffeine and control.

·         Repeat exp. To improve reliability

·         Risks: pond water wash  with antibacterial soap your hands so that you



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