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Friedrich Wohler, 1828

Friedrich Wohler, 1828. (NH 4 ) 2 SO 4 + KOCN CH 4 N 2 O + KSO 4 Ammonium + Potassium UREA + Potassium sulphate cyanate sulphate

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Friedrich Wohler, 1828

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  1. Friedrich Wohler, 1828 (NH4)2SO4+ KOCN CH4N2O + KSO4 Ammonium + Potassium UREA+ Potassium sulphate cyanate sulphate Inorganic + Inorganic ORGANIC+ Inorganic Eduard Buchner, 1897 Yeast cell contents (enzymes) Sugar Alcohol

  2. Pseudoscience

  3. Key Steps in the Scientific Method • Observe, define and measure the subject of enquiry • Hypothesis – develop a hypothetical explanation for your observations and measurements • Prediction • Experiment

  4. The Scientific Method is Iterative • Define a question • Gather information and resources (observe) • Form an explanatory hypothesis • Perform an experiment and collect data, testing the hypothesis • Analyze the data • Interpret the data and draw conclusions that serve as a starting point for new hypothesis • Publish results • Retest (frequently done by other scientists)

  5. Louis Pasteur 1822-1895 Fermentation Pasteurization Rabies Vaccine Fowl cholera vaccine Anthrax vaccine Silk worm disease Germ theory/spontaneous generation

  6. Fowl Cholera X + A fresh culture of Pasturella multocida

  7. Observation 1 + An ‘old’ culture of P. multocida

  8. Question/hypothesis + ‘Old’ P. multocida Why do the chickens survive? Is it because ‘old’ rather than ‘fresh’ bacteria were used?

  9. + + ‘Old’ P. multocida ‘Fresh’ P. multocida Observation 2 When the chickens were then injected with ‘fresh’ bacteria – they survived! New hypothesis: Injection with ‘old’ bacteria protects the chickens against subsequent infection with ‘fresh’ bacteria. .

  10. + + ‘Old’ P. multocida ‘Fresh’ P. multocida Observation 2 BUT the chickens may have survived because: they were protected by the first injection of ‘old’ bacteria? of a change in diet between the 1st and 2nd injections? they were older when they received the 2nd injection? the weather was better when they received the 2nd injection? We need a 2nd group of chickens that are handled the same way as the first as regardsage, diet, crowding etc but which do not receive the injection of ‘old’ bacteria. This is thecontrolgroup. We test 1 variable.

  11. + + ‘Old’ P. multocida ‘Fresh’ P. multocida Experiment Group I – the experimental group. We predict these chickens will survive. Group II – the control group. We predict these chickens will die. X + Mock injection ‘Fresh’ P. multocida

  12. Outcome In this case the predictions were correct thus the hypothesis is SUPPORTED (but not proven). If there was no difference between the two groups the hypothesis would have been DISPROVED. A hypothesis can NEVER be proven as there are too many variables to contend with in one experiment ie humidity, genetic background etc.

  13. Formal hypothesis “Ifleaf color change is related to temperature, thenexposing plants to low temperatures will result in changes in leaf color” The dependent variable is the one you observe and/or measure The independent variable is the one that you control

  14. Formal hypothesis Ifskin cancer (dependent) is related to ultraviolet light (independent), then people with a high exposure to UV light will have a higher frequency of skin cancer. Ifbacterial death is related to penicillin, then exposing bacteria to increasing concentrations of penicillin will increase the number of bacteria killed.

  15. Null hypothesis A null hypothesis is a hypothesis set up to be nullified or refuted in order to support an alternative hypothesis. The null hypothesis is presumed true until experimental evidence indicates otherwise.

  16. Fig. 2.3 The structure of atoms found in organisms

  17. Electronegativity is a measure of the ability of an atom or molecule to attract electrons in the context of a chemical bond.

  18. Fig. 2.3 The structure of atoms found in organisms

  19. Fig 2.12 Water is polar and participates in hydrogen bonds

  20. Fig 2.13

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