The Nature of Science. Chapter 2 DE Biology (Bio115)

Transcription

1 The Nature of Science Chapter 2 DE Biology (Bio115)

2 2.1 How Would a Scientist Investigate Childbed Fever? Ignaz Semmelweis - Hungarian, Born 1818 in Budapest - fifth of 10 children - Degree in Obstetrics Work in Division 1 of the Allgemeines Krankenhaus

3 Looking for Clues - Gather Data: records of births and childbed-feverrelated deaths at the hospital. - Division 1 (male doctors): 2.5x higher - Division 2 (female midwifes) - Home birth: low chance of fever

4 Possible Causes Miasma:harmful, toxic vapor supposedly exhaled by sick people or exuded by garbage or sewers increase the ventilation - no sig change Birthing position? no sig change Rough Male Medical Students? reduce # of medical students - no sig change Cadaverous Particles wash hands between procedures - sig change

5 Possible Causes Cadaverous Particles are known today as Microorganisms: a living thing that cannot be seen without the use of a microscope, such as bacteria Childbed fever caused by Streptococcus pyogenes. S. pyogenes causes strep throat, scarlet fever, rheumatic fever and a variety of skin infections.

6 Scientist Spotlight Robert Koch ( ) - Skillful physician but sought scientific research - Researched anthrax, a deadly scourge for farm animals and farmers. - Injected mice with infected and uninfected blood to prove the cause of disease is bacteria - Developed pure cultures - Form spores when conditions are poor and remain dormant until opportunity to infect arrives - Biological Weapon

7 2.2 How Does Science Work? Scientific method: set of procedures scientists use in their investigations; includes four steps: observation and facts, hypotheses and predictions, testing, and evaluation and interpretation of results.

8 Observations and Facts Observations: what you can see, hear, smell, taste, or feel physically Facts: things that you know to be true Semmelweis observed 2 facts: 1) Deaths due to childbed fever had higher incidence in the hospital than outside 2) Within the hospital, the incidence was higher in Division 1 than in Division 2

9 Hypotheses and Predictions Hypothesis: possible cause or mechanism that could explain observations and facts Prediction: educated speculation about what an outcome will be Ex: Semmelweis prediction that miasma causes childbed fever Scientific predictions: if the hypothesis is correct, then a certain set of conditions should yeild a certain set of results

10 Testing Test: a procedure that sets up the conditions the predictions require. Ex: Semmelweis tested his hypothesis by adding ventilation, changing the birthing position, decreasing the number of male physicians and washing hands REQUIRED Controlled experiment: a test or manipulation in which a scientist keeps all variables (possible factors that could affect the outcome of the test) the same except for the one under investigation

11 Evaluation and Interpretation of Results - Is the experiment repeatable? - often 3 is the magic number (experiments done in triplicates) - Can the experiment be communicated to other scientists through a paper or a presentation? - Evidence can only support your hypothesis NOT prove it with absolute certainty

12 Scientific Theories Newton s Theory of Gravity Charles Darwin s Theory of Natural Selection Albert Einstein s Theory of Relativity

13 Scientific Theories Theory: an idea, supported by evidence, which provides a bigger picture than a hypothesis of how some aspect of nature works; it may weave together supporting evidence from several scientific fields Darwin s Theory of Natural Selection - General Theory of how all organisms evolved - Tie together to one theory

14 2.3 What Assumptions Does Science Make About Nature Cause and effect: every event or outcome in nature has a source; if a scientist sets up the correct conditions, the results can be predicted in advance Events are consistent and repeatable self-correcting Materialism: the idea that effects the natural world all have natural causes, rather than supernatural ones.

15 2.4 What are the Principal Features of Science Empirical evidence: information that one gets from direct observation, from experience, or from the results of experiments and other tests of hypotheses. + Every scientific hypothesis and theory is evaluated strictly by how well it explains the existing empirical evidence. Testability: a procedure for determining the evidence in support of a hypothesis Falsifiable: able to be proved wrong

16 2.4 What are the Principal Features of Science Generality: how widely a scientific investigation applies to situations other than specific ones scientists tested. ex: ExoS/ChvI - signalling pathway similar to pathways in pathogenic bacteria.

17 2.5 How does Science Differ from Other Ways of Knowing? Science and religion do not need to be in conflict because they answer different questions Scientists are not going to answer questions about the metaphysical and spiritual domains - a divine being - afterlife Religious scripture and leaders are not - reincarnation going to answer questions about the natural world - a tumor forms - ice cap melts - male pattern baldness exists

18 2.6 How does Science differ from Pseudoscience and Quackery? Pseudoscience: fake science that appeals to emotion, sentiment or distrust of established knowledge. Quackery: promoting the use and/or purchase of remedies even when there is no scientific evidence or plausible rationale for their effectiveness. Ex: tarot readings, astrology, health fads

19 2.6 How does Science differ from Pseudoscience and Quackery? - Creationism: idea that a divine being created all species in a single event = pseudoscience - can t be tested by controlled studies - evidence is often ignored - Geological record, fossil record, evidence from embryos and molecular studies all confirm the theory of evolution