Life Chemical Cellular and Evolutionary Foundations A The science of how life and the body works 1 Science is about making observations based on knowledge I What is biology The Scientific Method II A 1 Observation the act of viewing the world around us 2 Hypothesis a tentative explanation for one or more observations a educated guess b Not typically based on a lot of knowledge c A good hypothesis makes predictions about observations not yet made or experiments not yet run d These predictions can be tested 3 Predictions what do you think is going to happen next 4 Experimentation a disciplined and controlled way of asking and answering questions about the world in an unbiased manner a Needs to be unbiased 5 Theory a Once a hypothesis has been supported by a large body of experiments and observations it can become a theory b Theory is only possible if results are consistent over many experiments c Note that in general conversation the term theory is often synonymous with hypothesis d But in science a theory is fact III IV A Case Study on the Scientific Method partner activity over what causes stomach ulcers Types of Experiments 2 A Comparative B Controlled 1 Look at trends in data to make predictions 1 Only one variable is looked at all other are kept controlled 2 Dependent variable is the only one manipulated V What do you think causes ulcers A Stress B Excessive stomach acid C A bad diet D Being overweight E Drinking excessive alcohol VI What Causes Ulcers VII A Possible Study Design A Design an experiment to test if the excess acid hypothesis is true B In small groups design the experiment be specific about how you would treat your groups and what you would measure A Doctors divide patients into two groups 1 Group 1 received antacids and were instructed to take them 3x day 2 Group 2 received sugar pills and were instructed to take them 3x day B After 3 months the number of ulcers per patient is assessed C Predict what the results would look like if the excess acid theory was supported 1 The graph should look a bit like this D Initially this type of experiment was not performed E Patients who took antacids had decreased ulcer symptoms F Symptoms returned in patients that stopped taking the antacids VIII Dr J Robin Warren pathologist A Examines stomach biopsies B Used higher power magnification to look at the slides IX Dr Warren thought he saw A Helicobacter pylori a new species of bacteria 1 The black squiggly spots on the slide are bacteria that Dr Warren observed in his biopsy slides B But no one else believed him C He used a special stain that highlights bacteria on his slides D This convinced his colleagues that the bacteria were there X Dr Warren thinks H pylori causes ulcers A What is another hypothesis to explain why Dr Warren was finding bacteria on his slides there are at least three alternative hypotheses 1 Alternative explanations hypotheses a Contamination happened AFTER b The bacteria lives in the stomach but does no damage c Bacteria are opportunistic and arrive after ulcers have already weakened the stomach s defenses XI Dr Barry J Marshall Joins Dr Warren s Research A Their first survey study 1 100 stomach ulcer patients surveyed biopsy taken 2 100 had H pylori present a This supported Warren s original hypothesis b The real experiment is missing control B Hypothesis Bacteria CAUSE stomach ulcers C What experiment would you design if you wanted to test this hypothesis D Based on this they performed an experiment in which all the patients were treated with antibiotics to see if this would cure the ulcers 1 What is missing from this experiment a CONTROL XII Prediction of Results A If they set up their antibiotic with a treatment group Exptl who received antibiotics and a control group Con who received a placebo no antibiobiotics what results would expect if the original excess acid hypothesis was supported 1 Results Expected B What results would you expect if the bacteria cause ulcers hypothesis was supported 1 Results Expected XIII Actual Results of Warren Marshall s Study A When treated with antibiotics 80 of patients were permanently cured of their ulcers XIV To Further Demonstrate Cause and Effect A Dr Marshall swallowed a flask of H Pylori 1 Within a week he was suffering from symptoms of H Pylori 2 He then cured himself with an antibiotic treatment B Today about 50 of people have H Pylori infections but not all have stomach ulcers XV Characteristics of Living Organisms 6 A Must consist of one or more cells B Must contain genetic information C Must be capable of reproduction D Must be capable of metabolism E Must be capable of homeostasis 1 Homeostasis the ability to maintain a constant internal environment in response to environmental changes F Must be genetically related and have evolved XVI Francesco Redi Experimentation A One of the first experiments to prove spontaneous regeneration does NOT happen B The scientific method proves that living organisms come from other living organisms C Francesco Redi tested this hypothesis in the 1600s by proving that maggots come from flies laying their eggs 1 In this experiment a Three jars with meat differed only in their covering open jar gauze covered jar and sealed jar b Redi observed that only the jar that was left open became covered in maggots because flies were allowed to lay their eggs on the meat c These results support the hypothesis that living organisms come from other living organisms life does not spontaneously arise from nonliving materials XVII Louis Pasteur Experimentation A In the 1800s Louis Pasteur tested the hypothesis that microorganisms can arise by spontaneous generation 1 In this experiment he used sterilized broth in a straight neck flask and in a swan neck flask a The straight neck flask allowed dust particles carrying microbes to fall into the sterile broth b The swan neck flask prevented dust from getting inside B Pasteur rejected the hypothesis that microbes arise spontaneously from sterile broth Instead exposure to microbes carried on airborne dust particles is necessary for microbial growth C XVIII Cells XIX ESSENTIAL FEATURES OF A CELL A The simplest self replicating entity that can exist as an independent unit of life B Cell Sizes and Shapes Vary C Most cells are tiny with their dimensions well below the threshold of detection by the naked eye yet there are some specialized cells that are quite large D Each of these cell types contains a stable blueprint of information in a molecular
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