Get Ready for A & P! The Scientific Method Get Ready for A & P! The Scientific Method

Biology  Scientific study of life  Lays the foundation for asking basic questions about life and the natural world  Anatomy & Physiology is one branch of biology

Why Study Biology?  To learn how organisms are constructed, how they function, where they live, and what they do  To help develop, modify, and refine ideas about life

How do we study Biology?   Biology is studied using the scientific method   Different than other modes of study because it has specific steps and rules

What is the Scientific Method?  Observe phenomenon  Develop hypotheses  Make predictions  Devise test of predictions  Carry out test and analyze results  Publish results so others can repeat

Inductive Logic  Using observations and facts to arrive at generalizations or hypotheses - begins the scientific method  Observation: Eagles, swallows, and robins have feathers  Hypothesis: All birds have feathers

Deductive Logic  Drawing a specific conclusion based on a generalization - after testing a hypothesis Generalization - Birds have feathers Generalization - Birds have feathers Example - Eagles are birds Example - Eagles are birds Conclusion - Eagles have feathers Conclusion - Eagles have feathers

Role of Experiments  Used to study a phenomenon under known conditions  Allows you to predict what will happen if a hypothesis is supported  Can never prove a hypothesis 100% correct

Experimental Design  Control group A standard for comparison A standard for comparison Identical to experimental group except for variable being studied Identical to experimental group except for variable being studied  Sampling error Nonrepresentative sample skews results Nonrepresentative sample skews results Minimize by using large samples Minimize by using large samples

Biological Therapy Experiments Can we use viruses that attack bacteria (bacteriophages) to fight infections?

Experiment 1  Hypothesis - Bacteriophages can protect mice against infectious bacteria  Prediction - Mice injected with bacteriophages will not die as a result of bacterial injection

Experiment 1 - Test Experimental group Experimental group Inject with bacteria and bacteriophage Inject with bacteria and bacteriophage Control group Control group Inject with bacteria and saline

Experiment 1 - Results & Conclusion  Experimental group All mice lived  Control group All mice died  Conclusion - Bacteriophage injections protect mice against bacterial infections

Experiment 2  Prediction - Bacteriophage injections will be a more effective treatment than a single dose of the antibiotic streptomycin  Test - Mice injected with bacteria, then with saline, streptomycin, or bacteriophage

Experiment 2 - Results  With 2nd injection: Bacteriophage - 11 of 12 mice lived Bacteriophage - 11 of 12 mice lived 60 mg/gm streptomycin - 5 of 12 lived 60 mg/gm streptomycin - 5 of 12 lived 100 mg/gm streptomycin - 3 of 12 lived 100 mg/gm streptomycin - 3 of 12 lived Saline - all mice died Saline - all mice died  Conclusion - Bacteriophage treatment can be as good or better than antibiotic treatment

Minimizing Variables  All mice were same age and sex, reared under same conditions  Each mouse in each test group received exact same treatment  All mice in control group received same amount of saline  Variable tested was antibiotic treatment versus bacteriophage treatment

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Results Control Group: Some get intestinal cramps Experimental Group: Some get intestinal cramps Experiment Control Group: Eats regular potato chips Experimental Group: Eats Olestra potato chips Fig. 1-10, p.12 Hypothesis Olestra® causes intestinal cramps. Prediction People who eat potato chips made with Olestra will be more likely to get intestinal cramps than those who eat potato chips made without Olestra Conclusion Percentages are about equal. People who eat potato chips made with Olestra are just as likely to get intestinal cramps as those who eat potato chips made without Olestra. These results do not support the hypothesis.

Scientific Theory  A hypothesis that has been tested for its predictive power many times and has not yet been found incorrect  Has wide-ranging explanatory power Darwin’s theory of evolution by natural selection Darwin’s theory of evolution by natural selection The Cell theory - all living things are made of cells The Cell theory - all living things are made of cells

Scientists Raise Questions The external world, not internal conviction, must be the testing ground for scientific beliefs

Limits of Science  Scientific approach cannot provide answers to subjective questions  Cannot provide moral, aesthetic, or philosophical standards  Conflict with supernatural beliefs Copernicus Copernicus Darwin Darwin